Digital BW, The Print

Hooray, Claude! Very well said.



Bill Kennedy
Associate Professor of Photocommunications
St. Edward's University
512/448-8680


[Non-text portions of this message have been removed]

Norman Koren has a great site that explains everything in detail, but is not
for the faint of heart. It requires careful study. While there is a lot of
great info on the site, this link gets you to the dynamic range questions
you are asking about.

http://www.normankoren.com/digital_tonality.html

His site also does a technical comparison of digital and film cameras for
resolution and noise, including the limiting effects of lens resolution. For
digital there is only one lens, but for film there are three lenses of
interest - the camera lens, a scanner lens, or the enlarger lens. It's a
fascinating website. Here is the link for that discussion.
http://www.normankoren.com/Tutorials/MTF.html

Steve

----- Original Message ----- 
From: "Steve Kale" <stevekale@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Tuesday, November 23, 2004 2:09 AM
Subject: Re: [Digital BW] Tonal range recording



Ok so I must confess that this and the other responses blew straight over my
head, not being a zone guy and not understanding film shoulders and toes.
Can I ask some basic questions so that I can follow the discussion:

1)  You speak of 15 stops from colour negative film.  I have heard people
saying that Velvia slide film has just +/- 1 2/3 stops, or 3 1/3 stops, of
workable range.  Are these measurements of the same thing?  (What is the
tonal range of Provia?)

2) How does one convert stops to density? Loosely.  For example, if a
scanner has a rated dMax of 4.8 how does that relate to the tonal range in
stops of film that it is going to scan?

3) Where does the "12 stop linear capability of some censors" come from?
What is the figure for the 1Ds MK II or 1Ds?

4) I think I understand the importance of linearity - kind-of-sort-of - from
printing.  Is this a similar concept? Ie evenly distributed tonal range?

5) At the end of the day we are severely constrained by the tonal range
capability of our printing.  Hogarth mentioned 8 stops for silver gelatin
paper.  How do I relate a linearised print of a step wedge on HPR with a
paper white dMin of .04 and a best black dMax of 1.68 to these figures?
(Wouldn't it be nice if they all used the same scale?)

While the boundaries of the digital print are expanding, I guess we still
need to shoot by compressing the tonal range of the scene with ND filters
(or multiple exposures) so that it can be rendered well in the print -
traditional or inkjet.  I am trying to relate the two (and the steps that
may be in between eg scanning) so that when I get out my spot meter I am not
only thinking in terms of stops but also in terms of my printer's tonal
range.  Sorry if these are basic questions but I think it will help a lot of
people tie all the talk of dMax back to the camera itself.


Thanks

Steve

PS:  this was not meant to be a digital capture vs film capture discussion -
I think the topic relates to both. I do believe there are significant
workflow efficiencies with digital cameras and I am about to make the switch
but relating the tonal range of a scene as measured by a spot meter in
f-stops back to the tonal range of the printer, ink and paper combination
applies to both forms of capture.


> From: <claudej1@...>
>
>
>
> Boy, you have opened a big can of worms here. Most of the color negative
> film (normal C-41 development) has a Contrast Index of 0.44-0.52, which
means
> a
> 1 stop luminance change in the scene records a 0.14 change in density in
the
> film. Assuming no major color crossovers, from a pure monochomatic
conversion
> of  the resultant lumped densities, you can get out to about 15 stops of
> luminance  before a shoulder apperars from the straight line and short toe
of
> color
> neg.  films. This from a Dmin in the shadows of about .25 to a Dmax of r
2.38
> in the  highlights.
>
> B&W films, especially Tmax (per my curve tests circa 1990) can vary  from
> 3-11 stops with D-76 straight (I wild combinaton to tame I might add) and
a
> 5-11
> minute development time. So with B&W, the Contrast Index (CI) varies  with
> development, as does the effective shadow thresholld speed, although not
as
> much as you might think.
>
> ISO states that you need a CI of 0.65 to get the box speed rating. Most
> Zoners develop their filme to a CI of 0.55 to match to the CI of #2 paper,
> which
> is a CI of 1.8 in an ideal world. So ISO essentially "pushes" the film a
> little  to get their rating, but real users have always derated their film
at
> least
> 2/3  stop with their "normal development."  So, with severe speed derating
> and  an extreme development "pull" you can get a lower CI than color neg.
> film,
> which  is fixed. This could also inhibit the Dmax of the film depending on
the
>  developer and how it is agitated.
>
> I have achieved densities in excess of 4.0 with Tmax developed in Dektol
> (not a misprint), but I never tested for linearity.
>
> So, the recordable density range for B&W film varies all over the map  and
is
> not necessarily superior to the 12 stop linear capability of some
sensors.
> Besides, with digital capture, you can easily increase the dynamic  range
with
> a separate highlight and shadow range exposure to be blended later in  any
> ratio you wish.
>
> This makes blanket statements, in either case, untrue without specific
> details of each method.
>
> I prefer the speed and efficiency of digital capture with the
> creative/corrective post processes afforded by Photoshop, but that's just
me.
> I'm too
> impatient to go back to the darkroom for any reason. I earn my living
with
> "click
> to print" workflows of less than 1 minute for a 4x6 color print from  high
> speed dye subs, and I'm starting to do the same with Epsons, so maybe I've
> been
> pulled too far the other way by digital technology.
>
> I simply love color pigments AND BO/Quad/Hex/Sept/Oct monochrome inkjet
> output on various papers. What a great time to be in the "lightroom" with
so
> many
> great choices.
>
> My handcuffs are long gone along with my toxic chemical dependency.
>
> Claude
>
>
> [Non-text portions of this message have been removed]
>
>
>
>
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
>
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the
membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from
the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner
and
> Moderators. See \u201eGroup Topic, Rules and Guidelines\u2030 in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
>
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE \u201eOWNER\u2030 AND
> \u201eMODERATORS\u2030 OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO
YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  \u201eOWNER\u2030 AND
\u201eMODERATORS\u2030 OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF
SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL
BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON
THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO
THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>
> Yahoo! Groups Links
>
>
>
>
>
>
>





Please visit the Group Homepage to check the Files, and other resources as
they are often being updated.

http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint

If you wish to receive no emails or just a daily digest, or you wish to
unsubscribe, please edit your Membership preferences by visiting this same
page.

Please follow these basic guidelines:
- As threads develop, trim off excess portions of earlier messages to keep
them short.
- Good manners are required at all time. No personal attacks or flames.
Hostile, aggressive or argumentative users may be removed from the
membership without notice.
- Keep your posts and threads related to the group topic of digital B&W
printing. Users who persistently make off-topic posts may be removed from
the membership.
- By posting on this forum you agree to abide by the group rules and
guidelines, and to abide by the actions and decisions of the group Owner and
Moderators. See Group Topic, Rules and Guidelines in the Files section:
http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/

BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE OWNER AND
MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
GOODWILL, USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  OWNER AND
MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY
TO USE THE DIGITAL BW, THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR
ALTERATION OF YOUR TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY
THIRD PARTY ON THE DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER
MATTER RELATING TO THE DIGITAL BW, THE PRINT YAHOO GROUP.

Yahoo! Groups Links

Since no one else better qualified has answered your questions, I'll take a
stab at answering some of them.

> 1)  You speak of 15 stops from colour negative film.  I have heard people
> saying that Velvia slide film has just +/- 1 2/3 stops, or 3 1/3 stops, of
> workable range.  Are these measurements of the same thing?  (What is the
> tonal range of Provia?)

I don't know about these exact numbers, I don't use slide film, but in
general they are saying that the film contains a density range equivalent to
15 stops from darkest to brightest areas but the paper can't print that
great a range and still have texture in the darkest areas and the lightest
areas, i.e. the paper doesn't have as great a contrast or density range as
the film. So if a scene containing 15 stops (not likely in real life) is
recorded on film and the film is then printed the printer would have to
choose between losing some of the texture or detail in the darkest areas or
the lightest areas or some portion of each, i.e. compromises would have to
be made because of the narrower contrast range of paper (really good slide
printers dealt with this problem by making contrast reducing masks). All
traditional photographic papers have roughly the same contrast range, abut
1.8 - 2.1 (Ilfachrome had about the highest at 2.4).  The differences among
them are in how that available range is apportioned among the shadows,
midtones, and highlights, which is what a chracteristic curve will show you.
.

> 2) How does one convert stops to density? Loosely.  For example, if a
> scanner has a rated dMax of 4.8 how does that relate to the tonal range in
> stops of film that it is going to scan?

Density is measured in log units. .30 log units equals one stop. So when I
said above that all papers have a contrast range of about 1.8 to 2.1, that's
saying there's a range of about 6 to 7 stops. I don't know exactly what you
mean by the rest of the question. The 4.8 number in theory is the density in
log units when d max is measured with a reflection densitometer but there
are a lot of variables involved and in any event there's no range as such
with that spec, it's just a measurement.

> 5) At the end of the day we are severely constrained by the tonal range
> capability of our printing.  Hogarth mentioned 8 stops for silver gelatin
> paper.  How do I relate a linearised print of a step wedge on HPR with a
> paper white dMin of .04 and a best black dMax of 1.68 to these figures?
> (Wouldn't it be nice if they all used the same scale?)

Subtract .04 from 1.68 = 1.64 density range. Divide 1.64 by .30 = number of
stops. "They" do all use the same scale or at least the same unit of
measurement once you realize that .30 log units equals one stop. There are
different kinds of step wedges and they usually aren't divided into full
stops. The familiar 21 step wedge is divided into half stops (i.e. .15 log
units per step).

> While the boundaries of the digital print are expanding, I guess we still
> need to shoot by compressing the tonal range of the scene with ND filters
> (or multiple exposures) so that it can be rendered well in the print -
> traditional or inkjet.

Actually I believe the point of Hogarth's message was that he doesn't think
this is necessary when scanning film and printing digitally.  He spoke of
compressing the tonal range by reducing developing times but I would think
his theory is equally applicable to compression by ND filters. Whether he's
correct or not (or whether I'm interpreting what he's saying correctly) I
don't know but it seemed to make sense.

Hope this helps and that I'm not talking down to you..

----- Original Message ----- 
From: "steve_bye" <steve_bye@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Tuesday, November 23, 2004 11:45 PM
Subject: Re: [Digital BW] Tonal range recording


>
> Norman Koren has a great site that explains everything in detail, but is
not
> for the faint of heart. It requires careful study. While there is a lot of
> great info on the site, this link gets you to the dynamic range questions
> you are asking about.
>
> http://www.normankoren.com/digital_tonality.html
>
> His site also does a technical comparison of digital and film cameras for
> resolution and noise, including the limiting effects of lens resolution.
For
> digital there is only one lens, but for film there are three lenses of
> interest - the camera lens, a scanner lens, or the enlarger lens. It's a
> fascinating website. Here is the link for that discussion.
> http://www.normankoren.com/Tutorials/MTF.html
>
> Steve
> ----- Original Message ----- 
> From: "Steve Kale" <stevekale@...>
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Sent: Tuesday, November 23, 2004 2:09 AM
> Subject: Re: [Digital BW] Tonal range recording
>
>
>
> Ok so I must confess that this and the other responses blew straight over
my
> head, not being a zone guy and not understanding film shoulders and toes.
> Can I ask some basic questions so that I can follow the discussion:
>
> 1)  You speak of 15 stops from colour negative film.  I have heard people
> saying that Velvia slide film has just +/- 1 2/3 stops, or 3 1/3 stops, of
> workable range.  Are these measurements of the same thing?  (What is the
> tonal range of Provia?)
>
> 2) How does one convert stops to density? Loosely.  For example, if a
> scanner has a rated dMax of 4.8 how does that relate to the tonal range in
> stops of film that it is going to scan?
>
> 3) Where does the "12 stop linear capability of some censors" come from?
> What is the figure for the 1Ds MK II or 1Ds?
>
> 4) I think I understand the importance of linearity - kind-of-sort-of -
from
> printing.  Is this a similar concept? Ie evenly distributed tonal range?
>
> 5) At the end of the day we are severely constrained by the tonal range
> capability of our printing.  Hogarth mentioned 8 stops for silver gelatin
> paper.  How do I relate a linearised print of a step wedge on HPR with a
> paper white dMin of .04 and a best black dMax of 1.68 to these figures?
> (Wouldn't it be nice if they all used the same scale?)
>
> While the boundaries of the digital print are expanding, I guess we still
> need to shoot by compressing the tonal range of the scene with ND filters
> (or multiple exposures) so that it can be rendered well in the print -
> traditional or inkjet.  I am trying to relate the two (and the steps that
> may be in between eg scanning) so that when I get out my spot meter I am
not
> only thinking in terms of stops but also in terms of my printer's tonal
> range.  Sorry if these are basic questions but I think it will help a lot
of
> people tie all the talk of dMax back to the camera itself.
>
>
> Thanks
>
> Steve
>
> PS:  this was not meant to be a digital capture vs film capture
discussion -
> I think the topic relates to both. I do believe there are significant
> workflow efficiencies with digital cameras and I am about to make the
switch
> but relating the tonal range of a scene as measured by a spot meter in
> f-stops back to the tonal range of the printer, ink and paper combination
> applies to both forms of capture.
>
>
> > From: <claudej1@...>
> >
> >
> >
> > Boy, you have opened a big can of worms here. Most of the color negative
> > film (normal C-41 development) has a Contrast Index of 0.44-0.52, which
> means
> > a
> > 1 stop luminance change in the scene records a 0.14 change in density in
> the
> > film. Assuming no major color crossovers, from a pure monochomatic
> conversion
> > of  the resultant lumped densities, you can get out to about 15 stops of
> > luminance  before a shoulder apperars from the straight line and short
toe
> of
> > color
> > neg.  films. This from a Dmin in the shadows of about .25 to a Dmax of r
> 2.38
> > in the  highlights.
> >
> > B&W films, especially Tmax (per my curve tests circa 1990) can vary
from
> > 3-11 stops with D-76 straight (I wild combinaton to tame I might add)
and
> a
> > 5-11
> > minute development time. So with B&W, the Contrast Index (CI) varies
with
> > development, as does the effective shadow thresholld speed, although not
> as
> > much as you might think.
> >
> > ISO states that you need a CI of 0.65 to get the box speed rating. Most
> > Zoners develop their filme to a CI of 0.55 to match to the CI of #2
paper,
> > which
> > is a CI of 1.8 in an ideal world. So ISO essentially "pushes" the film a
> > little  to get their rating, but real users have always derated their
film
> at
> > least
> > 2/3  stop with their "normal development."  So, with severe speed
derating
> > and  an extreme development "pull" you can get a lower CI than color
neg.
> > film,
> > which  is fixed. This could also inhibit the Dmax of the film depending
on
> the
> >  developer and how it is agitated.
> >
> > I have achieved densities in excess of 4.0 with Tmax developed in Dektol
> > (not a misprint), but I never tested for linearity.
> >
> > So, the recordable density range for B&W film varies all over the map
and
> is
> > not necessarily superior to the 12 stop linear capability of some
> sensors.
> > Besides, with digital capture, you can easily increase the dynamic
range
> with
> > a separate highlight and shadow range exposure to be blended later in
any
> > ratio you wish.
> >
> > This makes blanket statements, in either case, untrue without specific
> > details of each method.
> >
> > I prefer the speed and efficiency of digital capture with the
> > creative/corrective post processes afforded by Photoshop, but that's
just
> me.
> > I'm too
> > impatient to go back to the darkroom for any reason. I earn my living
> with
> > "click
> > to print" workflows of less than 1 minute for a 4x6 color print from
high
> > speed dye subs, and I'm starting to do the same with Epsons, so maybe
I've
> > been
> > pulled too far the other way by digital technology.
> >
> > I simply love color pigments AND BO/Quad/Hex/Sept/Oct monochrome inkjet
> > output on various papers. What a great time to be in the "lightroom"
with
> so
> > many
> > great choices.
> >
> > My handcuffs are long gone along with my toxic chemical dependency.
> >
> > Claude
> >
> >
> > [Non-text portions of this message have been removed]
> >
> >
> >
> >
> > Please visit the Group Homepage to check the Files, and other resources
as
> > they are often being updated.
> >
> > http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> >
> > If you wish to receive no emails or just a daily digest, or you wish to
> > unsubscribe, please edit your Membership preferences by visiting this
same
> > page.
> >
> > Please follow these basic guidelines:
> > - As threads develop, trim off excess portions of earlier messages to
keep
> > them short.
> > - Good manners are required at all time. No personal attacks or flames.
> > Hostile, aggressive or argumentative users may be removed from the
> membership
> > without notice.
> > - Keep your posts and threads related to the group topic of digital B&W
> > printing. Users who persistently make off-topic posts may be removed
from
> the
> > membership.
> > - By posting on this forum you agree to abide by the group rules and
> > guidelines, and to abide by the actions and decisions of the group Owner
> and
> > Moderators. See \u201eGroup Topic, Rules and Guidelines\u2030 in the Files
section:
> > http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> >
> > BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> > YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE \u201eOWNER\u2030 AND
> > \u201eMODERATORS\u2030 OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO
> YOU
> > FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR
EXEMPLARY
> > DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
> GOODWILL,
> > USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  \u201eOWNER\u2030 AND
> \u201eMODERATORS\u2030 OF
> > DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY
OF
> SUCH
> > DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE
DIGITAL
> BW,
> > THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> > TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON
> THE
> > DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO
> THE
> > DIGITAL BW, THE PRINT YAHOO GROUP.
> >
> > Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> >
>
>
>
>
>
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
>
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the
> membership without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from
> the membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner
and
> Moderators. See Group Topic, Rules and Guidelines in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
>
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE OWNER AND
> MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
> GOODWILL, USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  OWNER AND
> MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE
> POSSIBILITY OF SUCH DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY
> TO USE THE DIGITAL BW, THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO
OR
> ALTERATION OF YOUR TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF
ANY
> THIRD PARTY ON THE DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER
> MATTER RELATING TO THE DIGITAL BW, THE PRINT YAHOO GROUP.
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>
>
> Please visit the Group Homepage to check the Files, and other resources as
they are often being updated.
>
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>
> If you wish to receive no emails or just a daily digest, or you wish to
unsubscribe, please edit your Membership preferences by visiting this same
page.
>
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
them short.
> - Good manners are required at all time. No personal attacks or flames.
Hostile, aggressive or argumentative users may be removed from the
membership without notice.
> - Keep your posts and threads related to the group topic of digital B&W
printing. Users who persistently make off-topic posts may be removed from
the membership.
> - By posting on this forum you agree to abide by the group rules and
guidelines, and to abide by the actions and decisions of the group Owner and
Moderators. See Group Topic, Rules and Guidelines in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
>
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE OWNER AND
MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
GOODWILL, USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  OWNER AND
MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY
TO USE THE DIGITAL BW, THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR
ALTERATION OF YOUR TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY
THIRD PARTY ON THE DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER
MATTER RELATING TO THE DIGITAL BW, THE PRINT YAHOO GROUP.

>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>

Hi Steve,

Looks like you're getting different pieces of the puzzle from different people
here.  My contribution is inline below... 

Best regards,

-= mike =-

-----Original Message-----
From: Steve Kale
Sent: 23 November 2004 10:09
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Tonal range recording


Ok so I must confess that this and the other responses blew straight over my
head, not being a zone guy and not understanding film shoulders and toes.
Can I ask some basic questions so that I can follow the discussion:

1)  You speak of 15 stops from colour negative film.  I have heard people
saying that Velvia slide film has just +/- 1 2/3 stops, or 3 1/3 stops, of
workable range.  Are these measurements of the same thing?  (What is the tonal
range of Provia?)

[Mike] Yes they are, so it's very hard to keep any detail in the shadows with
a super-contrasty film like Velvia if you expose correctly for the main parts
of a scene. There are very few colour transparency films with more than five
stops of dynamic range, none (that I'm aware of) with more than six. Provia is
less contrasty than Velvia, and Astia -- my own fave -- is somewhat less
contrasty still.

2) How does one convert stops to density? Loosely.  For example, if a scanner
has a rated dMax of 4.8 how does that relate to the tonal range in stops of
film that it is going to scan?

[Mike] Danger, danger! There is no direct relationship between the two, it
depends upon the characteristics of the film. In the case of colour neg, the
film has a very wide dynamic range (10+ stops as mentioned before) but the
resulting range of density on the film is quite narrow. Conversely,
transparency films can only handle a much narrower range of scene brightness
but the actual density range on the film is much higher, mainly because the
black areas are very dense compared to the densest areas of the highlights on
neg film.

3) Where does the "12 stop linear capability of some censors" come from?
What is the figure for the 1Ds MK II or 1Ds?

[Mike] If you have 12-bit converters in your camera, then that sets a
theoretical maximum of 12 stops of dynamic range, because the scale of f-stops
is also a 2x progression. However, note that at the dark end of the range, the
tonal separation is very coarse (whole stops only!) plus there will be noise
coming from the sensor anyway, so it would be more realistic to assume that
one or two bits get lost that way, and the real range would be nearer to 10
stops.

4) I think I understand the importance of linearity - kind-of-sort-of - from
printing.  Is this a similar concept? Ie evenly distributed tonal range?

[Mike] Hopefully Pieris's reply has helped you here.

5) At the end of the day we are severely constrained by the tonal range
capability of our printing.  Hogarth mentioned 8 stops for silver gelatin
paper.  How do I relate a linearised print of a step wedge on HPR with a paper
white dMin of .04 and a best black dMax of 1.68 to these figures?
(Wouldn't it be nice if they all used the same scale?)

[Mike] While echoing Pieris's comments, I'd add that for paper the same
relationship exist between dynamic range and density as it does for film (ref
my reply to point 2 above). Assume that the dMax and dMin are fixed for a
given type of paper, but you have several grades available. If you use a
harder grade, then a shorter range of values from the neg will map to that
range. If you use a softer paper, then more of the scale will fit. With
Photoshop we simply have much greater control over how we fit the values to
the available range, but in the end we are still limited by the output medium.

While the boundaries of the digital print are expanding, I guess we still need
to shoot by compressing the tonal range of the scene with ND filters (or
multiple exposures) so that it can be rendered well in the print - traditional
or inkjet.  I am trying to relate the two (and the steps that may be in
between eg scanning) so that when I get out my spot meter I am not only
thinking in terms of stops but also in terms of my printer's tonal range.
Sorry if these are basic questions but I think it will help a lot of people
tie all the talk of dMax back to the camera itself.

[Mike] Don't think in terms of your final print's tonal range, think in terms
of getting the best possible data in your capture. The principle is quite
similar to the approach you'd take using film, except you don't need to limit
yourself to only recording values on the neg that will be usefully printable.
Also, with neg film, you could theoretically use a really low-contrast
film/developer combination for absolutely everything you shoot, but then if
you decided you did want a nice contrasty print, you'd be trying to use very
hard paper to pull out tonal separations that are barely distinguishable on
the film. Therefore you might choose to develop for more contrast or use a
different film for a certain project. With digital the contrast ratio of the
sensor is fixed, so the best you can do is make sure you set the exposure so
that you use the full sensitivity that's available, and then use curves in
Photoshop to increase or reduce the contrast later. If you don't succeed in
using the full dynamic range (i.e., the histogram is bunched up down the
left-hand side) then if you choose to increase the shadow contrast you'll see
more noise than if you'd done a better job of the exposure.


<snip>

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Ok I am making my way through Norman's website - very heavy stuff but very
educational.  One question as I go:  what is the bit depth of the Canon 1Ds
MK II camera?  Can't seem to find this anywhere...

Hi Steve,

It's still 12-bit, just like the 1Ds, 1DII, 20D and for that matter even the
humble 300D/D-Rebel:

http://consumer.usa.canon.com/ir/controller?act=ModelTechSpecsAct&fcategoryid=139&modelid=10598

HTH

-= mike =-

-----Original Message-----
From: Steve Kale [mailto:stevekale@...] 
Sent: 24 November 2004 17:14
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Tonal range recording



Ok I am making my way through Norman's website - very heavy stuff but very
educational.  One question as I go:  what is the bit depth of the Canon 1Ds MK
II camera?  Can't seem to find this anywhere...




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misdirected, CSFB does not waive any confidentiality or privilege. CSFB
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==============================================================================

Thanks.  OK I think I am beginning to understand this stuff a lot more by
going through Noreman Koren's pages. I found "Why Gamma?" on this page to be
very helpful in relating film to photographic paper, and also for thinking
about the whole process of linearisation a print curve (printing a step
wedge, measuring it and linearising it).

http://www.normankoren.com/makingfineprints1A.html

My maths is very rusty though - I haven't done log math since highschool.
As a result I am stuck on the following sentence:

"One unit on a Log10 scale (such as Density) equals 3.32 exposure zones
(f-stops)."

Any help appreciated.

Steve

> From: "Nunan, Mike" <mike.nunan@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 24 Nov 2004 17:30:29 -0000
> To: "'DigitalBlackandWhiteThePrint@yahoogroups.com'"
> <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Tonal range recording
> 
> 
> Hi Steve,
> 
> It's still 12-bit, just like the 1Ds, 1DII, 20D and for that matter even the
> humble 300D/D-Rebel:
> 
> http://consumer.usa.canon.com/ir/controller?act=ModelTechSpecsAct&fcategoryid=
> 139&modelid=10598
> 
> HTH
>

Ok stet that.  F-stop = double the exposure/luminance. Duh.  Now I've got
it. So under current inks we are getting around 5.5 stops of tonal range
from matt papers.

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 24 Nov 2004 18:56:42 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range recording
> 
> 
> Thanks.  OK I think I am beginning to understand this stuff a lot more by
> going through Noreman Koren's pages. I found "Why Gamma?" on this page to be
> very helpful in relating film to photographic paper, and also for thinking
> about the whole process of linearisation a print curve (printing a step
> wedge, measuring it and linearising it).
> 
> http://www.normankoren.com/makingfineprints1A.html
> 
> My maths is very rusty though - I haven't done log math since highschool.
> As a result I am stuck on the following sentence:
> 
> "One unit on a Log10 scale (such as Density) equals 3.32 exposure zones
> (f-stops)."
> 
> Any help appreciated.
>

It seems that I've read that the "color" inks for the CMY positions 
are the same, only the chip differs between the different carts.  If 
so, shouldn't one be able to refill all color carts from the same 
bottle?  I know there are different part numbers for the bulk inks, 
but are they *really* different?

Paul?  Anyone?

Thanks,

Lee


-- 
Lee Hiers, AA4GA
Cornelia, Georgia

"Have Dobro Will Travel"

I'm told that they are NOT different inks. The bulk inks come in bottles 
marked for the C, M or Y position as you noted, but I'm using the same 
bottle of neutral ink to top up both the C and Y bottles in my CIS (I 
have warm ink in the M position) and have fine results doing so.

Cheers,
Kip

Lee Hiers wrote:

>It seems that I've read that the "color" inks for the CMY positions 
>are the same, only the chip differs between the different carts.  If 
>so, shouldn't one be able to refill all color carts from the same 
>bottle?  I know there are different part numbers for the bulk inks, 
>but are they *really* different?
>  
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Kip Babington 
<cbabing3@s...> wrote:
> I'm told that they are NOT different inks. The bulk inks come in bottles 
> marked for the C, M or Y position as you noted, but I'm using the same 
> bottle of neutral ink to top up both the C and Y bottles in my CIS (I 
> have warm ink in the M position) and have fine results doing so.
> 
> Cheers,
> Kip

Kip, I am going to buy the C86 in the next week of so.  And with the neutral ink in the 
C and Y positions and warm ink in the M position, what tone (near warm, neutral, or 
what) do you get with your ink set up?

Martin

The 1Ds is 12 bits. I think the 10/D20D are also 12 bits. Some medium format
digital backs are 14 bits, from what I hear. I'm sure this is accurate info
since I heard it on the web. ;-)

Steve

----- Original Message ----- 
From: "Steve Kale" <stevekale@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Wednesday, November 24, 2004 9:14 AM
Subject: Re: [Digital BW] Tonal range recording




Ok I am making my way through Norman's website - very heavy stuff but very
educational.  One question as I go:  what is the bit depth of the Canon 1Ds
MK II camera?  Can't seem to find this anywhere...





Please visit the Group Homepage to check the Files, and other resources as
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If you wish to receive no emails or just a daily digest, or you wish to
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Yep thanks - the PhaseOne digital backs are 16bits/12 f-stops of dynamic
range.

> From: steve_bye <steve_bye@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 24 Nov 2004 16:13:12 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range recording
> 
> 
> The 1Ds is 12 bits. I think the 10/D20D are also 12 bits. Some medium format
> digital backs are 14 bits, from what I hear. I'm sure this is accurate info
> since I heard it on the web. ;-)
> 
> Steve

Hmmm if 16 bit then why not 16 stops of dynamic range?

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 25 Nov 2004 00:27:33 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range recording
> 
> 
> Yep thanks - the PhaseOne digital backs are 16bits/12 f-stops of dynamic
> range.
> 
> 
>> From: steve_bye <steve_bye@...>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Wed, 24 Nov 2004 16:13:12 -0800
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: Re: [Digital BW] Tonal range recording
>> 
>> 
>> The 1Ds is 12 bits. I think the 10/D20D are also 12 bits. Some medium format
>> digital backs are 14 bits, from what I hear. I'm sure this is accurate info
>> since I heard it on the web. ;-)
>> 
>> Steve

> From: Steve Kale [mailto:stevekale@...]
>
> Hmmm if 16 bit then why not 16 stops of dynamic range?

Dynamic range is limited by noise. If you photograph a noiseless color, like
a white piece of paper out of focus, you'll probably find that the bottom
four bits are rubbish.

--

Ciao,               Paul D. DeRocco
Paul                mailto:pderocco@...

Martin -

The progression from pure neutral (neutral ink in C, M and Y positions) 
to pure warm starts with warm in the Y position, which gives a slight 
warming effect.  Warm in the M position (and neutral back in the Y 
position) is slightly warmer yet.  For me, this was warm enough and I 
didn't experiment further, but I assume that warm in the C position 
would be the next step.  I don't know how combinations would work out (M 
& Y, C & Y, M & C)  Paul Roark probably could tell us what the sequence is.

Remember that tone is quite paper dependent.  I was looking for a 
particular tone on Epson Enhanced Matte, and got it with warm in M.  My 
ink setup on Ilford Smooth Heavyweight Matte is cooler.  I think that on 
Legion Matte it is cooler still, but can't find the test prints to prove 
it at the moment.

What I did to check things out was to buy a set of both the neutral and 
warm inks, and play with combinations.  (The ink path in a C84 is very 
short, so you see the new ink after only about a page of printing 
following putting the new cartridge in.)  I "wasted" most of the warm 
set, because I didn't like the full warm effect, and so used very little 
of the C and only a bit more of the M before I decided I liked what I 
settled on and ordered a CIS.  Still, I have no doubts that what I have 
is the right choice, so for me it was money well spent.

Cheers,
Kip

mxgo95747 wrote:

>Kip, I am going to buy the C86 in the next week of so.  And with the neutral ink in the 
>C and Y positions and warm ink in the M position, what tone (near warm, neutral, or 
>what) do you get with your ink set up?
>
>Martin
>  
>

Bob 

Thanks for this - and to Steve and others who are helping me come up this
learning curve.  I have a couple of questions in response to your comments
below:


> From: "B. Campbell" <bellis60@...>

<snip>

> All traditional photographic papers have roughly the same contrast range, abut
> 1.8 - 2.1 (Ilfachrome had about the highest at 2.4).  The differences among
> them are in how that available range is apportioned among the shadows,
> midtones, and highlights, which is what a chracteristic curve will show you.

I now understand that the contrast ratio of a photographic paper is its
gamma - or put another way, gamma is contrast.  A paper could, therefore,
have a higher or lower dynamic range (reflection density range) and still
have the same contrast.

<snip>
 
> Density is measured in log units. .30 log units equals one stop.
>

Got it.

<snip>
 
> Hope this helps and that I'm not talking down to you..
> 

Certainly not!  I am sitting here with Normen Koren's website in front of me
and Ansel Adams' book The Print open to the discussion of the zone system on
my left and coming up a big learning curve!

A couple of additional points for me to check with you and others:

Ansel's zone system uses a 10 Zone range of which 8 are considered "dynamic
range".  Presumably this was a  useful number because for the printing
processes employed by him and others at the time, this range of mid exposure
+/- 4 stops suited the general dynamic range of the papers/chemicals used in
the printing process.  If papers had a broader more usable dynamic range he
might have gone to a, say, +/- 5 stops terminology and placed the mid point
at Zone VI.  Do I have this thinking correct?  If Ansel were stuck with the
dynamic range we can achieve from an inkjet printer on matt paper presumably
his zone system would have had just 5-6 zones?

Further, I understand his philosophy of making the best negative was driven
with the knowledge of his printing "restrictions" in hand and the knowledge
that he had a more limited (at least in comparison to digital manipulation)
opportunities to alter the tonal range significantly after the shutter had
been released.  (He did of course have access to negative processing
adjustments and different paper grades with different contrast ratios etc.)
But I think it is fair to say that he strived for the best negative with a
"down the middle of the fairway" print process in mind.

Digital (particularly when playing with 12 bits or more) provides us with a
great deal of latitude over tonal range post the shutter release - either by
manipulating the RAW data with a transformation/contrast curve or by
altering the data once it has been processed by the RAW converter with a
stock gamma and white point.  Some have mentioned that we need not be so
concerned any more with the restrictions of the print at the time of shutter
release because of this increased flexibility.  We can pick and choose later
which parts of the data we choose to reveal and which not. I understand
this.  

But are digital photographers really abandoning the sort of forward thinking
that Ansel has proposed?  Are people really saying capture the maximum tonal
range possible, conscious of the linearity of the sensor, by simply using
evaluative metering and dialling in exposure compensation such that the
histogram pushes as far to the right as possible without clipping? I guess a
proponent would argue that at least this method means we have the data
stored and as printing technology improves we can reprint the print and
present a better image with more of the available tonal range presented.
But don't you end up losing the benchmark of knowing at the time of shutter
release that you have defined the part of the scene that will print mid
grey?  Doesn't the final print then become simply a complete artistic
interpretation affected by memory and other factors? (Eg "I think I wanted
the door in my composition to be mid grey", or "I don't care what shade of
grey the door was - it looks better this way now.")  I am not saying this is
a bad thing just trying to determine what boundaries have been crossed.

I have not made it through all the materials you guys have given or pointed
me to and I will keep going but this lurks in the back of my mind as I go
through this.

Thanks again

Steve

Can I clarify some nits on this so that I have a clearer understanding?


> From: "Nunan, Mike" <mike.nunan@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 24 Nov 2004 12:26:55 -0000
> To: "'DigitalBlackandWhiteThePrint@yahoogroups.com'"
> <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Tonal range recording
> 
<snip>

> With digital the contrast ratio of the
> sensor is fixed, 

The gamma (contrast) of the sensor is not linear (or another way to put it,
the senor is linear) but we apply a contrast/gamma curve when converting
from RAW to RGB.  This curve need not be fixed.  Right?


> so the best you can do is make sure you set the exposure so
> that you use the full sensitivity that's available,

I am getting there on this but see my other post.

>and then use curves in
> Photoshop to increase or reduce the contrast later.

Or better yet use a better transformation curve in the RAW processing stage?

> If you don't succeed in
> using the full dynamic range (i.e., the histogram is bunched up down the
> left-hand side) then if you choose to increase the shadow contrast you'll see
> more noise than if you'd done a better job of the exposure.

Because noise is fixed and I have less observations to play with hence
signal to noise falls?  This is the bit I am currently chomping on with
rusty math!

Thanks

Steve

Steve,

You comments and questions below address the issues that I think need to be
addressed. The zone system was great for film, telling a photographer how to
control contrast using film development time and how to chose the exposure
to place the contrast range in the optimum place for recording optimum
tonality. Though we have bits and pieces of a digital replacement for the
zone system, it's not quite the same thing. "Exposing to the right" gets the
maximum info out of the sensor, but has the limitations you point of
disconnecting the capture from pre-visualizing the print. It seems to me we
need a contemporary Ansel Adams to bring clarity to digital exposure the way
Ansel did to film.

A first axiom might be to expose to the right BUT remember how much exposure
compensation was used so that it can be backed out when converting the raw
file to a psd/tiff. Backing out the compensation would put the blacks back
where they truly were, while maintaining the improved signal-to-noise ratio
gained by exposing to the right. The info needed to do this may already be
in the raw file as "exposure bias value," recorded in the EXIF data. By
undoing the compensation in the RAW converter using the exposure slider the
original contrast ratio would, I think, be maintained, but the exposure
would slide back to the left where it truly was.

It will be very interesting years from now to see which new insights proved
to be the critical new axioms of digital photography.

Steve Bye

----------------------
Meesage from Steve Kale:

Ansel's zone system uses a 10 Zone range of which 8 are considered "dynamic
range".  Presumably this was a  useful number because for the printing
processes employed by him and others at the time, this range of mid exposure
+/- 4 stops suited the general dynamic range of the papers/chemicals used in
the printing process.  If papers had a broader more usable dynamic range he
might have gone to a, say, +/- 5 stops terminology and placed the mid point
at Zone VI.  Do I have this thinking correct?  If Ansel were stuck with the
dynamic range we can achieve from an inkjet printer on matt paper presumably
his zone system would have had just 5-6 zones?

Further, I understand his philosophy of making the best negative was driven
with the knowledge of his printing "restrictions" in hand and the knowledge
that he had a more limited (at least in comparison to digital manipulation)
opportunities to alter the tonal range significantly after the shutter had
been released.  (He did of course have access to negative processing
adjustments and different paper grades with different contrast ratios etc.)
But I think it is fair to say that he strived for the best negative with a
"down the middle of the fairway" print process in mind.

Digital (particularly when playing with 12 bits or more) provides us with a
great deal of latitude over tonal range post the shutter release - either by
manipulating the RAW data with a transformation/contrast curve or by
altering the data once it has been processed by the RAW converter with a
stock gamma and white point.  Some have mentioned that we need not be so
concerned any more with the restrictions of the print at the time of shutter
release because of this increased flexibility.  We can pick and choose later
which parts of the data we choose to reveal and which not. I understand
this.

But are digital photographers really abandoning the sort of forward thinking
that Ansel has proposed?  Are people really saying capture the maximum tonal
range possible, conscious of the linearity of the sensor, by simply using
evaluative metering and dialling in exposure compensation such that the
histogram pushes as far to the right as possible without clipping? I guess a
proponent would argue that at least this method means we have the data
stored and as printing technology improves we can reprint the print and
present a better image with more of the available tonal range presented.
But don't you end up losing the benchmark of knowing at the time of shutter

release that you have defined the part of the scene that will print mid
grey?  Doesn't the final print then become simply a complete artistic
interpretation affected by memory and other factors? (Eg "I think I wanted
the door in my composition to be mid grey", or "I don't care what shade of
grey the door was - it looks better this way now.")  I am not saying this is
a bad thing just trying to determine what boundaries have been crossed.

I have not made it through all the materials you guys have given or pointed
me to and I will keep going but this lurks in the back of my mind as I go
through this.

Thanks again

Steve





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Hi Steve, 

Comments inline...

-----Original Message-----
From: Steve Kale
Sent: 25 November 2004 15:16
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Tonal range recording


Can I clarify some nits on this so that I have a clearer understanding?

[M] Sure!

<snip>

> With digital the contrast ratio of the sensor is fixed,

The gamma (contrast) of the sensor is not linear (or another way to put it,
the senor is linear) but we apply a contrast/gamma curve when converting from
RAW to RGB.  This curve need not be fixed.  Right?

[M] I think I see what you mean, but it's unconventional to talk about gamma
being linear when what you really mean is that there is a log curve involved
in the representation, so I'd avoid that. Look at it this way... Any image
file format represents pixel values in the form of numbers of some level of
precision. By saying that a given representation assumes some level of
"gamma", you are saying that the numbers must be interpreted on a log scale
rather than being directly proportional to the intensity. As long as you know
what the relationship is, you can get near-identical output on your monitor
from files that are encoded linear, in 2.2 gamma, or using any other value,
although some gamma values will make better use of the available numeric
precision than others. RAW files are very close to linear simply because of
the physical characteristics of the sensor. It would be possible to generate a
linear RGB TIFF from the RAW file but in practice this is done very rarely,
simply because the most commonly used colour spaces such as AdobeRGB and sRGB
are gamma 2.2 spaces.

> so the best you can do is make sure you set the exposure so that you 
> use the full sensitivity that's available,

I am getting there on this but see my other post.

>and then use curves in
> Photoshop to increase or reduce the contrast later.

Or better yet use a better transformation curve in the RAW processing stage?

[M] That would be better in the sense that it would provide slightly higher
precision. It might not be better in practical terms, because the curve
processing capabilities of the RAW converter are likely to be less flexible
and convenient than Photoshop's (you can't use masking to restrict changes to
part of the image, for example) and if there are any operations that you
wished to do before the curve manipulations, you'd be stuck. If you've chosen
a 2.2 gamma space as the target for your RAW conversion, the benefits of the
slightly improved numerical accuracy would be marginal anyway even in 8-bit,
and probably near-to-nonexistant in 16-bit.

If you really wanted to be obsessive about it, you could convert the RAW file
to linear 16-bit RGB, work on that in PS and then as a final step use Convert
to Profile with AdobeRGB as the destination space. That ought to retain the
highest possible precision, but my own experiments with linear RGB files in PS
have taught me that the display output routines are not really designed for
this and you get some unwelcome effects on the monitor. I have a strong
suspicion that the whole display output piece of PS is 8-bit, so your
beautifully precise 16-bit linear file values get chopped to 8 bits *before*
being fed into the conversion, leading to very ugly shadow rendering on the
display.

> If you don't succeed in
> using the full dynamic range (i.e., the histogram is bunched up down 
> the left-hand side) then if you choose to increase the shadow contrast 
> you'll see more noise than if you'd done a better job of the exposure.

Because noise is fixed and I have less observations to play with hence signal
to noise falls?  This is the bit I am currently chomping on with rusty math!

[M] Yeah, that's it in a nutshell. Think you're definitely getting there.

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How do I relate and convert a measured paper/ink density value back to the
0-255 scale used in PS's curves?

If I were to print a 255 step wedge out for a particular printer/paper/ink
setup I will have in front of me the tonal range (in 8 bits) of that setup.
The 0% wedge with a density of say 0.04 is off-white rather than pure white
and the 100% wedge (or 255 wedge) is also a dark dark grey rather than pure
black - let's give it a density of 1.65.  I have a compressed tonal range
versus the input values of the image on the display (with a good monitor
with great tonal range).

Furthermore, if I understand the process of printer linearization properly,
my "output space" is linearized and so there is a straight line relationship
between steps in input values and the steps in output values.  And so if the
printer is linearized properly this compression of tonal range can be
"replicated" by a curve which has the zero output level shifted up and the
255 output level lowered.  The slope of the curve is less and hence the
contrast or gamma has been lowered.  Worse yet, if, as is most commonly the
case, there is greater tonal compression at the 255 level than at the 0
level, ie we have better paper whites than we can achieve ink blacks, then
the mid-gray value has shifted lower also.  These two factors, I understand,
are why unadjusted prints print "lighter than they appear on screen" - a
common complaint.  

If I can relate my printer (paper and ink) output range, dmin and dmax, to
the 0-255 range in PS's curves then I have a more precise mechanism for
dealing with output tonal range compression and readjusting the mid grey
point (and any other points on either side of it) - I can use a curve to
compress the tonal range before it gets to the printer with much greater
control over how that compression is done (or in other words I can get away
from linearized situation that exists in the printer domain).

Thoughts?

Steve,

I have some test strips at http://home1.gte.net/res09aij/Test-files.htm that
show some relationships I find helpful.  This is just my approach, however.
I've never seen a real scientific discussion of the theoretically "correct"
way to "linearize" a gray scale.  Just what the midtone density should be is
not 100% clear to me.  

However, you noted the range of 0.04 for the paper white to 1.65 for the
100% black.  That just happens to be a typical EEM range.  So, reading a
0.04 EEM paper white I get a Lab L reading of 97.  Taking a reading of the
1.65 black with my X-Rite, I get L = 16.7.  The committee that made the Lab
scale did a tremendous amount of work on how we see.  So, I take their scale
as rather persuasive.  So, if you average the EEM black and white Lab
Luminosity values you get about L = 56.9.  You'll see on my test strips that
I put 50% at 0.61 visual density.  This is about Lab L=56.9.  (I use the
readouts of the X-Rite for these equivalents.  I think there is a formula,
but I don't have it.)

Perhaps not by coincidence, this was also about the average PiezoBW 50% I
measured some years ago when I was still printing with that system, and I
wanted my files to be able to print on either system.

When I profile other papers with a higher dmax, I don't change the 50% spot,
because I think (perhaps incorrectly) that the midtone density is what most
people see.  That seems to determine how bright or dark the overall image
is.  A great black and bright white just give more dynamic range.  Our
ability to see into those 2+ black densities, however, is limited.  So, I
use 0.61 for my target 50% density for all papers.

On the other hand, the Kodak standard gray card is L = 50.  I think one
could also argue that we ought to standardize on that as a uniform 50%
density no matter what the paper white and ink black happen to be.  If I
were starting from scratch, I'd be tempted to do just that.  I think using
the L=50 midpoint might make the average monitor closer to the print.  L=50
is about density 0.74 on my X-Rite system.

I'm not sure this is what you were looking for, but this is what I do.

Paul
www.PaulRoark.com

__________________________________

-----Original Message-----
From: Steve Kale [mailto:stevekale@...] 
Sent: Tuesday, November 30, 2004 5:26 PM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Tonal range and linearization



How do I relate and convert a measured paper/ink density value back to the
0-255 scale used in PS's curves?

If I were to print a 255 step wedge out for a particular printer/paper/ink
setup I will have in front of me the tonal range (in 8 bits) of that setup.
The 0% wedge with a density of say 0.04 is off-white rather than pure white
and the 100% wedge (or 255 wedge) is also a dark dark grey rather than pure
black - let's give it a density of 1.65.  I have a compressed tonal range
versus the input values of the image on the display (with a good monitor
with great tonal range).

Furthermore, if I understand the process of printer linearization properly,
my "output space" is linearized and so there is a straight line relationship
between steps in input values and the steps in output values.  And so if the
printer is linearized properly this compression of tonal range can be
"replicated" by a curve which has the zero output level shifted up and the
255 output level lowered.  The slope of the curve is less and hence the
contrast or gamma has been lowered.  Worse yet, if, as is most commonly the
case, there is greater tonal compression at the 255 level than at the 0
level, ie we have better paper whites than we can achieve ink blacks, then
the mid-gray value has shifted lower also.  These two factors, I understand,
are why unadjusted prints print "lighter than they appear on screen" - a
common complaint.  

If I can relate my printer (paper and ink) output range, dmin and dmax, to
the 0-255 range in PS's curves then I have a more precise mechanism for
dealing with output tonal range compression and readjusting the mid grey
point (and any other points on either side of it) - I can use a curve to
compress the tonal range before it gets to the printer with much greater
control over how that compression is done (or in other words I can get away
from linearized situation that exists in the printer domain).

Thoughts?






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OK so let me first of all say that you guys know a LOT more about this than
me and that I am simply fumbling around in the dark trying to learn about
luminance and illuminance (excuse the pun) with a very dodgy recollection of
logarithmic mathematics. So forgive me if I don't use the right terminology,
if I am overly exhaustive in outlining my thoughts or if I tangle myself up
in logic knots here.

In short, Paul, I think you are one step ahead of me here in your answer and
that what you are doing is a defined mixture of the two step process I saw
happening - bear with me.

I understand that there is a direct relationship between luminance (display)
and illuminance (prints).  Gamma (contrast) defines the rate of change of
luminance (or illuminance) as we move from normalised pixel values of 0 to
1.  That is, in a simplified form, luminance = (normalised pixel
value)^gamma.  So even if a printer (and paper and ink combination) were
capable of the same tonal range as a display, unless it used the same gamma
setting the prints would look very different from the screen.  In other
words, because we work in a non-coloursynced workflow world (where
differences in gamma would be adjusted for) we must ensure that any printer
linearisation (the process of ensuring that the log of each side of this
equation is a straight line) uses the same gamma as our display. As soon as
we have a different gamma we depart dramatically from "what you see is what
you get".

Now our printers are not capable of the same tonal range as our monitors.
We don't get a bright white and we don't get dark blacks.  Even so, ideally,
we would still have a printer setup that faithfully portrays the various
in-range luminances that we see on screen - that is, the in-range tonal
range would be reproduced with the SAME gamma and mid point.  If not then we
morph the entire image and begin to lose precise control of dealing with
"out-of-gamut" shades.  Out of range pixel values (highlights and,
particularly, deep blacks) can't be reproduced by the printer.  In this
scenario, the out of range blacks would simply be reproduced as black as
possible.  This compression can be simulated in PS with a curve whereby the
end points on the input scale are clipped to constant output points (using
the 0-100% scale, lift the highlight point up then right and the black point
down then left, in each case keeping the input equal to output).  Note the
overall image is not radically changed, gamma is the same (the slope of the
PS curve has not changed), except at the two ends of the spectrum (where
clipping occurs). 

This clipping is not generally satisfactory and we would normally be
prepared to make controlled adjustments to the IMAGE in order that we get
good relative tonal display in the displayed or printed image.  We would
most likely take this hard edged inverted Z curve and smooth it to a nice S
curve around the same mid.  We can decide over what range we are prepared to
accommodate tonal changes to "open-up" the shadows and highlights (limiting
the range, say, by anchoring the 25/25 and 75/75 points for example).

If I can define (and I must be able to) where my printer tonal range starts
and stops in the little output gray scale in PS's curves function then I
have precise control over how the image tonal range is compressed into the
printer tonal range.

What I am not sure about is how programmes like QTR really do their
linearization.  I suspect, though, that they linearize such that rate of
change in -log(luminance) [guess I should have the negative because a print
is illuminated rather luminates] for a change in log(normalised pixel value)
is constant from dmin to dmax.  In other words, gamma is different from the
display gamma.  Because the tonal range is compressed this gamma is by
definition lower than display gamma and most likely the mid-grey point has
shifted. (Here is where I admit fully I need input from people like Roy.)

Paul, I think what you do is in effect a hybrid approach whereby you are in
effect creating the S curve and defining placement of the mid point in one
go.  Does this make sense?  I am not sure where the 50% point should be
EXCEPT to say that it should be the same as the display or workspace.

I would advocate, I think (!), a more rigorous two-step process.  (A) Define
the two end points of our printer's tonal range and ensure that the image's
tonal range is compressed with a PS curve (of whatever shape a person may
desire) before the image is sent to the printer.  (B) Calibrate or linearize
the printer such that it faithfully reproduces its tonal range with the same
gamma as our display gamma.

Even if the second part is done automatically I need to know what my two
tonal range end points are in terms of the 0-255 scale - or perhaps more
easily the 0-100% scale - used by PS in its curves function in order to
accurately compress the image tonal range to the printer tonal range before
sending it to print.  There must be a mathematical relationship here.  Take
an input pixel of 85% for example.  Dark grey.  Annoyingly PS has this
around the other way to normalised pixel values. Luminance = (normalised
pixel value)^2.2 = 0.15^2.2 = 0.0154. Density = -log10(luminance). So this
equates to a density of 1.81. Is my maths right?  Of course we can go in
reverse, beginning with our density readings from our linearized step
wedges.  

Have I almost answered my own question?  My mathematics is rusty!!! If I
know the density value then what is the formula for deriving luminance and
then getting back to a normalised pixel value which I can then reinterpret
into PS's 0-100% (or 0-255) curves scale?

(A dMax of 1.65 (EEM) equates to a normalised pixel value of around 0.175 (I
am simply guessing numbers here because I can't do the maths above!) which
is equal to 82.5% on PS's 0-100% scale.  So the max output I can have is
82%.  Let's assume the min input I can have is 5%.  It is not coincidental
that if you do this straight line "curve" and toggle it on and off and
compare it to toggling a soft proof of QTR's EEM curve that you see similar
tonal range adjustments.  I suspect that most of us are really interested in
soft-proofing not for proofing the change in hue (is this the right term?
tint) but for previewing relative and absolute tonal range.)

So I would be grateful if someone could help me with my maths problem and
also for input on the printer gamma point.

Cheers

Steve

> From: Paul Roark <paul.roark@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 30 Nov 2004 18:19:11 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Tonal range and linearization
> 
> 
> Steve,
> 
> I have some test strips at http://home1.gte.net/res09aij/Test-files.htm that
> show some relationships I find helpful.  This is just my approach, however.
> I've never seen a real scientific discussion of the theoretically "correct"
> way to "linearize" a gray scale.  Just what the midtone density should be is
> not 100% clear to me.
> 
> However, you noted the range of 0.04 for the paper white to 1.65 for the
> 100% black.  That just happens to be a typical EEM range.  So, reading a
> 0.04 EEM paper white I get a Lab L reading of 97.  Taking a reading of the
> 1.65 black with my X-Rite, I get L = 16.7.  The committee that made the Lab
> scale did a tremendous amount of work on how we see.  So, I take their scale
> as rather persuasive.  So, if you average the EEM black and white Lab
> Luminosity values you get about L = 56.9.  You'll see on my test strips that
> I put 50% at 0.61 visual density.  This is about Lab L=56.9.  (I use the
> readouts of the X-Rite for these equivalents.  I think there is a formula,
> but I don't have it.)
> 
> Perhaps not by coincidence, this was also about the average PiezoBW 50% I
> measured some years ago when I was still printing with that system, and I
> wanted my files to be able to print on either system.
> 
> When I profile other papers with a higher dmax, I don't change the 50% spot,
> because I think (perhaps incorrectly) that the midtone density is what most
> people see.  That seems to determine how bright or dark the overall image
> is.  A great black and bright white just give more dynamic range.  Our
> ability to see into those 2+ black densities, however, is limited.  So, I
> use 0.61 for my target 50% density for all papers.
> 
> On the other hand, the Kodak standard gray card is L = 50.  I think one
> could also argue that we ought to standardize on that as a uniform 50%
> density no matter what the paper white and ink black happen to be.  If I
> were starting from scratch, I'd be tempted to do just that.  I think using
> the L=50 midpoint might make the average monitor closer to the print.  L=50
> is about density 0.74 on my X-Rite system.
> 
> I'm not sure this is what you were looking for, but this is what I do.
> 
> Paul
> www.PaulRoark.com

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale 
<stevekale@b...> wrote:

> So I would be grateful if someone could help me with my maths 
problem and
> also for input on the printer gamma point.
> 
> Cheers
> 


Hi Steve,

If you haven't done so already, check out Bruce Lindbloom's site 
(http://www.brucelindbloom.com). He has many helpful conversion 
calculators, equations, and information about color and perception 
theory.

Regards,
Peter.

Hi Peter

This is much simpler than anything on Bruce's site.

I do know that in its simplified form:

Luminance = (normalised pixel value)^gamma

And that:

Density = -log10(luminance)

So if gamma =2.2

Density = -log10(normalised pixel value^2.2)

Which means:

(Normalised pixel value)^2.2 = 10^(-Density)

And here is where my knowledge of algebra leaves me wanting.  [if my gamma
were simply 2 then I know I could take the square root of both sides and be
done]

If I know a density value, eg 1.65, then

(normalised pixel value)^2.2 = 10^-1.65 = 0.02239

I am having trouble with the very last step in this simple algebra.

By the very unsatisfactory method of interpolation I know the answer is
normalised pixel value is approx 0.1775.  In other words, a density of 1.65
- about the max we can get from EEM - is roughly equivalent to a 82.25%
black in a 2.2 gamma space.  Any black darker than this can not be
reproduced on the printer.  So if you were to look at your nicely stretched
image's histogram in PS, you would know that the left-most 17.75% (or you
prefer to think in an 8 bit 0-255 range... all values from 0 to 45) could
never be printed as you are looking at it!  All those pixel values are
simply outside the tonal range of the printer.  A similar calculation can be
done for the highlights.

Cheers

Steve

> From: Peter <spamme2001@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 02 Dec 2004 02:10:58 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
> <stevekale@b...> wrote:
> 
>> So I would be grateful if someone could help me with my maths
> problem and
>> also for input on the printer gamma point.
>> 
>> Cheers
>> 
> 
> 
> Hi Steve,
> 
> If you haven't done so already, check out Bruce Lindbloom's site
> (http://www.brucelindbloom.com). He has many helpful conversion
> calculators, equations, and information about color and perception
> theory.
> 
> Regards,
> Peter.
>

OK got it (on the subway my maths lessons finally came back).

Normalised pixel value = ((10^(-Density))^(1/Gamma)

So if we know the dMin and dMax of our printer/ink/paper combination (by
measuring the density values of paper white and max ink load, respectively)
we can identify, in either terms of normalised pixel values or in an 8 bit
0-255 range (or any other bit rate), how much of the tonal range can be
rendered by the printer.

For EEM which I will say has a density range of 0.043 to 1.65, this range is
approximately, using the 0-255 scale, pixels from 18 to 243, assuming a
gamma of 2.2.  Anything outside this range can't be reproduced on EEM with
today's inks because we can't get the ink black enough and the paper isn't
white enough.  

So what?

Well the problem is we are taught to stretch our scan or initial digital
capture to fill the full tonal range from 0-255.  What we don't do, however,
is compress it back again to the tonal range of our printer before sending
it to print.  

But it still prints fine!

Well yes but this is because a programme like QTR (I am using QTR as the
example here only because it is transparent and simply the one I most
familiar with) has its own set of tables which tell the printer how much of
what ink to put down on paper for a given pixel value and such tables range
from 0-255.  But let's look at the end points of this table.  For example,
in a simple one ink curve file, the 100% black or 0 pixel value point is
defined by Limit_K = x where x is a percentage (assuming no use of BOOST).
If x is set to 95% then the quad file will have 0.95x2^16 = 62,259.  Note
this is the value at pixel value = 0.  Yet from above we know that a pixel
of value 18 (not 0) should be getting this amount of ink! In the table for
this ink curve the value and hence the ink ascribed to a pixel of value 18
is LESS THAN the ink it should get to be effectively portrayed as shown on
screen.

In other words, linearised or not, the printer space has a GAMMA that bears
little resemblance to the one we are using for a workspace.  It is no wonder
that the printer prints images lighter than they appear on screen - remember
all our pixels with value 18 are getting less ink than the should, and so on
and so forth.  Because we are not working in a colour synchronised world
where differences in gamma are managed and there are complicated mechanisms
for dealing with out of gamut colours we will never get a WYSIWYG workflow
if the printer space/gamma differs markedly from the workspace/gamma.

Consequently we are left fiddling with s-curves to try to get the print to
match to some extent what we see on screen.  Worse yet this fiddling is very
imprecise because it is not done with an understanding of the tonal range
the the printer is capable of and not done with an understanding of the
printer's gamma.  

Until we have a workflow in which the printer's gamma is aligned with that
of our workspace and we send an image that is within the tonal range of the
printer you will get a WYSIWYG workflow.  But it is possible to better align
the two - after all we know the characteristics of our workspace and we know
the normalised pixel values that can be reproduced by the printer/paper/ink
combination.  

If, in my example, QTR put the value 62,259 in the 18 slot and 0 in the 243
slot and linearised all points in between to our workspace gamma of 2.2, and
we compressed with a PS curve the tonal range of the image to a range of 18
to 243 then we should get a WYSIWYG result.  The PS curve is easier and more
intuitive to do - we have the end points defined for us and can think about
whether the mid point should be altered or not (followers of Mr Adam's Zone
System would make sure it was put back to 128/128 because they placed it
there at the rime of shooting).

So - any takers?

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 02 Dec 2004 11:10:04 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Hi Peter
> 
> This is much simpler than anything on Bruce's site.
> 
> I do know that in its simplified form:
> 
> Luminance = (normalised pixel value)^gamma
> 
> And that:
> 
> Density = -log10(luminance)
> 
> So if gamma =2.2
> 
> Density = -log10(normalised pixel value^2.2)
> 
> Which means:
> 
> (Normalised pixel value)^2.2 = 10^(-Density)
> 
> And here is where my knowledge of algebra leaves me wanting.  [if my gamma
> were simply 2 then I know I could take the square root of both sides and be
> done]
> 
> If I know a density value, eg 1.65, then
> 
> (normalised pixel value)^2.2 = 10^-1.65 = 0.02239
> 
> I am having trouble with the very last step in this simple algebra.
> 
> By the very unsatisfactory method of interpolation I know the answer is
> normalised pixel value is approx 0.1775.  In other words, a density of 1.65
> - about the max we can get from EEM - is roughly equivalent to a 82.25%
> black in a 2.2 gamma space.  Any black darker than this can not be
> reproduced on the printer.  So if you were to look at your nicely stretched
> image's histogram in PS, you would know that the left-most 17.75% (or you
> prefer to think in an 8 bit 0-255 range... all values from 0 to 45) could
> never be printed as you are looking at it!  All those pixel values are
> simply outside the tonal range of the printer.  A similar calculation can be
> done for the highlights.
> 
> Cheers
> 
> Steve
> 
> 
>> From: Peter <spamme2001@...>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Thu, 02 Dec 2004 02:10:58 -0000
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: Re: [Digital BW] Tonal range and linearization
>> 
>> 
>> 
>> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
>> <stevekale@b...> wrote:
>> 
>>> So I would be grateful if someone could help me with my maths
>> problem and
>>> also for input on the printer gamma point.
>>> 
>>> Cheers
>>> 
>> 
>> 
>> Hi Steve,
>> 
>> If you haven't done so already, check out Bruce Lindbloom's site
>> (http://www.brucelindbloom.com). He has many helpful conversion
>> calculators, equations, and information about color and perception
>> theory.
>> 
>> Regards,
>> Peter.
>> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See „Group Topic, Rules and Guidelines‰ in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE „OWNER‰ AND
> „MODERATORS‰ OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  „OWNER‰ AND „MODERATORS‰ OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Sorry my 18 should be 0.1778x255 = 45.  When moving to using the 0-255 scale
I forgot to adjust the 17.8% to the new scale.

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 02 Dec 2004 15:21:34 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> OK got it (on the subway my maths lessons finally came back).
> 
> Normalised pixel value = ((10^(-Density))^(1/Gamma)
> 
> So if we know the dMin and dMax of our printer/ink/paper combination (by
> measuring the density values of paper white and max ink load, respectively)
> we can identify, in either terms of normalised pixel values or in an 8 bit
> 0-255 range (or any other bit rate), how much of the tonal range can be
> rendered by the printer.
> 
> For EEM which I will say has a density range of 0.043 to 1.65, this range is
> approximately, using the 0-255 scale, pixels from 18 to 243, assuming a
> gamma of 2.2.  Anything outside this range can't be reproduced on EEM with
> today's inks because we can't get the ink black enough and the paper isn't
> white enough.  
> 
> So what?
> 
> Well the problem is we are taught to stretch our scan or initial digital
> capture to fill the full tonal range from 0-255.  What we don't do, however,
> is compress it back again to the tonal range of our printer before sending
> it to print.  
> 
> But it still prints fine!
> 
> Well yes but this is because a programme like QTR (I am using QTR as the
> example here only because it is transparent and simply the one I most
> familiar with) has its own set of tables which tell the printer how much of
> what ink to put down on paper for a given pixel value and such tables range
> from 0-255.  But let's look at the end points of this table.  For example,
> in a simple one ink curve file, the 100% black or 0 pixel value point is
> defined by Limit_K = x where x is a percentage (assuming no use of BOOST).
> If x is set to 95% then the quad file will have 0.95x2^16 = 62,259.  Note
> this is the value at pixel value = 0.  Yet from above we know that a pixel
> of value 18 (not 0) should be getting this amount of ink! In the table for
> this ink curve the value and hence the ink ascribed to a pixel of value 18
> is LESS THAN the ink it should get to be effectively portrayed as shown on
> screen.
> 
> In other words, linearised or not, the printer space has a GAMMA that bears
> little resemblance to the one we are using for a workspace.  It is no wonder
> that the printer prints images lighter than they appear on screen - remember
> all our pixels with value 18 are getting less ink than the should, and so on
> and so forth.  Because we are not working in a colour synchronised world
> where differences in gamma are managed and there are complicated mechanisms
> for dealing with out of gamut colours we will never get a WYSIWYG workflow
> if the printer space/gamma differs markedly from the workspace/gamma.
> 
> Consequently we are left fiddling with s-curves to try to get the print to
> match to some extent what we see on screen.  Worse yet this fiddling is very
> imprecise because it is not done with an understanding of the tonal range
> the the printer is capable of and not done with an understanding of the
> printer's gamma. 
> 
> Until we have a workflow in which the printer's gamma is aligned with that
> of our workspace and we send an image that is within the tonal range of the
> printer you will get a WYSIWYG workflow.  But it is possible to better align
> the two - after all we know the characteristics of our workspace and we know
> the normalised pixel values that can be reproduced by the printer/paper/ink
> combination.  
> 
> If, in my example, QTR put the value 62,259 in the 18 slot and 0 in the 243
> slot and linearised all points in between to our workspace gamma of 2.2, and
> we compressed with a PS curve the tonal range of the image to a range of 18
> to 243 then we should get a WYSIWYG result.  The PS curve is easier and more
> intuitive to do - we have the end points defined for us and can think about
> whether the mid point should be altered or not (followers of Mr Adam's Zone
> System would make sure it was put back to 128/128 because they placed it
> there at the rime of shooting).
> 
> So - any takers?
> 
> 
> 
>> From: Steve Kale <stevekale@...>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Thu, 02 Dec 2004 11:10:04 +0000
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: Re: [Digital BW] Tonal range and linearization
>> 
>> 
>> Hi Peter
>> 
>> This is much simpler than anything on Bruce's site.
>> 
>> I do know that in its simplified form:
>> 
>> Luminance = (normalised pixel value)^gamma
>> 
>> And that:
>> 
>> Density = -log10(luminance)
>> 
>> So if gamma =2.2
>> 
>> Density = -log10(normalised pixel value^2.2)
>> 
>> Which means:
>> 
>> (Normalised pixel value)^2.2 = 10^(-Density)
>> 
>> And here is where my knowledge of algebra leaves me wanting.  [if my gamma
>> were simply 2 then I know I could take the square root of both sides and be
>> done]
>> 
>> If I know a density value, eg 1.65, then
>> 
>> (normalised pixel value)^2.2 = 10^-1.65 = 0.02239
>> 
>> I am having trouble with the very last step in this simple algebra.
>> 
>> By the very unsatisfactory method of interpolation I know the answer is
>> normalised pixel value is approx 0.1775.  In other words, a density of 1.65
>> - about the max we can get from EEM - is roughly equivalent to a 82.25%
>> black in a 2.2 gamma space.  Any black darker than this can not be
>> reproduced on the printer.  So if you were to look at your nicely stretched
>> image's histogram in PS, you would know that the left-most 17.75% (or you
>> prefer to think in an 8 bit 0-255 range... all values from 0 to 45) could
>> never be printed as you are looking at it!  All those pixel values are
>> simply outside the tonal range of the printer.  A similar calculation can be
>> done for the highlights.
>> 
>> Cheers
>> 
>> Steve
>> 
>> 
>>> From: Peter <spamme2001@...>
>>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>>> Date: Thu, 02 Dec 2004 02:10:58 -0000
>>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>>> Subject: Re: [Digital BW] Tonal range and linearization
>>> 
>>> 
>>> 
>>> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
>>> <stevekale@b...> wrote:
>>> 
>>>> So I would be grateful if someone could help me with my maths
>>> problem and
>>>> also for input on the printer gamma point.
>>>> 
>>>> Cheers
>>>> 
>>> 
>>> 
>>> Hi Steve,
>>> 
>>> If you haven't done so already, check out Bruce Lindbloom's site
>>> (http://www.brucelindbloom.com). He has many helpful conversion
>>> calculators, equations, and information about color and perception
>>> theory.
>>> 
>>> Regards,
>>> Peter.
>>> 
>> 
>> 
>> 
>> 
>> 
>> Please visit the Group Homepage to check the Files, and other resources as
>> they are often being updated.
>> 
>> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>> 
>> If you wish to receive no emails or just a daily digest, or you wish to
>> unsubscribe, please edit your Membership preferences by visiting this same
>> page.
>> 
>> Please follow these basic guidelines:
>> - As threads develop, trim off excess portions of earlier messages to keep
>> them short.
>> - Good manners are required at all time. No personal attacks or flames.
>> Hostile, aggressive or argumentative users may be removed from the membership
>> without notice.
>> - Keep your posts and threads related to the group topic of digital B&W
>> printing. Users who persistently make off-topic posts may be removed from the
>> membership.
>> - By posting on this forum you agree to abide by the group rules and
>> guidelines, and to abide by the actions and decisions of the group Owner and
>> Moderators. See „Group Topic, Rules and Guidelines‰ in the Files section:
>> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
>> 
>> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
>> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE „OWNER‰ AND
>> „MODERATORS‰ OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
>> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
>> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
>> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  „OWNER‰ AND „MODERATORS‰
>> OF
>> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF
>> SUCH
>> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
>> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
>> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
>> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
>> DIGITAL BW, THE PRINT YAHOO GROUP.
>>  
>> Yahoo! Groups Links
>> 
>> 
>> 
>>  
>> 
>> 
>> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
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> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
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> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See �Group Topic, Rules and Guidelines� in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE �OWNER� AND
> �MODERATORS� OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  �OWNER� AND �MODERATORS� OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:

snip...

> For EEM which I will say has a density range of 0.043 to 1.65, this
range is
> approximately, using the 0-255 scale, pixels from 18 to 243, assuming a
> gamma of 2.2.  Anything outside this range can't be reproduced...


Steve, perhaps you correct yourself later in the post (sorry, out of
time) but this is incorrect.
The entire path from numbers exiting Photoshop to ink hitting paper
does not clip as you suggest.

255 winds up mapping to your 0.043 paper, and 0 to your 1.65 ink
black. All in between is "compressed" accordingly. If you have
clipping such as you imply, there are other problems. The nature of
the compression is determined by your entire workflow and device
characteristics.

Tyler
www.custom-digital.com

Yes what you say is correct.  As set up at the moment, a 255 pixel (or
normalised pixel value of 1) goes to paper white 0.043 and 0 pixel to 1.65.
But note that the gamma of such a range is completely different from the
workspace gamma.  In the workspace gamma we go from density values of 0.043
to 1.65 in pixel values of 243 to 45.  This is my point.  As a result, we
work in a tonal range of 0-255 with a gamma of 2.2 yet print with a device
which has a tonal range of 45-243 and a gamma of lord knows what....No
wonder we don't get a WYSIWYG output.  Better to deliver the printer a tonal
range it can handle (43-293) and have it calibrated to the same gamma as our
workspace. No?

> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 02 Dec 2004 16:20:01 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
> <stevekale@b...> wrote:
> 
> snip...
> 
>> For EEM which I will say has a density range of 0.043 to 1.65, this
> range is
>> approximately, using the 0-255 scale, pixels from 18 to 243, assuming a
>> gamma of 2.2.  Anything outside this range can't be reproduced...
> 
> 
> Steve, perhaps you correct yourself later in the post (sorry, out of
> time) but this is incorrect.
> The entire path from numbers exiting Photoshop to ink hitting paper
> does not clip as you suggest.
> 
> 255 winds up mapping to your 0.043 paper, and 0 to your 1.65 ink
> black. All in between is "compressed" accordingly. If you have
> clipping such as you imply, there are other problems. The nature of
> the compression is determined by your entire workflow and device
> characteristics.
> 
> Tyler
> www.custom-digital.com
> 
> 
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See ³Group Topic, Rules and Guidelines² in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE ³OWNER² AND
> ³MODERATORS² OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  ³OWNER² AND ³MODERATORS² OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Arghh!! I meant:


Better to deliver the printer a tonal range it can handle (45-243).....

> From: Steve Kale <stevekale@...>
> Date: Thu, 02 Dec 2004 16:42:47 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> Yes what you say is correct.  As set up at the moment, a 255 pixel (or
> normalised pixel value of 1) goes to paper white 0.043 and 0 pixel to 1.65.
> But note that the gamma of such a range is completely different from the
> workspace gamma.  In the workspace gamma we go from density values of 0.043 to
> 1.65 in pixel values of 243 to 45.  This is my point.  As a result, we work in
> a tonal range of 0-255 with a gamma of 2.2 yet print with a device which has a
> tonal range of 45-243 and a gamma of lord knows what....No wonder we don't get
> a WYSIWYG output.  Better to deliver the printer a tonal range it can handle
> (43-293) and have it calibrated to the same gamma as our workspace. No?
> 
> 
>> From: Tyler Boley <tyler@...>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Thu, 02 Dec 2004 16:20:01 -0000
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: Re: [Digital BW] Tonal range and linearization
>> 
>> 
>> 
>> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
>> <stevekale@b...> wrote:
>> 
>> snip...
>> 
>>> For EEM which I will say has a density range of 0.043 to 1.65, this
>> range is
>>> approximately, using the 0-255 scale, pixels from 18 to 243, assuming a
>>> gamma of 2.2.  Anything outside this range can't be reproduced...
>> 
>> 
>> Steve, perhaps you correct yourself later in the post (sorry, out of
>> time) but this is incorrect.
>> The entire path from numbers exiting Photoshop to ink hitting paper
>> does not clip as you suggest.
>> 
>> 255 winds up mapping to your 0.043 paper, and 0 to your 1.65 ink
>> black. All in between is "compressed" accordingly. If you have
>> clipping such as you imply, there are other problems. The nature of
>> the compression is determined by your entire workflow and device
>> characteristics.
>> 
>> Tyler
>> www.custom-digital.com
>>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> Yes what you say is correct.  As set up at the moment, a 255 pixel (or
> normalised pixel value of 1) goes to paper white 0.043 and 0 pixel
to 1.65.
> But note that the gamma of such a range is completely different from the
> workspace gamma.

The gamma, on final paper, is determined by workflow. And in fact, the
working space and results on paper can be made to match quite well,
but a short novel could be written on the many ways to do so.

>...Better to deliver the printer a tonal
> range it can handle (43-293)...
> Better to deliver the printer a tonal range it can handle (45-243).....
> and have it calibrated to the same gamma as our
> workspace. No?

No, that will result in even further compression. 243 will map to a
light gray instead of paper white, 45 will map to less than ink black,
lowering your potential final density range.

Tyler
www.custom-digital.com

Yes if all you did was do a PS curve compressing the image tonal range to
45-243 then you would end up with an even flatter image.  This is because
you have compressed the image tonal range and done nothing with the printer
gamma.  But if instead I set up the printer such that a pixel value of 45 is
delivered a full ink load, a pixel value of 243 is given paper white, and
the points in between have the same gamma as the workspace then you will get
WYSISYG. In this case, I have equated the two environments (manually because
I don't have colorsync - we are using Same as Source, a non-colour managed
workflow).

The "WYSIWY don't G" problem is because the printer gamma (that which
defines the rate of change of density produced from pixel value 0 to value
255) is completely different from that of the workspace. The printer goes
from 0.043 (@ 255) to 1.65 (@ 0).  The display (and underlying image values)
goes from 0 (the calibrated white point, D50) to a maximum black way beyond
1.65 in the same 8bit 0-255 range.

(You might then ask what would the printer do upon receiving pixel values
less than 45 and greater than 243?  If you have done the PS curve correctly
the printer won't get any but I would pad the two ends with max ink load and
paper white, respectively.)

> From: Tyler Boley <tyler@...>

> 
> No, that will result in even further compression. 243 will map to a
> light gray instead of paper white, 45 will map to less than ink black,
> lowering your potential final density range.
> 
> Tyler
> www.custom-digital.com
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See ³Group Topic, Rules and Guidelines² in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE ³OWNER² AND
> ³MODERATORS² OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  ³OWNER² AND ³MODERATORS² OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Steve, we are conversing in circles and not quite meeting in the
middle. Sorry <G>.
There are many ways to address the wysiwyg problem, including preview
profiles which will map the paper white point and ink black point to
their corresponding monitor LAB values. Whether or not the "printer
gamma" matches the working space gamma depends on many many things,
including workflow, and they can actually be made to closely match if
necessary.
Tyler


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> Yes if all you did was do a PS curve compressing the image tonal
range to
> 45-243 then you would end up with an even flatter image.  This is
because
> you have compressed the image tonal range and done nothing with the
printer
> gamma.  But if instead I set up the printer such that a pixel value
of 45 is
> delivered a full ink load, a pixel value of 243 is given paper
white, and
> the points in between have the same gamma as the workspace then you
will get
> WYSISYG. In this case, I have equated the two environments (manually
because
> I don't have colorsync - we are using Same as Source, a non-colour
managed
> workflow).
> 
> The "WYSIWY don't G" problem is because the printer gamma (that which
> defines the rate of change of density produced from pixel value 0 to
value
> 255) is completely different from that of the workspace. The printer
goes
> from 0.043 (@ 255) to 1.65 (@ 0).  The display (and underlying image
values)
> goes from 0 (the calibrated white point, D50) to a maximum black way
beyond
> 1.65 in the same 8bit 0-255 range.
> 
> (You might then ask what would the printer do upon receiving pixel
values
> less than 45 and greater than 243?  If you have done the PS curve
correctly
> the printer won't get any but I would pad the two ends with max ink
load and
> paper white, respectively.)
> 
> 
> > From: Tyler Boley <tyler@t...>
> 
> > 
> > No, that will result in even further compression. 243 will map to a
> > light gray instead of paper white, 45 will map to less than ink black,
> > lowering your potential final density range.
> > 
> > Tyler
> > www.custom-digital.com
> > 
> > 
> > 
> > 
> > 
> > 
> > Please visit the Group Homepage to check the Files, and other
resources as
> > they are often being updated.
> > 
> > http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> > 
> > If you wish to receive no emails or just a daily digest, or you
wish to
> > unsubscribe, please edit your Membership preferences by visiting
this same
> > page.
> > 
> > Please follow these basic guidelines:
> > - As threads develop, trim off excess portions of earlier messages
to keep
> > them short.
> > - Good manners are required at all time. No personal attacks or
flames.
> > Hostile, aggressive or argumentative users may be removed from the
membership
> > without notice.
> > - Keep your posts and threads related to the group topic of
digital B&W
> > printing. Users who persistently make off-topic posts may be
removed from the
> > membership.
> > - By posting on this forum you agree to abide by the group rules and
> > guidelines, and to abide by the actions and decisions of the group
Owner and
> > Moderators. See ³Group Topic, Rules and Guidelines² in the Files
section:
> > http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> > 
> > BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE
PRINT
> > YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE ³OWNER² AND
> > ³MODERATORS² OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE
LIABLE TO YOU
> > FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR
EXEMPLARY
> > DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF
PROFITS, GOODWILL,
> > USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  ³OWNER² AND
³MODERATORS² OF
> > DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH
> > DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE
DIGITAL BW,
> > THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION
OF YOUR
> > TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD
PARTY ON THE
> > DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER
RELATING TO THE

> > DIGITAL BW, THE PRINT YAHOO GROUP.
> >  
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> >

Tyler

Yes I agree that there are many ways to replicate WYSIWYG.  But this
proposed workflow is not intended to revolve solely around that.  It is
intended to more clearly and explicitly relate the tonal range of the
printer into the final steps of the workflow process.

The big problem with today's setup is that there is a hidden transfer
function (a remapping of pixel and their density/luminance values) from
workspace to print space which is HIDDEN from the view of the user - it is
imbedded in the RIP code and curve generation process.  It does not conform
with the user's workspace.  What's more, the nature of this transfer
function - it's end points, representation of mid grey, and all other points
between - is different for every paper and ink combination!  Move from a
curve for matt paper such as EEM to a glossy "curve" on glossy paper and the
way all your mid tones are reproduced is different.  A PS adjustment curve
for one will not give the same result for another.  Over the last 2 years I
have witnessed hundreds if not thousands of posts on this forum which are
the symptoms of this problem.  People get their prints looking nice on
screen using the full tonal range available to them and then send it to the
printer without any understanding of the tonal range limitations of the
paper/ink combination they are using nor the way the printer will remap
their original (file's) tonal range to fit the narrower one.

Both the current methodology and the one I am proposing may get you to the
same point in the end, but I am reminded of Ansel Adams' remarks in Chapter
3 Exposure in his "The Ansel Adams Photography Series Book 2: The Negative":

"I can recall seeing Edward Weston....using his meter in rather unorthodox
ways. He would point it in several directions, take a reading from each, and
fiddle with the dial with a thoughtful expression.  "It says one-quarter
second at f32, I'll give one second."  His approach was empirical, based on
long experience combined with very deep sensitivity and intuition, and his
extraordinary results speak for themselves.  My own approach relies on
experience and intuition for the visualization of the image, but I prefer a
more methodical system for executing the visualized photograph."

Now I am not suggesting that the current setup isn't methodical but I am
suggesting that the current remapping of tonal range from the very broad
workspace to the narrow print space is not as clear nor intuitive as it
could very easily be.

(In all this discussion I will try to stick with a normalised pixel value
range of 0 - black - to 1 - white.  Things can get confusing because PS
levels uses a range of 0 (black) to 255 (white); PS curves use a range 0
(white) to 100 (black) or 0 (black) to 255 (white) depending on which way
they are set; and we print step wedges from 0 (white) to x (black) depending
on the number of steps!)

A good exercise is to plot the tonal response curve of gamma 2.2 (our
workspace) and overlay on top of that the tonal response curve of, say, a
QTR EEM ink curve.  By tonal response curve I mean log10(pixel value) on the
x axis and log10(luminance) [or -Density] on the y axis.  It is readily
clear that never the two shall meet.

Yet a printer/paper/ink combination has a natural tonal response curve which
is exactly analogous to photographic film or photographic paper.  At a
certain point, dmax of around 1.65 for EEM, we can't get it any darker by
throwing any more ink at the page - much the same way that we can't get a
photographic paper any darker by throwing more light through the NEGATIVE at
it - and at a certain point, around dMin of 0.04, we can't get it any whiter
because we have hit paper white.  The file pixel value of these two
inflexion points are readily calculated.

If we follow my proposed methodology, we align the two inflexion points with
their corresponding gamma 2.2 pixel values, anything outside this range
would "flat line" at the respective limit, and the points in between would
be "linearized" to a gamma of 2.2 (the same as our workspace).  Now plot
this tonal response curve.  Looking at the chart we would see a line
beginning flat at -dMax, inflecting at log10(45/255) where the printer's
tonal range begins and it can reproduce changes in density, travelling at a
slope of 2.2 to the next inflection point log10(243/255) and then
horizontal.  This curve should be readily identifiable with a photographic
paper curve.  It is also very intuitive.  The upward sloping portion of the
curve would overlay that of gamma 2.2 and would represent the "dynamic
range" (to use an Ansel Adams' Zone term) of the print space.

(Take a look at http://www.normankoren.com/makingfineprints1A.html )

Now turn to PS.  You've got the image looking great on the screen in the
very broad workspace Gray Gamma 2.2. (Actually not quite because our screen
also flat lines at some point in the deep black but this is so far outside
of the tonal range of the print space that we need not worry about it.)

Guys like Ansel were very conscious of the tonal range of their print space
all the way through there workflow.  They knew that they had to work to a
narrower range than the range of the scene.  After all, in most cases, the
tonal range of the scene > tonal range of the capture medium (film or
digital) > tonal range of the print space.  Tonal range compression
(principally through the use of filters) was necessary else clipping was a
reality.  The natural result was some mix of the two.  We are prepared to
sacrifice some loss of detail in the shadows (clipping) so long as the
important parts of the image are well in view.  The really cool thing about
digital is that we have much greater flexibility for managing this issue
(and for changing the setting of "Zone V" and hence we can with a digital
camera "expose to the right").

I would suggest that many digital photographers today are much less
conscious of the reduced tonal range of their print space at the time of
printing.  How many know how many f-stops is inherent in a range of density
from 0.04 to 1.65 or what pixel values can be faithfully reproduced with
this range?  This is manifested in all the complaints of my images print
lighter than on screen, they look flat, how do I get a good black etc etc.
Most just send their nice looking image to the printer and then wonder what
happened.  Gradually they learn to fiddle with S curves in PS and perhaps
even to use soft proof techniques.  But even a soft proof technique is a
very fiddly exercise - trying to realign the proofed image's relative tonal
situation to the un-proofed original. The curves are not conducted within
the readily identifiable pixel value range of the printer (those pixel
values that can be reproduced by the printer) and it involves second
guessing the other hidden transfer function imbedded in the RIP.

If on the other hand, the printer RIP is set up as I am proposing, I know
which pixels in my image will be clipped by the printer to either paper
white or dMax IF I SIMPLY SEND THE FILE AS IS.  Furthermore, and
importantly, I know that all OTHER pixels WILL be accurately reproduced.
(For Zone people, my Zone V will be faithfully where I set it.)  Take a look
at the PS curve that would adjust the file so that it sent only those pixels
that were within the dynamic range of the printer.  First of all it would
look like the tonal response curve of the print space (with just one
difference: the slope of the diagonal portion is 1:1 rather than 2.2:1).  It
also says that there is a 1:1 mapping of points, ie NO CHANGE, that sit
within the tonal range of the print space. Nice and intuitive.  Most likely,
we will then make a decision to not clip abruptly but rather smooth at the
extremes the adjustment in image tonal range required to fit the printer
tonal range - and so the PS curve is modified to some form of "S" curve but
the anchor points representing the two ends of the printer tonal range
remain in view.  (Furthermore, we can choose some clipping if we so desire.)
The PS curve in this case is very intuitive and we know that what we have in
this curve represents the ENTIRE tonal transformation that will take place -
nothing is hidden.

(Run through what would happen if we decided to print the same image on a
printer or paper and ink with greater tonal range.  We would extend the PS
curve's end points showing a wider dynamic range. Again very intuitive.)

Hopefully you can now see why I think this methodology is much more
transparent, intuitive, visual and, in the end, easier to comprehend.  To be
honest I am surprised that printer RIPs didn't evolve this was in the first
place because it is so analogous to the darkroom world.  If one were to
print a 101 step wedge (from 0 black to 1 white!), measure the densities and
plot the tonal response curve, a darkroom guy would immediately recognize
the graph!

As I commented to Roy last night, I do not have the programming skills to
write a RIP or modify one like QTR to put this to a practical demonstration.
But I do believe that this is a better basis for the work.

Food for thought over the weekend!!

:-)

Steve

Steve Kale wrote:
> Tyler
> 
> Yes I agree that there are many ways to replicate WYSIWYG.  But this
> proposed workflow is not intended to revolve solely around that.  It is
> intended to more clearly and explicitly relate the tonal range of the
> printer into the final steps of the workflow process.
> 
> The big problem with today's setup is that there is a hidden transfer
> function (a remapping of pixel and their density/luminance values) from
> workspace to print space which is HIDDEN from the view of the user - it is
> imbedded in the RIP code and curve generation process.  It does not conform
> with the user's workspace.  What's more, the nature of this transfer
> function - it's end points, representation of mid grey, and all other points
> between - is different for every paper and ink combination!  Move from a
> curve for matt paper such as EEM to a glossy "curve" on glossy paper and the
> way all your mid tones are reproduced is different.  A PS adjustment curve
> for one will not give the same result for another.  Over the last 2 years I
> have witnessed hundreds if not thousands of posts on this forum which are
> the symptoms of this problem.  People get their prints looking nice on
> screen using the full tonal range available to them and then send it to the
> printer without any understanding of the tonal range limitations of the
> paper/ink combination they are using nor the way the printer will remap
> their original (file's) tonal range to fit the narrower one.

Isn't photographic paper the same?

Part of the problem with the current process, is there are no givens.... 
    People think that they can change parts of the printing process, 
without needing to think about how that will change the process.

For example, say I have a darkroom print, printed on Ilford Multigrade 
RC paper, processed with Ilford's Multigrade Developer,  with copious 
notes on the way it was processed.  Now I move to  Agfa Multicontrast 
Classic, and switch to to Kodak Dektol as the developer, following my 
notes, will the two prints look identical.  Slim chance to none, the 
different papers have different sensitivity curves, and the developers 
work differently.

In the fume room, they resolve this, by only using only one or two 
papers, in fact you would probably only keep one type and brand of 
paper, with some in glossy, satin/pearl and matte finishes.  You would 
learn how the paper reacts to changes, and get fairly good after a 
while, at knowing what the result would look like, seeing the negative 
on the light table.


Same goes for digital printing, if you change the paper or ink or both, 
you should expect the result to look different.  This is why you would 
change the paper or ink or both in the first place.  For example, if I 
have a print on Kodak Ultima Picture Paper, and pop in a sheet of 
Hahnemm\ufffdhle Photo Rag, and print it again, I should expect to have a 
different result.  If I know how those two papers work, with that 
particular ink, in that particular printer, then I will know how I need 
to adjust the image for printing.  The other option is customized 
curves, so that they react the same......

W

> From: The Wogster <wogsterca@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 03 Dec 2004 09:57:44 -0500
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Steve Kale wrote:
>> Tyler
>> 
>> Yes I agree that there are many ways to replicate WYSIWYG.  But this
>> proposed workflow is not intended to revolve solely around that.  It is
>> intended to more clearly and explicitly relate the tonal range of the
>> printer into the final steps of the workflow process.
>> 
>> The big problem with today's setup is that there is a hidden transfer
>> function (a remapping of pixel and their density/luminance values) from
>> workspace to print space which is HIDDEN from the view of the user - it is
>> imbedded in the RIP code and curve generation process.  It does not conform
>> with the user's workspace.  What's more, the nature of this transfer
>> function - it's end points, representation of mid grey, and all other points
>> between - is different for every paper and ink combination!  Move from a
>> curve for matt paper such as EEM to a glossy "curve" on glossy paper and the
>> way all your mid tones are reproduced is different.  A PS adjustment curve
>> for one will not give the same result for another.  Over the last 2 years I
>> have witnessed hundreds if not thousands of posts on this forum which are
>> the symptoms of this problem.  People get their prints looking nice on
>> screen using the full tonal range available to them and then send it to the
>> printer without any understanding of the tonal range limitations of the
>> paper/ink combination they are using nor the way the printer will remap
>> their original (file's) tonal range to fit the narrower one.
> 
> Isn't photographic paper the same?

Yes and no. Each photographic paper has a defined and published tonal
response curve with its limits (dMin and dMax) and contrast or gamma.
Different photographic papers were made with different contrast ratios
BECAUSE that was the only way to alter contrast (one also could use a
different negative development but once the negative was developed the only
way to alter contrast was to select a different paper).

Digital provides a much more satisfying and flexible method for altering
contrast - within the digital file itself.  This is analogous to being able
to change the composition of the developed negative.

> 
> Part of the problem with the current process, is there are no givens....
>     People think that they can change parts of the printing process,
> without needing to think about how that will change the process.
> 
> For example, say I have a darkroom print, printed on Ilford Multigrade
> RC paper, processed with Ilford's Multigrade Developer,  with copious
> notes on the way it was processed.  Now I move to  Agfa Multicontrast
> Classic, and switch to to Kodak Dektol as the developer, following my
> notes, will the two prints look identical.  Slim chance to none, the
> different papers have different sensitivity curves, and the developers
> work differently.
> 
> In the fume room, they resolve this, by only using only one or two
> papers, in fact you would probably only keep one type and brand of
> paper, with some in glossy, satin/pearl and matte finishes.  You would
> learn how the paper reacts to changes, and get fairly good after a
> while, at knowing what the result would look like, seeing the negative
> on the light table.
> 
> 
> Same goes for digital printing, if you change the paper or ink or both,
> you should expect the result to look different.

But of course!  At a minimum they have a different dynamic range.  The
question is whether one SHOULD expect the gamma/contrast within the dynamic
range to change.  In a digital world this is unnecessary because we have a
much better method for altering the image file (the digital negative).
Worse yet - you would not want any change to not be transparent.  Better to
keep print space gamma at a known constant and alter the digital negative.


> This is why you would
> change the paper or ink or both in the first place.  For example, if I
> have a print on Kodak Ultima Picture Paper, and pop in a sheet of
> Hahnemmühle Photo Rag, and print it again, I should expect to have a
> different result.  If I know how those two papers work, with that
> particular ink, in that particular printer, then I will know how I need
> to adjust the image for printing.  The other option is customized
> curves, so that they react the same......
> 

When you swap papers are you aware of the exact change in tonal range and
more importantly to what extent and how the relative tonal range has
precisely changed?  I doubt it.  Rather through trial and error you (like
me) get a feel for the change and work against it.  Much like Mr Weston and
his light meter....

Once again:  in a darkroom world we had to change print space gamma because
once developed we had no mechanism for altering the negative.  In a digital
world, we have very precise tools for altering the digital negative.  It is
better that other factors remain constant and precisely predictable, or at
least very transparent.

Steve

Actually let me go one step further.  When Mr Adams made his prints with the
Zone System he could be assured that his Zone V ended up where he wanted it
(and he could alter print gamma/contrast) around it.  As currently
configured, mid grey shifts when we load one print curve vs another - even
though it did not shift in the digital negative.  Unfortunately, I believe,
we have gone a little backwards in our rigour and method.

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 03 Dec 2004 15:32:24 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> 
> 
> 
>> From: The Wogster <wogsterca@...>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Fri, 03 Dec 2004 09:57:44 -0500
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: Re: [Digital BW] Tonal range and linearization
>> 
>> 
>> Steve Kale wrote:
>>> Tyler
>>> 
>>> Yes I agree that there are many ways to replicate WYSIWYG.  But this
>>> proposed workflow is not intended to revolve solely around that.  It is
>>> intended to more clearly and explicitly relate the tonal range of the
>>> printer into the final steps of the workflow process.
>>> 
>>> The big problem with today's setup is that there is a hidden transfer
>>> function (a remapping of pixel and their density/luminance values) from
>>> workspace to print space which is HIDDEN from the view of the user - it is
>>> imbedded in the RIP code and curve generation process.  It does not conform
>>> with the user's workspace.  What's more, the nature of this transfer
>>> function - it's end points, representation of mid grey, and all other points
>>> between - is different for every paper and ink combination!  Move from a
>>> curve for matt paper such as EEM to a glossy "curve" on glossy paper and the
>>> way all your mid tones are reproduced is different.  A PS adjustment curve
>>> for one will not give the same result for another.  Over the last 2 years I
>>> have witnessed hundreds if not thousands of posts on this forum which are
>>> the symptoms of this problem.  People get their prints looking nice on
>>> screen using the full tonal range available to them and then send it to the
>>> printer without any understanding of the tonal range limitations of the
>>> paper/ink combination they are using nor the way the printer will remap
>>> their original (file's) tonal range to fit the narrower one.
>> 
>> Isn't photographic paper the same?
> 
> Yes and no. Each photographic paper has a defined and published tonal
> response curve with its limits (dMin and dMax) and contrast or gamma.
> Different photographic papers were made with different contrast ratios
> BECAUSE that was the only way to alter contrast (one also could use a
> different negative development but once the negative was developed the only
> way to alter contrast was to select a different paper).
> 
> Digital provides a much more satisfying and flexible method for altering
> contrast - within the digital file itself.  This is analogous to being able
> to change the composition of the developed negative.
> 
>> 
>> Part of the problem with the current process, is there are no givens....
>>     People think that they can change parts of the printing process,
>> without needing to think about how that will change the process.
>> 
>> For example, say I have a darkroom print, printed on Ilford Multigrade
>> RC paper, processed with Ilford's Multigrade Developer,  with copious
>> notes on the way it was processed.  Now I move to  Agfa Multicontrast
>> Classic, and switch to to Kodak Dektol as the developer, following my
>> notes, will the two prints look identical.  Slim chance to none, the
>> different papers have different sensitivity curves, and the developers
>> work differently.
>> 
>> In the fume room, they resolve this, by only using only one or two
>> papers, in fact you would probably only keep one type and brand of
>> paper, with some in glossy, satin/pearl and matte finishes.  You would
>> learn how the paper reacts to changes, and get fairly good after a
>> while, at knowing what the result would look like, seeing the negative
>> on the light table.
>> 
>> 
>> Same goes for digital printing, if you change the paper or ink or both,
>> you should expect the result to look different.
> 
> But of course!  At a minimum they have a different dynamic range.  The
> question is whether one SHOULD expect the gamma/contrast within the dynamic
> range to change.  In a digital world this is unnecessary because we have a
> much better method for altering the image file (the digital negative).
> Worse yet - you would not want any change to not be transparent.  Better to
> keep print space gamma at a known constant and alter the digital negative.
> 
> 
>> This is why you would
>> change the paper or ink or both in the first place.  For example, if I
>> have a print on Kodak Ultima Picture Paper, and pop in a sheet of
>> Hahnemmühle Photo Rag, and print it again, I should expect to have a
>> different result.  If I know how those two papers work, with that
>> particular ink, in that particular printer, then I will know how I need
>> to adjust the image for printing.  The other option is customized
>> curves, so that they react the same......
>> 
> 
> When you swap papers are you aware of the exact change in tonal range and
> more importantly to what extent and how the relative tonal range has
> precisely changed?  I doubt it.  Rather through trial and error you (like
> me) get a feel for the change and work against it.  Much like Mr Weston and
> his light meter....
> 
> Once again:  in a darkroom world we had to change print space gamma because
> once developed we had no mechanism for altering the negative.  In a digital
> world, we have very precise tools for altering the digital negative.  It is
> better that other factors remain constant and precisely predictable, or at
> least very transparent.
> 
> Steve
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See ³Group Topic, Rules and Guidelines² in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE ³OWNER² AND
> ³MODERATORS² OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  ³OWNER² AND ³MODERATORS² OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
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> 
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>...As currently configured, mid grey shifts when we load one 
>print curve vs another - even though it did not shift in the 
>digital negative...

No with my curves -- although, of course, the tolerances & consistency of
our systems are not perfect.

The simple bottom line question for me is what that midpoint target should
be.  Does a target of Lab L=50 (about visual density 0.73) come closer to
what you think would be the best midpoint target?  I assume you think the
midpoint target should match the monitors, which I fear may vary.  As I
noted earlier, I've been consistently using 0.61, but the L=50, which is
also the Kodak standard gray card density, has a lot of appeal to me on at
least some levels.

Paul
www.PaulRoark.com

Hi Paul

Yes you are right because you in effect manually set the 50% grey slot
(presumably with some iteration).  My comment was made in relation to a
programme such as QTR where the midpoint is a function of linearization.  I
caught my generalization after hitting send and thought I might hear from
you!  My rather simple point is that the mid point (and all other points in
the printer's tonal range) ideally would be the same as the workspace
(whatever one chooses that to be) else there is a transfer function
occurring that is not readily visible (nor intuitive) to the user.

I do not know how you go about the process of setting your curves but can
only suspect it must be quite a fiddly and iterative process.  You also have
the disadvantage of working with a closed box - the Epson driver. It does
what it does and you work around it/with it.  In an open system, one can
consider whether things inside the box could be better arranged another way.

Cheers

Steve

> From: Paul Roark <paul.roark@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 3 Dec 2004 08:21:06 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Tonal range and linearization
> 
> 
>> ...As currently configured, mid grey shifts when we load one
>> print curve vs another - even though it did not shift in the
>> digital negative...
> 
> Not with my curves -- although, of course, the tolerances & consistency of
> our systems are not perfect.
> 
> The simple bottom line question for me is what that midpoint target should
> be.  Does a target of Lab L=50 (about visual density 0.73) come closer to
> what you think would be the best midpoint target?  I assume you think the
> midpoint target should match the monitors, which I fear may vary.  As I
> noted earlier, I've been consistently using 0.61, but the L=50, which is
> also the Kodak standard gray card density, has a lot of appeal to me on at
> least some levels.
> 
> Paul
> www.PaulRoark.com
> 
>  
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
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> - Good manners are required at all time. No personal attacks or flames.
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> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See „Group Topic, Rules and Guidelines‰ in the Files section:
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> 
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> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE „OWNER‰ AND
> „MODERATORS‰ OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  „OWNER‰ AND „MODERATORS‰ OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Steve,

>Yes you are right because you in effect manually set the 50% grey slot
>(presumably with some iteration).  My comment was made in relation to a
>programme such as QTR where the midpoint is a function of linearization...

Yes, it is an iterative process.  The driver is a bit of a black box, but
once one gets used to it, it's quite predictable.

But, back to the simple question, would L=50 be a better midpoint?  If you
print a 21-step test strip, like one at
http://home1.gte.net/res09aij/Test-files.htm, would it match the monitor
better if the midpoint were more like density 0.73 (a bit lighter than the
current 60%) than the current 50% = 0.61?  

Paul
www.PaulRoark.com

Hello Steve,

>Actually let me go one step further.  When Mr Adams made his 
>prints with the Zone System he could be assured that his Zone 
>V ended up where he wanted it (and he could alter print 
>gamma/contrast) around it.  As currently configured, mid grey 
>shifts when we load one print curve vs another - even though 
>it did not shift in the digital negative.  Unfortunately, I 
>believe, we have gone a little backwards in our rigour and 
>method.

I have been following this with interest (I especially love your "fume
room" LOL! and enjoyed your Adams and Weston quotes).  You make some
very interesting points.  They seem to have good meaning but I confess
I am missing something when it comes to imagining practical
application, and it may be caused by the way I work.

My BO workflow is a very intuitive one, and my fume room thinking has
adapted nicely to it - IOW, I still think in S-curve terms as I work.
Further, because BO doesn't allow changing tone (color), it requires
using different papers to achieve various warm/cool results.  This is
another thing about BO that is somewhat analogous to wet print work. 
I have a small handful of favorite papers.

I'm finding that my S-curve thinking adapts nicely because once I've
finished working up an image using EEM for proofs, I can now print it
on any other paper by applying a curve adj layer for whatever papers I
want to try, and then choosing the appropriate curve each time I make
a print.   For example, for an image I've been using for some
experiments I have curves for BO Merlin, BO Condor, and UT7 Condor. 
Another one has curves for BO PR, BO Aurora and UT7 PR, and so on. 
These curves are attached to the image and I just switch on the one I
want.

I have arrived at this methodology through the photographic intuitive
process as Claude described, and am now at the point where I can
devise a new curve very quickly (tweak the curve until the print
matches the contrast of the EEM proof using very small quick prints).
I have gotten familiar with the properties of the few papers I like
and pretty well know where to start and am already "in the ball park"
the first go-round.  

I find this to be a very enjoyable and satisfying way to work, and I
think it's partly because it's very similar to they way I worked in
the fume room (love that!).  I was a Fred Picker type Zonie, which I
found to be a good balance between being particular about results and
KISS.  I still feel like I'm working photographically, and my mind is
not full of gamma/black point/etc concepts.  I mentally see each paper
in terms of its S-curve characteristics and tone (how it renders
Eboni), much as I did in the fume room days.

The point of all this is I'm wondering how your ideas can hook into
what I'm doing.  How can I benefit from it?   Your concepts are
expressed in very technical terms, but can they be applied in my
intuitive S-curve way of thinking and adjustment curve workflow?  

Regards,
Clayton


Info on black and white digital printing at    
http://www.cjcom.net/digiprnarts.htm

Sorry, is this meant to be a subjective empirical test? Ie which do I
subjectively prefer?

I use a workspace of Gray Gamma 2.2.  Someone who knows the intricacies of
this space better than I may correct me, but I would say that if:

Luminance = C * value^gamma + black level

(taken from Norman Koren's site)

And we can usefully set C and black level to 1 and 0 respectively, then a
normalised pixel value will have a luminance of 0.2176. If

Density = - log10(luminance)

Then it will have a density of -0.61.  Given it is a reflected density this
then is 0.61.  That is, to match the workspace I would say it should print
with a density of 0.61.

I thought I had read somewhere that PS uses LAB as the intermediate colour
space when converting from one space to another.  I also thought LAB had a
gamma of 2.2.  Perhaps I am wrong on this.

> From: Paul Roark <paul.roark@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 3 Dec 2004 08:51:49 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Tonal range and linearization
> 
> 
> Steve,
> 
>> Yes you are right because you in effect manually set the 50% grey slot
>> (presumably with some iteration).  My comment was made in relation to a
>> programme such as QTR where the midpoint is a function of linearization...
> 
> Yes, it is an iterative process.  The driver is a bit of a black box, but
> once one gets used to it, it's quite predictable.
> 
> But, back to the simple question, would L=50 be a better midpoint?  If you
> print a 21-step test strip, like one at
> http://home1.gte.net/res09aij/Test-files.htm, would it match the monitor
> better if the midpoint were more like density 0.73 (a bit lighter than the
> current 60%) than the current 50% = 0.61?
> 
> Paul
> www.PaulRoark.com
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See „Group Topic, Rules and Guidelines‰ in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE „OWNER‰ AND
> „MODERATORS‰ OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  „OWNER‰ AND „MODERATORS‰ OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Hi Clayton

The immediate answer to your question at the bottom is that there is nothing
you can do about it because you (much like Paul) can't get inside the Epson
driver.  In your workflow, the Epson driver - not you - decides what to do
when it gets a (normalised) pixel value of 0 or 1 and all points in between.
I, nor you, don't know what transfer function is within the black box.  This
is analogous to letting a camera do the RAW conversion.  The transfer
function is not open and there is within an implicit trade-off between
dynamic range and contrast.  As a result, if you were to start anew you
print an image and look at it.  Apply a curve to adjust it and reprint.  At
this point there are two transfer functions at work:  the curve you just did
in PS and the curve embedded in the driver.  It's quite difficult to
visualise something you can't see.  Rather you develop feel by iterative
experience. In an open RIP we get the opportunity to define the transfer
function, potentially making it better suited to a more tonal range
conscious workflow.

Your workflow is the simplest of them all.  You work with one ink (until a
better one comes along).  You work with a box that you can't alter nor see
inside - you take what it gives.  And you change paper to change your white
point and dMax.  Nothing wrong with this - it is very simple. But again your
PS curve is not done with the tonal range limits of the printer/ink/paper
combination at the forefront.

An interesting test would be to print a step wedge in the normal fashion and
measure the results.  Then use an abrupt clipping curve to constrain the
image file to the tonal range of that same combination (say output values of
45 to 243 only, roughly EEM) and print this.  In either case the range of
tones able to be produced by the printer have not changed and in one case we
have simply fed it an in-range image.  In the other we have purposefully
sent a range of tones that we know can't be reproduced.  How do the two
images compare?

Cheers

Steve

> From: Clayton Jones <cj@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 03 Dec 2004 17:16:41 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> 
> Hello Steve,
> 
>> Actually let me go one step further.  When Mr Adams made his
>> prints with the Zone System he could be assured that his Zone
>> V ended up where he wanted it (and he could alter print
>> gamma/contrast) around it.  As currently configured, mid grey
>> shifts when we load one print curve vs another - even though
>> it did not shift in the digital negative.  Unfortunately, I
>> believe, we have gone a little backwards in our rigour and
>> method.
> 
> I have been following this with interest (I especially love your "fume
> room" LOL! and enjoyed your Adams and Weston quotes).  You make some
> very interesting points.  They seem to have good meaning but I confess
> I am missing something when it comes to imagining practical
> application, and it may be caused by the way I work.
> 
> My BO workflow is a very intuitive one, and my fume room thinking has
> adapted nicely to it - IOW, I still think in S-curve terms as I work.
> Further, because BO doesn't allow changing tone (color), it requires
> using different papers to achieve various warm/cool results.  This is
> another thing about BO that is somewhat analogous to wet print work.
> I have a small handful of favorite papers.
> 
> I'm finding that my S-curve thinking adapts nicely because once I've
> finished working up an image using EEM for proofs, I can now print it
> on any other paper by applying a curve adj layer for whatever papers I
> want to try, and then choosing the appropriate curve each time I make
> a print.   For example, for an image I've been using for some
> experiments I have curves for BO Merlin, BO Condor, and UT7 Condor.
> Another one has curves for BO PR, BO Aurora and UT7 PR, and so on.
> These curves are attached to the image and I just switch on the one I
> want.
> 
> I have arrived at this methodology through the photographic intuitive
> process as Claude described, and am now at the point where I can
> devise a new curve very quickly (tweak the curve until the print
> matches the contrast of the EEM proof using very small quick prints).
> I have gotten familiar with the properties of the few papers I like
> and pretty well know where to start and am already "in the ball park"
> the first go-round.
> 
> I find this to be a very enjoyable and satisfying way to work, and I
> think it's partly because it's very similar to they way I worked in
> the fume room (love that!).  I was a Fred Picker type Zonie, which I
> found to be a good balance between being particular about results and
> KISS.  I still feel like I'm working photographically, and my mind is
> not full of gamma/black point/etc concepts.  I mentally see each paper
> in terms of its S-curve characteristics and tone (how it renders
> Eboni), much as I did in the fume room days.
> 
> The point of all this is I'm wondering how your ideas can hook into
> what I'm doing.  How can I benefit from it?   Your concepts are
> expressed in very technical terms, but can they be applied in my
> intuitive S-curve way of thinking and adjustment curve workflow?
> 
> Regards,
> Clayton
> 
> 
> Info on black and white digital printing at
> http://www.cjcom.net/digiprnarts.htm
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See ³Group Topic, Rules and Guidelines² in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE ³OWNER² AND
> ³MODERATORS² OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  ³OWNER² AND ³MODERATORS² OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Steve,

>Sorry, is this meant to be a subjective empirical test? Ie which do I
>subjectively prefer?

Perhaps it’s an objective empirical test.  

I think there are a few bottom line, practical and useful goals.  Matching
the monitor would be one of those.  For this, some average lighting and
viewing conditions is going to have to be assumed.  Also, I don't know if
the calibration programs are very standardized.  But, if one did a pole of
actual users, then those factors would be included in the responses.

So, the question is, empirically, what midtone 50% print density best
matches the monitor.

Your numbers, below, suggest that by at least some theory my current target
of 0.61 might be "correct."  I also have a theory as to why it is "correct,"
but I also have a theory that suggests it is too light.  Frankly, I based my
0.61 standard on an empirical averaging of my and others' Piezo outputs some
years ago, where consistency with old files was the main concern.
Currently, however, I'd say most seem to think that the 0.61 50% target is
too light.  I assume these people are basically saying that the prints are
"lighter" appearing than their monitors.  As such they need to go through
some cumbersome process to match the two.  If that matching were better
built into the target, it might make life easier for many.

(Although I was once a math major, my experience has convinced me that
surveys and other empirical studies result in the best models.)

Paul
www.PaulRoark.com 





>I use a workspace of Gray Gamma 2.2.  Someone who knows the intricacies of
>this space better than I may correct me, but I would say that if:

>Luminance = C * value^gamma + black level

>(taken from Norman Koren's site)

>And we can usefully set C and black level to 1 and 0 respectively, then a
>normalised pixel value will have a luminance of 0.2176. If

>Density = - log10(luminance)

>Then it will have a density of -0.61.  Given it is a reflected density this
>then is 0.61.  That is, to match the workspace I would say it should print
>with a density of 0.61.

>I thought I had read somewhere that PS uses LAB as the intermediate colour
>space when converting from one space to another.  I also thought LAB had a
>gamma of 2.2.  Perhaps I am wrong on this.





________________________________
> From: Paul Roark <paul.roark@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 3 Dec 2004 08:51:49 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Tonal range and linearization
> 
> 
> Steve,
> 
>> Yes you are right because you in effect manually set the 50% grey slot
>> (presumably with some iteration).  My comment was made in relation to a
>> programme such as QTR where the midpoint is a function of
linearization...
> 
> Yes, it is an iterative process.  The driver is a bit of a black box, but
> once one gets used to it, it's quite predictable.
> 
> But, back to the simple question, would L=50 be a better midpoint?  If you
> print a 21-step test strip, like one at
> http://home1.gte.net/res09aij/Test-files.htm, would it match the monitor
> better if the midpoint were more like density 0.73 (a bit lighter than the
> current 60%) than the current 50% = 0.61?
> 
> Paul
> www.PaulRoark.com
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the
membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from
the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner
and
> Moderators. See „Group Topic, Rules and Guidelines‰ in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE „OWNER‰ AND
> „MODERATORS‰ OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO
YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS,
GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  „OWNER‰ AND
„MODERATORS‰ OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF
SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL
BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON
THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO
THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 





Please visit the Group Homepage to check the Files, and other resources as
they are often being updated.

http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint

If you wish to receive no emails or just a daily digest, or you wish to
unsubscribe, please edit your Membership preferences by visiting this same
page.

Please follow these basic guidelines:
- As threads develop, trim off excess portions of earlier messages to keep
them short.
- Good manners are required at all time. No personal attacks or flames.
Hostile, aggressive or argumentative users may be removed from the
membership without notice.
- Keep your posts and threads related to the group topic of digital B&W
printing. Users who persistently make off-topic posts may be removed from
the membership.
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FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
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GOODWILL, USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  OWNER AND
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POSSIBILITY OF SUCH DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY
TO USE THE DIGITAL BW, THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR
ALTERATION OF YOUR TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY
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Paul

My answer was based on simple maths as you say defined by the parameters of
a gamma = 2.2 space such as Gray Gamma 2.2 or even SRGB.  If the monitor and
printer are properly calibrated this mid point should print with a density
of 0.61 and match the screen.  Whether people, when looking at the scale,
would agree that 50% at D = 0.61 or a block of pixels with normalised vales
of 0.5 displayed on a Gray Gamma 2.2 screen are fair descriptions of "middle
grey" is entirely different question.

Ansel defined mid grey at 18% reflectance, decided which part of the scene
he wanted to have 18% reflectance in the final print and then let all the
other parts fall where they lay. I haven't been through it yet but it is
interesting to note on Norman Koren's site (again):

http://www.normankoren.com/zonesystem.html

"The charts below are derived from an equation intended to make zone 5 on a
properly calibrated monitor appear as subjective middle gray‹ about 21% of
the maximum screen brightness level, similar to middle gray on a print (18%
reflectance referenced to 90% white). I include the equation in a box near
the end."

When you pull up a step wedge on screen and run the cursor over it examining
the luminance levels you might show D = 61 on screen.  But when it comes to
printing the Epson driver (without benefit of colorsync) performs a tonal
compression.  If your curve shifts 50% = 0.61 so that it prints fine, I am
not sure that a displayed and curve adjusted 50% step is still at pixel
value 0.5.  (But in my proposed methodology where I have access to the
inside of the RIP I could be assured that norm PV = 0.5 prints at 0.61
because any and all tonal adjustments are in my single PS curve.)

Steve

> From: Paul Roark <paul.roark@...>
> 
> So, the question is, empirically, what midtone 50% print density best
> matches the monitor.
> 
> Your numbers, below, suggest that by at least some theory my current target
> of 0.61 might be "correct."  I also have a theory as to why it is "correct,"
> but I also have a theory that suggests it is too light.  Frankly, I based my
> 0.61 standard on an empirical averaging of my and others' Piezo outputs some
> years ago, where consistency with old files was the main concern.
> Currently, however, I'd say most seem to think that the 0.61 50% target is
> too light.  I assume these people are basically saying that the prints are
> "lighter" appearing than their monitors.  As such they need to go through
> some cumbersome process to match the two.  If that matching were better
> built into the target, it might make life easier for many.
> 
> (Although I was once a math major, my experience has convinced me that
> surveys and other empirical studies result in the best models.)
> 
> Paul
> www.PaulRoark.com
> 
>

Actually, what does one of your curves do at norm PV = 0.5 in order to get
the 50% step = 0.61 density?  Is it shifted at all?   (128 or 50% if your
prefer)

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 03 Dec 2004 19:07:03 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Paul
> 
> My answer was based on simple maths as you say defined by the parameters of
> a gamma = 2.2 space such as Gray Gamma 2.2 or even SRGB.  If the monitor and
> printer are properly calibrated this mid point should print with a density
> of 0.61 and match the screen.  Whether people, when looking at the scale,
> would agree that 50% at D = 0.61 or a block of pixels with normalised vales
> of 0.5 displayed on a Gray Gamma 2.2 screen are fair descriptions of "middle
> grey" is entirely different question.
> 
> Ansel defined mid grey at 18% reflectance, decided which part of the scene
> he wanted to have 18% reflectance in the final print and then let all the
> other parts fall where they lay. I haven't been through it yet but it is
> interesting to note on Norman Koren's site (again):
> 
> http://www.normankoren.com/zonesystem.html
> 
> "The charts below are derived from an equation intended to make zone 5 on a
> properly calibrated monitor appear as subjective middle gray‹ about 21% of
> the maximum screen brightness level, similar to middle gray on a print (18%
> reflectance referenced to 90% white). I include the equation in a box near
> the end."
> 
> When you pull up a step wedge on screen and run the cursor over it examining
> the luminance levels you might show D = 61 on screen.  But when it comes to
> printing the Epson driver (without benefit of colorsync) performs a tonal
> compression.  If your curve shifts 50% = 0.61 so that it prints fine, I am
> not sure that a displayed and curve adjusted 50% step is still at pixel
> value 0.5.  (But in my proposed methodology where I have access to the
> inside of the RIP I could be assured that norm PV = 0.5 prints at 0.61
> because any and all tonal adjustments are in my single PS curve.)
> 
> Steve

Paul 

Sorry, I made a mistake when I did the calculations below.  A normalised
pixel value of 0.5 equates to a density of 0.6623 in a gray gamma 2.2 space
(via the math previously outlined).  Not 0.61. So yes if you are getting a
density of 0.61 for your 50% step then you are printing lighter than the
screen. 

Another way of looking at this is to open your step wedge in PS and run the
eye-dropper over it while looking in the Info Tab.  At 50% you have a pixel
value of 0.5 (shown by K=50%) and a LAB value of L=54. Carl Schofield
previously provided the following formula for calculating density from LAB's
L value.

If L>8 then Y = ((L+16)/116)^3

Else Y = (L*27)/24389

And Density = -Log10(Y)

With L = 54 this would yield a density of 0.6581

To be honest I have no idea why the two formulas end up with a different
value...

Either way I would expect your 50 step to have a density of 0.66 and if it
is showing 0.61 then I would say it is perhaps not surprising people think
it is printing lighter than on screen.

Cheers

Steve

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 03 Dec 2004 17:21:24 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Sorry, is this meant to be a subjective empirical test? Ie which do I
> subjectively prefer?
> 
> I use a workspace of Gray Gamma 2.2.  Someone who knows the intricacies of
> this space better than I may correct me, but I would say that if:
> 
> Luminance = C * value^gamma + black level
> 
> (taken from Norman Koren's site)
> 
> And we can usefully set C and black level to 1 and 0 respectively, then a
> normalised pixel value will have a luminance of 0.2176. If
> 
> Density = - log10(luminance)
> 
> Then it will have a density of -0.61.  Given it is a reflected density this
> then is 0.61.  That is, to match the workspace I would say it should print
> with a density of 0.61.
> 
> I thought I had read somewhere that PS uses LAB as the intermediate colour
> space when converting from one space to another.  I also thought LAB had a
> gamma of 2.2.  Perhaps I am wrong on this.
> 
>> From: Paul Roark <paul.roark@verizon.net>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Fri, 3 Dec 2004 08:51:49 -0800
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: RE: [Digital BW] Tonal range and linearization
>> 
>> 
>> Steve,
>> 
>>> Yes you are right because you in effect manually set the 50% grey slot
>>> (presumably with some iteration).  My comment was made in relation to a
>>> programme such as QTR where the midpoint is a function of linearization...
>> 
>> Yes, it is an iterative process.  The driver is a bit of a black box, but
>> once one gets used to it, it's quite predictable.
>> 
>> But, back to the simple question, would L=50 be a better midpoint?  If you
>> print a 21-step test strip, like one at
>> http://home1.gte.net/res09aij/Test-files.htm, would it match the monitor
>> better if the midpoint were more like density 0.73 (a bit lighter than the
>> current 60%) than the current 50% = 0.61?
>> 
>> Paul
>> www.PaulRoark.com
>> 
>> 
>> 
>> 
>> 
>> Please visit the Group Homepage to check the Files, and other resources as
>> they are often being updated.
>> 
>> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>> 
>> If you wish to receive no emails or just a daily digest, or you wish to
>> unsubscribe, please edit your Membership preferences by visiting this same
>> page.
>> 
>> Please follow these basic guidelines:
>> - As threads develop, trim off excess portions of earlier messages to keep
>> them short.
>> - Good manners are required at all time. No personal attacks or flames.
>> Hostile, aggressive or argumentative users may be removed from the membership
>> without notice.
>> - Keep your posts and threads related to the group topic of digital B&W
>> printing. Users who persistently make off-topic posts may be removed from the
>> membership.
>> - By posting on this forum you agree to abide by the group rules and
>> guidelines, and to abide by the actions and decisions of the group Owner and
>> Moderators. See „Group Topic, Rules and Guidelines‰ in the Files section:
>> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
>> 
>> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
>> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE „OWNER‰ AND
>> „MODERATORS‰ OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
>> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
>> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
>> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  „OWNER‰ AND „MODERATORS‰
>> OF
>> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF
>> SUCH
>> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
>> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
>> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
>> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
>> DIGITAL BW, THE PRINT YAHOO GROUP.
>>  
>> Yahoo! Groups Links
>> 
>> 
>> 
>>  
>> 
>> 
>> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
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> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See �Group Topic, Rules and Guidelines� in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE �OWNER� AND
> �MODERATORS� OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  �OWNER� AND �MODERATORS� OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Steve,

>...A normalized pixel value of 0.5 equates to a density of 0.6623 ...

OK, then that is consistent with the average comment being that the prints are a bit lighter than the monitor image.

>...Carl Schofield previously provided the following formula 
>for calculating density from LAB's L value.

>If L>8 then Y = ((L+16)/116)^3

>Else Y = (L*27)/24389

>And Density = -Log10(Y)

>With L = 54 this would yield a density of 0.6581

>To be honest I have no idea why the two formulas end up with a different
>value...

>...
>Actually, what does one of your curves do at norm PV = 0.5 in order to get
>the 50% step = 0.61 density?  Is it shifted at all?   (128 or 50% if your
>prefer

Most of the curves require that a grayscale file be converted to Adobe RGB first.  Then the RGB curves map to the CMY inks, black being generated by a combination of the curves.  So, the RGB curves provide input-output relationships that allow me to specify the density of the image at each point.  It's just using Photoshop curves and the driver controls or built-in characteristics (including cross-overs) to do most of what RIPs do.

>...
>Ansel defined mid grey at 18% reflectance, ...

My Kodak standard gray, which I believe is 18% reflectance, reads as Lab L=50 with my X-Rite.  That is more like 0.73 density.

So, bottom line, what I'm hearing is that 0.66 might be closer to the mark as far as a standard midpoint density for the final print.

I generally like the idea of having a standard midpoint as opposed to cutting the total range in half.  I think the standard midpoint makes it easier to print the same image on different papers without having to re-do the file.

Interesting stuff, but it's too easy to get hung up in the numbers and ignore the aesthetics of the image.

Paul
www.PaulRoark.com 

__________________



> From: Steve Kale <stevekale@btinternet.com>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 03 Dec 2004 17:21:24 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Sorry, is this meant to be a subjective empirical test? Ie which do I
> subjectively prefer?
> 
> I use a workspace of Gray Gamma 2.2.  Someone who knows the intricacies of
> this space better than I may correct me, but I would say that if:
> 
> Luminance = C * value^gamma + black level
> 
> (taken from Norman Koren's site)
> 
> And we can usefully set C and black level to 1 and 0 respectively, then a
> normalised pixel value will have a luminance of 0.2176. If
> 
> Density = - log10(luminance)
> 
> Then it will have a density of -0.61.  Given it is a reflected density this
> then is 0.61.  That is, to match the workspace I would say it should print
> with a density of 0.61.
> 
> I thought I had read somewhere that PS uses LAB as the intermediate colour
> space when converting from one space to another.  I also thought LAB had a
> gamma of 2.2.  Perhaps I am wrong on this.
> 
>> From: Paul Roark <paul.roark@...>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Fri, 3 Dec 2004 08:51:49 -0800
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: RE: [Digital BW] Tonal range and linearization
>> 
>> 
>> Steve,
>> 
>>> Yes you are right because you in effect manually set the 50% grey slot
>>> (presumably with some iteration).  My comment was made in relation to a
>>> programme such as QTR where the midpoint is a function of linearization...
>> 
>> Yes, it is an iterative process.  The driver is a bit of a black box, but
>> once one gets used to it, it's quite predictable.
>> 
>> But, back to the simple question, would L=50 be a better midpoint?  If you
>> print a 21-step test strip, like one at
>> http://home1.gte.net/res09aij/Test-files.htm, would it match the monitor
>> better if the midpoint were more like density 0.73 (a bit lighter than the
>> current 60%) than the current 50% = 0.61?
>> 
>> Paul
>> www.PaulRoark.com
>> 
>> 
>> 
>> 
>> 
>> Please visit the Group Homepage to check the Files, and other resources as
>> they are often being updated.
>> 
>> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
>> 
>> If you wish to receive no emails or just a daily digest, or you wish to
>> unsubscribe, please edit your Membership preferences by visiting this same
>> page.
>> 
>> Please follow these basic guidelines:
>> - As threads develop, trim off excess portions of earlier messages to keep
>> them short.
>> - Good manners are required at all time. No personal attacks or flames.
>> Hostile, aggressive or argumentative users may be removed from the membership
>> without notice.
>> - Keep your posts and threads related to the group topic of digital B&W
>> printing. Users who persistently make off-topic posts may be removed from the
>> membership.
>> - By posting on this forum you agree to abide by the group rules and
>> guidelines, and to abide by the actions and decisions of the group Owner and
>> Moderators. See „Group Topic, Rules and Guidelines‰ in the Files section:
>> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
>> 
>> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
>> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE „OWNER‰ AND
>> „MODERATORS‰ OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
>> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
>> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
>> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  „OWNER‰ AND „MODERATORS‰
>> OF
>> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF
>> SUCH
>> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
>> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
>> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
>> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
>> DIGITAL BW, THE PRINT YAHOO GROUP.
>>  
>> Yahoo! Groups Links
>> 
>> 
>> 
>>  
>> 
>> 
>> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See �Group Topic, Rules and Guidelines� in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE �OWNER� AND
> �MODERATORS� OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  �OWNER� AND �MODERATORS� OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 





Please visit the Group Homepage to check the Files, and other resources as they are often being updated.

http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint

If you wish to receive no emails or just a daily digest, or you wish to unsubscribe, please edit your Membership preferences by visiting this same page.

Please follow these basic guidelines:
- As threads develop, trim off excess portions of earlier messages to keep them short.
- Good manners are required at all time. No personal attacks or flames. Hostile, aggressive or argumentative users may be removed from the membership without notice.
- Keep your posts and threads related to the group topic of digital B&W printing. Users who persistently make off-topic posts may be removed from the membership.
- By posting on this forum you agree to abide by the group rules and guidelines, and to abide by the actions and decisions of the group Owner and Moderators. See Group Topic, Rules and Guidelines in the Files section:
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BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE OWNER AND MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL, USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  OWNER AND MODERATORS OF DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW, THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE DIGITAL BW, THE PRINT YAHOO GROUP.
 
Yahoo! Groups Links

> From: Paul Roark <paul.roark@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Fri, 3 Dec 2004 14:19:29 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Tonal range and linearization
> 
> 
> Steve,
> 
> OK, then that is consistent with the average comment being that the prints are
> a bit lighter than the monitor image.
> 

Yes.  Once you understand the relationships between what is in the file, on
screen and on the print (and actually how they relate to their darkroom
counterparts if you started out that way) then this becomes useful.  Take a
look at the other steps as well.  When you ask your question do you simply
show a big 50% step on screen and print (no other steps)?  Remember the
other steps will be off to a greater extent.  If someone is looking at the
whole step wedge - even if you ask them about the 50% step only - they may
also be swayed by the other steps due to "brightness induction".  I recently
stumbled across this website which has a couple of interesting tests:

http://www.nebulus.org/tutorials/2d/photoshop/color/color3.html

> Most of the curves require that a grayscale file be converted to Adobe RGB
> first.  Then the RGB curves map to the CMY inks, black being generated by a
> combination of the curves.  So, the RGB curves provide input-output
> relationships that allow me to specify the density of the image at each point.
> It's just using Photoshop curves and the driver controls or built-in
> characteristics (including cross-overs) to do most of what RIPs do.

Yep.  I was wondering how mid grey (50% or 128) was modified.  I haven't
seen any of your curves. How 50% maps to your print result is a function of
(a) your curves and (b) the transfer function buried in the Epson driver and
even more complicated by the fact that the Epson driver is expecting totally
different inks.  So not transparent like a RIP but you do get amazing
results.  I love The Narrows photo on your site.

> 
> My Kodak standard gray, which I believe is 18% reflectance, reads as Lab L=50
> with my X-Rite.  That is more like 0.73 density.
> 
> So, bottom line, what I'm hearing is that 0.66 might be closer to the mark as
> far as a standard midpoint density for the final print.

If you have a gamma of 2.2 for the monitor yes.  It will, I believe, be
different for each gamma.

> 
> I generally like the idea of having a standard midpoint as opposed to cutting
> the total range in half.

Not sure what you mean by cutting the tonal range in half. I would never
propose doing so either. But if I had a system whereby the in-gamut tonal
range was reproduced faithfully then I could on screen look at my image in
that tonal range space and compress (or clip) in the manner I choose. In
this environment, the only transfer function at work is my one PS "print"
curve.

> I think the standard midpoint makes it easier to
> print the same image on different papers without having to re-do the file.

You would never need to redo the file - just apply the "print curve" that
fits the image into the printer/paper/ink tonal space.  Then take a last
look at the image on screen knowing that because it is all in-gamut it will
be faithfully reproduced.  New ink/paper combo?  No problem.  For file
preparation (as opposed to RIP preparation) all you need to know is the
tonal range of the combo - paper white and dMax - and dial them into the
"print curve" -  by simply changing the two end points of an existing print
curve (although you might like to tweak how the curve approaches the "knees"
of the tonal response of the ink/paper combo).

So the workflow becomes: 1. Get the image looking nice on screen using the
full gamut available as usual - save as file copy.  2. Apply a print curve
which specifically takes into account the tonal range of the ink/paper combo
you intend to print to (these could simply be stored somewhere) - you can
physically see the end points in the tonal range, the midpoint and all in
between. Now the image on screen is all in-gamut and the tonal relationships
are exactly how they will print. 3.  Make any last minute, image specific
adjustments - these would be simple tweaks to the print curve. 4. Print.
> 
> Interesting stuff, but it's too easy to get hung up in the numbers and ignore
> the aesthetics of the image.
> 

I agree.  But it would be easier if we got what we were looking for when we
push a button or shifted a curve.  That is, full logical transparency.

Cheers

Steve

Hello Steve,

>The immediate answer to your question at the bottom is that there 
>is nothing you can do about it because you (much like Paul) can't 
>get inside the Epson driver...

Ok, understood, thanks.   Very interesting discussion.

Regards,
Clayton


Info on black and white digital printing at    
http://www.cjcom.net/digiprnarts.htm

Steve,

>...  When you ask your question do you simply
>show a big 50% step on screen and print (no other steps)?  ...

Of course, a single 50% patch would be rather meaningless.  But it's a place
to start.  The major "problem" is actually the way the monitors compress the
darkest few steps to the point that, in my view, it's just wasting our
limited grayscale.  If we had 16 bits through the entire process, that might
not be a serious issue, but with only 256 steps per channel in the final
step of the typical workflow, I think we need to utilize those that are near
the bottom of the range.  So, I use what I consider a more "linear" curve
than the monitors display unless other than the usual calibration is uses.


>> Most of the curves require that a grayscale file be converted to 
>>Adobe RGB first.  Then the RGB curves map to the CMY inks, 
>>black being generated by a combination of the curves.  
>>So, the RGB curves provide input-output relationships that 
>>allow me to specify the density of the image at each point.
>>It's just using Photoshop curves and the driver controls or built-in
>>characteristics (including cross-overs) to do most of what RIPs do.

>Yep.  I was wondering how mid grey (50% or 128) was modified.  
>I haven't seen any of your curves.

Download one of them and take a look.  See
http://home1.gte.net/res09aij/index.htm for my general index.  Of course,
you'll need to be familiar with the inkset densities for the curves to make
sense.

> How 50% maps to your print result is a function of
>(a) your curves and (b) the transfer function buried in the 
>Epson driver

All RIPs have a transfer function buried in them at some level.  I don't see
any one telling the  printer in machine code which dots to put where.  The
Epson driver is a RIP -- but with some "hard-wired" cross-overs (which are
excellent and useful if consistent with the desired results).

>even more complicated by the fact that the Epson driver is 
>expecting totally different inks.  So not transparent like a RIP ...

The Photoshop controls are more limited than a good RIP, but the differences
are a matter of degree.  There isn't that much difference.  The only place
I've been able to see a qualitative difference is where one needs to get
control of individual jets and avoid the built-in driver cross-overs.

The ink differences are largely taken care of in the inkset design, where I
work backwards from the printer and drive to the ink densities.  I prefer to
work with printers designed for pigments, because then the differences
between the OEM design assumptions and what I have available are minor.
It's amazing the dye printers work as well as they do.   But, again, since I
do the inkset design work also, I fit the 2 together.

The problems I have here are, for example, with what I'm doing now.  I'm
trying to work with an existing inkset -- the UT-FSN -- and make an inkset
that will print top notch matte and gloss prints on my 7500 and other large
format printers of that generation without the need to change the black ink.
The FS ink densities were never intended for this.  However, I've found that
only one new ink will be needed -- a medium gray that is denser than the
existing medium gray FS ink.  However, even here, where I'm not sure there
will be enough volume for MIS to be interested in making the inkset, I find
a way to easily mix the needed ink from exiting stock (in this case UT-FSN-M
and EZ-N).  But, so far, I'm finding the printer controls I have with the
Epson drive and Photoshop appear to give me what I need to do the job.

I'm not intending to restrict myself to the Epson driver.  When reasonably
priced RIPs can improve the situation, I'll use them.


> ...
>So the workflow becomes: 1. Get the image looking nice on screen ...
> save as file copy.  2. Apply a print curve which specifically takes 
>into account the tonal range of the ink/paper combo ...

That's it.

> ... 3.  Make any last minute, image specific adjustments - ...

I'd do this in #2. However, in reality, I always assume that I need to print
some draft prints and look at hard copy.  Not infrequently I make a slightly
modified curve for the specific print, saving it with the information I need
to identify it as a printing file for a specific paper, size, etc.  I just
don't think any monitor can take the place of viewing the print on paper. 


>...But it would be easier if we got what we were looking for when we
>push a button or shifted a curve.  That is, full logical transparency.

But that is where the skill and artistry comes in. 

Paul
www.PaulRoark.com

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark"
<paul.roark@v...> wrote:
>...The major "problem" is actually the way the monitors compress the
> darkest few steps to the point that, in my view, it's just wasting our
> limited grayscale.

I realize we all spend too much money on all this stuff, and I hate to
suggest more. But considering what we spend on materials over the
months I really think good monitor calibration has become a necessity
for anyone doing critical imaging work. With the latest generation of
EyeOne and Colorvision products, I can see the difference between
level 0 and level 1, between level 1 and level 2, etc..
I hear the Monaco offering is very good, and though I've had a few
problems with it, the new basICColor display is reportedly excellent.
These days good monitor calibration can be had for $200 or under if
you shop around, upgrades tend to be free for quite a while. It is
possible to overcome this problem.

It is also possible to characterize any output system, including one
using RGB curves and the Epson driver, with a preview profile that
will soft proof quite well.

...

> I'm not intending to restrict myself to the Epson driver.  When
reasonably
> priced RIPs can improve the situation, I'll use them.

That day has been here for a while. QTR is ridiculously reasonable,
and IJC/OPM is also very reasonable.
I'm not suggestion you abandon the Epson driver or change anything you
are doing, but I think you would be quite pleased with what you can do
with these tools once you start playing with them.

There is a lack of consensus about what "linear" is, and what middle
gray is. Other than that the issues addressed in this thread,
regarding display characteristics, workingspace, output
characteristics, their differences, overcoming them one way or
another, can be dealt with. Usually it involves color management in
some way, gotta get on top of that.

Tyler

Tyler,

>--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark"
><paul.roark@v...> wrote:
>>...The major "problem" is actually the way the monitors compress the
>> darkest few steps to the point that, in my view, it's just wasting our
>> limited grayscale.

>... I really think good monitor calibration has become a necessity

I have the SpyderPro2.  

> With the latest generation of
>EyeOne and Colorvision products, I can see the difference between
>level 0 and level 1, between level 1 and level 2, etc..

Maybe I set mine up wrong.  There is a step, I believe where you're supposed
to set it so that you can barely see the difference between 2 dark patches.
I've been thinking I may have overdone the "barely."

Paul
www.PaulRoark.com

Hi Tyler


> From: Tyler Boley <tyler@...>



> With the latest generation of
> EyeOne and Colorvision products, I can see the difference between
> level 0 and level 1, between level 1 and level 2, etc..

When you say Level 0, 1, 2 etc, what scale are you referring to?


> 
>> I'm not intending to restrict myself to the Epson driver.  When
> reasonably
>> priced RIPs can improve the situation, I'll use them.
> 
> That day has been here for a while. QTR is ridiculously reasonable,
> and IJC/OPM is also very reasonable.

Yes could not agree more.

> There is a lack of consensus about what "linear" is,

Not meaning to not pick but I would have said that "linear" is understood,
but there can be debate as to at which gamma and between which points.  I
would argue we should be linear from dMin to dMax on which I think we all
agree.  The question is where in the scale of 0 to 1 dMin and dMax should be
related to the image file's pixel values.

> and what middle
> gray is. 

This again is a question of gamma, no? In pixel terms, 0 is zero and 1 is
one.  The question is how the rate of change is managed in between.

> Other than that the issues addressed in this thread,
> regarding display characteristics, workingspace, output
> characteristics, their differences, overcoming them one way or
> another, can be dealt with.
> Usually it involves color management in
> some way, gotta get on top of that.
> 

Yes they can be "dealt with".  But it is interesting that they persist to
begin with.  We are in the unusual position of having a very narrow gamut to
work in.  Our work is largely done in a straight single dimension (only
toning takes us into the colour world).  The ultimate would, as you say, be
a colour managed world (without metamerism!) but that seems to be a way
away.  Colour management developed to solve the problem of moving between
devices with different colour gamut, and sophisticated mechanisms for
dealing with different gammas and out of gamut colours were developed in
parallel (else a profile would be useless).  The funny thing is, in B&W we
have chosen to work between two different colour/tonal spaces without the
benefit of a translation tool (colorsync) when we could easily make the two
tonal spaces the same and not have the issue to begin with!


Steve

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Paul Roark"
<paul.roark@v...> wrote:
...
> I have the SpyderPro2.  
> 
> > With the latest generation of
> >EyeOne and Colorvision products, I can see the difference between
> >level 0 and level 1, between level 1 and level 2, etc..
> 
> Maybe I set mine up wrong.  There is a step, I believe where you're
supposed
> to set it so that you can barely see the difference between 2 dark
patches.
> I've been thinking I may have overdone the "barely."

Possibly. I find it maddening that hardware calibration depends on
some subjective steps. But I think it's because those settings are
very dependent on the user's particular environment, ambient light.
SpyderPro2 that you have is my current fav, the results I mention were
real. I would think the software would separate things out done there
even with a dark hardware setting, but since the device blocks out
ambient when reading, perhaps that setting is the key.
Tyler

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> Hi Tyler
> 
> 
> > From: Tyler Boley <tyler@t...>
> 
> 
> 
> > With the latest generation of
> > EyeOne and Colorvision products, I can see the difference between
> > level 0 and level 1, between level 1 and level 2, etc..
> 
> When you say Level 0, 1, 2 etc, what scale are you referring to?

Photoshop levels, 0 - 255.

...
> > There is a lack of consensus about what "linear" is,
> 
> Not meaning to not pick but I would have said that "linear" is
understood,
> but there can be debate as to at which gamma and between which points.

That's what I mean, not consensus about linear along what scale? Lab?
A grayscale space? Which one? RGB space? Which gamma? Density? What
dot gain?
And in fact it doesn't really matter, because if it's linear by some
standard, and I can characterize it and predict it, I can succeffuly
softproof and print to it.

...
> > Other than that the issues addressed in this thread,
> > regarding display characteristics, workingspace, output
> > characteristics, their differences, overcoming them one way or
> > another, can be dealt with.
> > Usually it involves color management in
> > some way, gotta get on top of that.
> > 
> 
> Yes they can be "dealt with".  But it is interesting that they
persist to
> begin with.

They have always persisted. Different B&W papers have difference
middle grays from the same neg even given the same highlight point and
shadow point. Film too. All devices, whether monitors, printers,
whatever, have their own characteristcs. Beyond that there are
manufacturing tolerances, monitor drift, etc..
I think it will always persist and dealing with it is part of what we do.

>...  We are in the unusual position of having a very narrow gamut to
> work in.  Our work is largely done in a straight single dimension (only
> toning takes us into the colour world).  The ultimate would, as you
say, be
> a colour managed world (without metamerism!) but that seems to be a way
> away.

Color management techniques are being used all the time, even with
monochromatic inks.

> Colour management developed to solve the problem of moving between
> devices with different colour gamut, and sophisticated mechanisms for
> dealing with different gammas and out of gamut colours were developed in
> parallel (else a profile would be useless).  The funny thing is, in
B&W we
> have chosen to work between two different colour/tonal spaces
without the
> benefit of a translation tool (colorsync) when we could easily make
the two
> tonal spaces the same and not have the issue to begin with!

Well, that's where we disagree.
Tyler

> From: Paul Roark <paul.roark@...>


> Of course, a single 50% patch would be rather meaningless.  But it's a place
> to start.  

I agree.  What I meant though is that it may be fairer to simply show them
your mid grey only.  As this is the only number you target this is the only
one that is fair to test.  With a dMax of 1.56 (from your 21-step-K156.tif)
your printer can't even print anything to the left of your 80 step!  So
asking someone to compare a step wedge on the screen either Adobe RGB or
Gray Gamma 2.2 (both gamma 2.2 workspaces) with the printed version is
guaranteed the outcome you are getting especially if they are influenced by
comparing steps in the darker end (we have better means to get closer to
pure white than pure black).

(Take your 100% step for example - pure black, K=100%, LAB = 0.  Even your
monitor can't reproduce this but it gets a darn sight closer than your
printer.  Your Xrite measures your monitor's luminosity at pixel value = 0
(LAB=0 etc) in order to profile the monitor.  Unfortunately I do not know to
access the figure it measures (nor for the value measured by Eye-One) - I am
sure someone can tell us how.  With the number in hand you can calculate its
density equivalent and compare it with 1.56.)

I you are showing someone a full step wedge - the only fair test is for them
to look at it on screen with a curve that compresses the image tonal range
to the 0-255 equivalents of 1.56 and 0.04, with the curve in between such
that the on screen densities are those that you intend.  For example, in a
2.2 workspace if it goes through 128/128 then you intend a 0.66 density for
your 50% step.   Just for a laugh do this:  pull up your step wedge image;
do a curve with the end input/output points of 0/49 and 255/243; passing
through 128/135; run the eyedropper over the 100, 50 and 0 steps and record
the LAB figures; and then calc the densities.  You will I believe get
roughly 1.56, 0.62 and 0.04.  Those three steps (on a well profiled monitor)
should now match the printed version of K156.tif (ok so the 50 is a fraction
off and I am sure you can fiddle for the right input/output combo that hits
the nail on the head!).  Fit all the other points and you get a look at the
complete transfer curve that is taking place in the print end of your
workflow.

> The major "problem" is actually the way the monitors compress the
> darkest few steps to the point that, in my view, it's just wasting our
> limited grayscale.

I think this is a different kettle of fish entirely - much like Tyler's
reference to the question of what OUGHT to be mid grey or what OUGHT to be
the right workspace.  This is WAY beyond my knowledge and not something I
intend to tackle. I have no clue. I am currently very happy with Adobe
RGB/Gray Gamma 2.2.

I don't care which is chosen - what I do find ironic though is that people
set a workspace of gray gamma but linearize to a different workspace such as
LAB.  At a minimum they OUGHT to be the same to remove one layer of transfer
complexity when we are not working in a colour synchronised workflow (that
would manage this complexity for us).  I would love someone to give me a
credible explanation as to why they are different?


> Download one of them and take a look.  See
> http://home1.gte.net/res09aij/index.htm for my general index.  Of course,
> you'll need to be familiar with the inkset densities for the curves to make
> sense.

I'll definitely take a look.

> All RIPs have a transfer function buried in them at some level.  I don't see
> any one telling the  printer in machine code which dots to put where.  The
> Epson driver is a RIP -- but with some "hard-wired" cross-overs (which are
> excellent and useful if consistent with the desired results).

Yep.  But a programme like QTR does tell the printer what density (in
percentage ink terms) to lay down where and this is quite "open".  This is
defined in the code associated with the linearization.  QTR does not go so
far as to allow a user to define the type of linearization though - that
really would be quite a masterpiece.

 
> The Photoshop controls are more limited than a good RIP, but the differences
> are a matter of degree.  There isn't that much difference.  The only place
> I've been able to see a qualitative difference is where one needs to get
> control of individual jets and avoid the built-in driver cross-overs.
> 
> The ink differences are largely taken care of in the inkset design, where I
> work backwards from the printer and drive to the ink densities.  I prefer to
> work with printers designed for pigments, because then the differences
> between the OEM design assumptions and what I have available are minor.
> It's amazing the dye printers work as well as they do.   But, again, since I
> do the inkset design work also, I fit the 2 together.
> 
> The problems I have here are, for example, with what I'm doing now.  I'm
> trying to work with an existing inkset -- the UT-FSN -- and make an inkset
> that will print top notch matte and gloss prints on my 7500 and other large
> format printers of that generation without the need to change the black ink.
> The FS ink densities were never intended for this.  However, I've found that
> only one new ink will be needed -- a medium gray that is denser than the
> existing medium gray FS ink.  However, even here, where I'm not sure there
> will be enough volume for MIS to be interested in making the inkset, I find
> a way to easily mix the needed ink from exiting stock (in this case UT-FSN-M
> and EZ-N).  But, so far, I'm finding the printer controls I have with the
> Epson drive and Photoshop appear to give me what I need to do the job.
> 
> I'm not intending to restrict myself to the Epson driver.  When reasonably
> priced RIPs can improve the situation, I'll use them.
> 
I can't even begin to think about fussing with ink design!  Hopefully you
won't stop doing what you do.

>> ...
>> So the workflow becomes: 1. Get the image looking nice on screen ...
>> save as file copy.  2. Apply a print curve which specifically takes
>> into account the tonal range of the ink/paper combo ...
> 
> That's it.
> 
>> ... 3.  Make any last minute, image specific adjustments - ...
> 
> I'd do this in #2. However, in reality, I always assume that I need to print
> some draft prints and look at hard copy.  Not infrequently I make a slightly
> modified curve for the specific print, saving it with the information I need
> to identify it as a printing file for a specific paper, size, etc.  I just
> don't think any monitor can take the place of viewing the print on paper.


Completely agree.  A tweak would be to the same curve but would affect
points within the tonal range of the printer only. My proposed workflow
simply dials in the end points of the paper/ink combo, initially without
moving "mid grey" (which I am happy to have be 0.5 in gray gamma 2.2) and a
smoothing of the image compression with a nice S curve. Tweaks can be
infinite but tweaks at this stage relate to the effect of tonal compression
- the fact that I can't print the full image as I would otherwise like (I
can't print the tonal range of my monitor) - and largely likely in relation
to the knee points (highlights and deep shadows).

 
> 
>> ...But it would be easier if we got what we were looking for when we
>> push a button or shifted a curve.  That is, full logical transparency.
> 
> But that is where the skill and artistry comes in.

What I meant was the technical end.  You targeted 50% to a density of 0.61
yet it sits at 0.66 on screen and have explored the reason as to why people
have said it seems to print light.  What I meant was that it would be nice
to look at 0.66 and have it print 0.66.  This was not meant to be a
substitute for the artistry associated with which part of the image is 0.66!

Cheers

Steve

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
...
> I am currently very happy with Adobe
> RGB/Gray Gamma 2.2.
> 
> I don't care which is chosen - what I do find ironic though is that
people
> set a workspace of gray gamma but linearize to a different workspace
such as
> LAB.  At a minimum they OUGHT to be the same to remove one layer of
transfer
> complexity when we are not working in a colour synchronised workflow
(that
> would manage this complexity for us).  I would love someone to give me a
> credible explanation as to why they are different?

Requirements of an optimum working/editing space are complex and
differ from "good" output linearization, or say, a monitor space. This
is one reason we have color management. There is a great deal of sense
in selecting LAB as a standard for output, it's based on years of
stufy on how humans see.
In some ways that decision makes more sense than why one may select a
particular working space, they just happened to be the ones that come
with Photoshop.
If you wanted to carry your ideas forward, it would be very easy to
make a custom gray space with the same gamma as LAB, or, for a Roarke
RGB workflow, use a custom gamma RGB space that matches that output's
gamma.



> ...QTR does not go so
> far as to allow a user to define the type of linearization though - that
> really would be quite a masterpiece.

Well, it's just going to cost you more. If I recall, OPM/IJC
linearizes to a user selectable choice of gammas 1.8 or 2.2 (someone
correct me). A user would have to report to you regarding whether or
not there is a good monitor match using the corresponding gray working
spaces.
StudioPrint is linearized to whatever the user selects. We linearize
to 20% dot gain, and use a 20% dot gain gray working space. While
monitor match is pretty good, soft proof is still much better.
Other users select a gamma based space, and adjust the target output
dot gain to suit, visually I assume.
The only way to properly display (to the degree you may be seeking),
on a monitor, a device/workflow/whatever is to characterize it and use
soft proof. I can even find fault with that, but it's miles ahead of
where we were before softproof.
Lastly, I have to come back to monitor calibration. If you would
prefer developers linearize their processes to the look of a generally
accepted working space on monitor....
...whose monitor?
Tyler

For those interested, more amazing info from the always amazing Bruce
Lindbloom-
http://www.brucelindbloom.com/index.html?BetaRGB.html

Interesting that gamma and LAB do not progress uniformly. So if you
really wanted a custom gray space that closely resembled LAB, you'd
have to do it with one based on dot gain (multiple curve points)
rather than gamma.
Tyler

Hi Tyler


> From: Tyler Boley <tyler@...>


> Requirements of an optimum working/editing space are complex and
> differ from "good" output linearization, or say, a monitor space. This
> is one reason we have color management.
> There is a great deal of sense
> in selecting LAB as a standard for output, it's based on years of
> stufy on how humans see.
> In some ways that decision makes more sense than why one may select a
> particular working space, they just happened to be the ones that come
> with Photoshop.

OK.  In the past when you guys debated or asked the question re to which
space you linearized I didn't understand the question let alone the answer
and so I didn't really follow the subject matter.  I guess I am still a
little puzzled though.  Everything I have read about CIELAB is that it is a
very broad colour space, encompassing Adobe RGB, SRGB et al, but that it is
not very "useful" for editing, principally because it is not as intuitive as
RGB and its broader gamut doesn't offer much incremental value. I am sure
this is contended!  It is useful of course as an intermediate space, used in
the background by PS when switching colour spaces but about the only widely
used use of LAB in editing that I have encountered is when sharpening, ie
sharpening the L channel because it has no colour info and hence can't
induce colour change when sharpening.

One can see the difference between LAB and gamma 2.2 on a step wedge by
assigning the two profiles to two step wedges and looking at the difference
and the differences can be expressed in density terms by converting the
figures shown in the info palette to their density equivalents.

For example, if Paul (or anyone else) wants to target a LAB mid point for
his curves then 50% needs to be LAB=50 or a density of 0.73, rather than
0.66 for gamma 2.2 or the current 0.61.  This would also match a grey card's
18% reflectance.

Your other post provided a link to Bruce Lindbloom's Beta RGB.  This is the
result of his search for an optimal working space.  It is interesting that
he chose a gamma of 2.2 for Beta RGB and for grey scale:

"I have previously analyzed the optimal gamma for the grayscale only (you
can  see this analysis [here]). This result was about 2.2 (actually either
2.1723 or 2.3243 depending  upon the error metric used).

For Beta RGB, I additionally performed a three-dimensional
analysis....[which] resulted in a gamma of 2.12. This was sufficiently close
to 2.2 that I did not feel a deviation from a "standard" 2.2 value was
warranted."

One can take this one of two ways: (A) working in 2.2 gamma is a good
compromise for visualizing LAB output or (B) there is not much to be gained
from linearizing to 2.2 gamma versus LAB.

EITHER way, the question still begs over WHAT RANGE the linearization
calculation should take place.  Note Bruce's charts all have an x-axis range
from 0 to 1 that he calls Input Value ie this is what I have been calling
(from Norman's nomenclature) normalised pixel value.  When we linearize (to
LAB) with QTR we do so from dMin to dMax over the full range of 0 to 1.  Yet
for, say EEM, the printer can only reproduce pixel values from 0.18 to 0.95.
As a result, the linearization does not follow the LAB curve shown on
Bruce's site but rather takes on a completely different curvature and mid
point.  If instead we linearized to LAB over the range of pixel values that
the printer can reproduce, ie from dMin (paper white/ink=0) @ 0.95 to dMax
(ink black) @ 0.18, then we would get linearization that meets what we
wanted - the LAB curve between the values at which the printer can register
tonal change (can I call this "dynamic range"?).

(Also note that we would still need to fill the slots for the missing values
on either side of the range. If these were left at no ink and full ink
respectively then the curve would take on the form of a curve for film or
photographic paper.  A printer loaded with ink is directly comparable to
these two other mediums.)

> If you wanted to carry your ideas forward, it would be very easy to
> make a custom gray space with the same gamma as LAB, or, for a Roarke
> RGB workflow, use a custom gamma RGB space that matches that output's
> gamma.

Or I could choose B above and linearize to gamma 2.2.  The question is how
much is gained from LAB.

In any case, I think the PRIMARY issue is the one that I outline above
(beginning "EITHER way").

> 
> 
> 
>> ...QTR does not go so
>> far as to allow a user to define the type of linearization though - that
>> really would be quite a masterpiece.
> 
> Well, it's just going to cost you more. If I recall, OPM/IJC
> linearizes to a user selectable choice of gammas 1.8 or 2.2 (someone
> correct me). A user would have to report to you regarding whether or
> not there is a good monitor match using the corresponding gray working
> spaces.
> StudioPrint is linearized to whatever the user selects. We linearize
> to 20% dot gain, and use a 20% dot gain gray working space. While
> monitor match is pretty good, soft proof is still much better.

With reference to my point above, do you linearize over 0 to 1 or over the
dynamic range for that curve?

> Other users select a gamma based space, and adjust the target output
> dot gain to suit, visually I assume.
> The only way to properly display (to the degree you may be seeking),
> on a monitor, a device/workflow/whatever is to characterize it and use
> soft proof. 

Or define it in curve format so that the transformation curve can be saved
and the transformed image can be saved.  Not I have been making a very big
simplifying assumption that we are primarily interested, when editing, in
tonal rendition and not hue (largely because I think this is practice and
secondly we can only edit hue by writing a different curve).

> I can even find fault with that, but it's miles ahead of
> where we were before softproof.
> Lastly, I have to come back to monitor calibration. If you would
> prefer developers linearize their processes to the look of a generally
> accepted working space on monitor....
> ...whose monitor?

It is not linearizing to monitor per se, eg if linearization to LAB is
deemed critical and 2.2 is considered a satisfactory compromise for editing
then I could perhaps live with the difference (because it is so small) only
if my primary issue is suitably resolved.  It is getting the linearization
intended: a linearization to x (LAB, 2.2 or whatever) over the range of
values within which the printer can record changes tonal change, ie
linearization over the dynamic range of the printer.

Cheers

Steve

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
...
> > Requirements of an optimum working/editing space are complex and
> > differ from "good" output linearization, or say, a monitor space. ...
> > There is a great deal of sense
> > in selecting LAB as a standard for output, it's based on years of
> > stufy on how humans see.
...
>...Everything I have read about CIELAB is that it is a
> very broad colour space, encompassing Adobe RGB, SRGB et al, but
that it is
> not very "useful" for editing, principally because it is not as
intuitive as
> RGB and its broader gamut doesn't offer much incremental value. I am
sure
> this is contended!

Steve, my wording above was perhaps confusing. I did not mean to imply
LAB makes sense as a working or editing space, but as an output
standard for linearization. 

...
> With reference to my point above, do you linearize over 0 to 1 or
over the
> dynamic range for that curve?

I still don't see the logic in your previous assertions. an input
value of 0 will always map to "no ink", paper white. It's density will
always be determined by the particular paper. 1 (one) will always be
the dmax capable from the particular hardware/workflow/materials.
There are no input values "outside" that range. I don't see how any
other approach can be useful. Put in a different paper, less white or
with a coating that can't print as black, and everything changes. But
I still want the full linearized range between, so why would I clip
info or whatever?
I'm not challenging what you have been saying, I've just not carefully
followed it due to brain constraints on my end.
StudioPrint is linearizing between paper white and ink black, though I
can select where that black point is based on what the readings are
telling me (there may be a better black point than max ink load).
But I still want to send the RIP ALL the values of the file.

...
> It is not linearizing to monitor per se, eg if linearization to LAB is
> deemed critical and 2.2 is considered a satisfactory compromise for
editing
> then I could perhaps live with the difference (because it is so
small) only
> if my primary issue is suitably resolved.  It is getting the
linearization
> intended: a linearization to x (LAB, 2.2 or whatever) over the range of
> values within which the printer can record changes tonal change, ie
> linearization over the dynamic range of the printer.

As far as I can tell, unless we are talking in circles or I'm not
paying attention, that's what we are doing. That's what color output
profiles are doing, and QTR linearization, Paul's RGB curves, etc. are
doing. Linearization is always accomplished between the end points of
the output dynamic range.
The remaining issue of this thread, which you raise and has always
been unresolved, is a universally accepted standard to which we all
linearize B&W. But the side issiue I have been pushing, is that with
good color management and calibration practice, it's not a big
problem. Because once a linearized (to whatever) device is well
characterized, any file (assuming we know what it is supposed to look
like, iow tagged) can be made to print on it as expected given
reasonable expectations.
Sorry if I'm missing the point, or telling you things you already know.
Gotta get to work around here.
Tyler

Tyler

Ever narrowing circles of misunderstanding! We are getting closer - I think.
I wish I we had a white board - I think we would be done in about 10
seconds.


> From: Tyler Boley <tyler@...>



> Steve, my wording above was perhaps confusing. I did not mean to imply
> LAB makes sense as a working or editing space, but as an output
> standard for linearization.
> 

I understood you.  I guess I was raising the counter question that if there
is little difference in grey scale between 2.2 gamma and LAB (see Bruce's
curves) then what is gained by output at LAB?  But as I noted later in my
post, as the error rate between 2.2 gamma and LAB is low, I could tolerate
the difference if we solve the issue below:

> ...
>> With reference to my point above, do you linearize over 0 to 1 or
> over the
>> dynamic range for that curve?
> 
> I still don't see the logic in your previous assertions. an input
> value of 0 will always map to "no ink", paper white. It's density will
> always be determined by the particular paper. 1 (one) will always be
> the dmax capable from the particular hardware/workflow/materials.
> There are no input values "outside" that range. I don't see how any
> other approach can be useful. Put in a different paper, less white or
> with a coating that can't print as black, and everything changes. But
> I still want the full linearized range between, so why would I clip
> info or whatever?
> I'm not challenging what you have been saying, I've just not carefully
> followed it due to brain constraints on my end.
> StudioPrint is linearizing between paper white and ink black, though I
> can select where that black point is based on what the readings are
> telling me (there may be a better black point than max ink load).
> But I still want to send the RIP ALL the values of the file.
> 

OK let me try to explain what I am thinking.

Let's assume we do our step wedges like Paul does: 100% black (pixel value
0) on the left, 0% black ie white (pixel value 1) on the right.

First of all, I suspect we can agree that we both want to use the full range
of the printer and I think we can also agree that since the tonal range of
the printer is less than the tonal range of the image file (assuming the
image has been adjusted to fill or spread pixel values from 0 to 1, either
naturally, with a curve or with a levels adjustment) there must be some
compression of tonal range - either by the RIP or before it gets to the RIP.
Let's leave which to one side for now! Let us also agree that we don't want
any clipping.  So we have a necessary compression from perfect black (pixel
value = 0) to printer dMax and from pure white (pixel value = 1) to paper
white, and some function in between.

Do you agree that we can measure and test the results of our linearization
ie we have an empirical test as to whether we have done things right?  This
can be done by printing another step wedge with linearization "in place"
measuring the densities, calculating their luminosity equivalents, plotting
log10(luminance), ie -Density, against log10(pixel value), and comparing
this versus the same figures for the gamma 2.2 space.  The two graphs should
overlap as straight lines for the range of log10(pixel value) which are
within the tonal range of the printer.  If they do not then we have not then
we have not linearized to our chosen space.

The target values for gamma 2.2 are in 11 steps:

Norm. Pixel Val   log10(pixel value)  log10(luminance)
0.0     -infinity   -infinity
0.1     -1.00    -2.20
0.2     -0.70   -1.54
0.3     -0.52   -1.15
0.4     -0.40   -0.88
0.5     -0.30   -0.66
0.6     -0.22   -0.49
0.7     -0.15   -0.34
0.8     -0.10   -0.21
0.9     -0.05   -0.10
1.0      0.00    0.00


The log10(luminance) or -Density figures for LAB would, I believe, be
-infinity, -1.95, -1.52, -1.21, -0.95, -0.73, -0.55, -0.39, -0.25, -0.12,
0.00.

Now unless I am mistaken, a linearized RIP like QTR when it receives a
normalised pixel of 0 puts down max ink and gets dMax, around 1.68 for EEM,
and when it gets a normalised pixel value of 1 it puts down zero ink and
gets dMin (paper white), around 0.04 for EEM.  Fine, but what about points
in between?  Let's look at normalised pixel value = 0.1 (25.5 in 8 bit).
Gamma 2.2 wants 2.20 and LAB wants 1.95 but the max the printer can produce
is 1.68. I believe QTR would give it even less than 1.68. I think we can
already see that our empirical test will fail.  There will be no overlapping
of the curves and they will not necessarily cross at 0.5.  Put another way,
the have a completely different gamma.  It may be linear (I haven't tested
it) but it isn't gamma 2.2 and it isn't LAB.

If on the other hand, I recognised that the printer can't begin to record
changes in tone until dMin and that this equates to our linerization target
norm. pixel value equivalent of just over 0.9 and that it stops recording
changes in tone at dMax and that this equates to our linearization target
norm. pixel value of just under 0.20 and I put dMin and dMax in these places
and linearized between them then I would have a solid overlap from dMin to
dMax in my empirical test chart.  I would have linearized to my target.
Outside of this range my printer can't register tonal range but within it I
have a rate of change of values consistent with gamma 2.2 or LAB, whichever
I chose.

(As an aside, what if I had a photographic paper which was as white as EEM
and could only record the same dMax as EEM and a contrast of 2.2, how would
Kodak plot it's "characteristic curve"?  It would begin flat at a density of
0.04 then turn upwards at a linear slope until it hits 1.68 reflection
density and turn flat again. The horizontal axis LOG Exposure is equivalent
to LOG normalised pixel Value.  Only the chart in the second case has the
same profile as that which would be drawn by Kodak.)

So putting off to one side for the moment the issue of editing in one space
and linearizing to another, I do not see how you can linearize to LAB or
gamma 2.2 except in the manner I have described.  You linearize I guess but
not the way you intend to.  And if LAB more closely matches the way the "eye
sees" then I would want to be sure that I matched it. Starting at the mid
and moving left seeing increasingly darker shades at the correct rate of
change (and vice versa to the right).  If I linearize the way I am
suggesting and I used LAB, I also get my Kodak grey card reading for all
pixels at the mid point of 0.5 (K=50%, LAB=50) if I read their density in
the final print.

I am really not sure that I can explain myself more clearly.  If you believe
in LAB then you want to linearize to LAB.  LAB says that if I have a 20%
change from 50 to 60 in my range I get a defined change in tone.  As you get
better paper white and better inks then the range around LAB=50 gets wider -
we reach further out on our step wedge ALWAYS AT THE SAME RATE AS LAB...not
some other rate of change.

I hope this helps and would welcome any comments

Steve

Just one more thought for the evening.  If QTR or IJC/OPM linearizes LAB
values from (0, 0.04) to (1, 1.68) for EEM, as an example, then I believe
this function is defined as y = -0.04 + 1.64x where x=log10(normalised pixel
value) = -Density. If I am not mistaken this is a gamma of 1.64.  This also
means 50% grey is printed with a density of 0.5337.  This is much lighter
than what we want.  A 60% step (norm. pixel value 0.4) prints at 0.6926.  So
a step from 50% to 60% was a change in density of 0.16.  Yet LAB would
prescribe a change of 0.73-0.55=0.18.  So if I wanted to print a simple
picture of 2 squares, one 50% grey and the other 60% grey this curve would
not print them properly, even though they are well within the tonal range of
the printer.

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Mon, 06 Dec 2004 21:17:18 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Tyler
> 
> Ever narrowing circles of misunderstanding! We are getting closer - I think.
> I wish I we had a white board - I think we would be done in about 10
> seconds.
> 
> 
>> From: Tyler Boley <tyler@...>
> 
> 
> 
>> Steve, my wording above was perhaps confusing. I did not mean to imply
>> LAB makes sense as a working or editing space, but as an output
>> standard for linearization.
>> 
> 
> I understood you.  I guess I was raising the counter question that if there
> is little difference in grey scale between 2.2 gamma and LAB (see Bruce's
> curves) then what is gained by output at LAB?  But as I noted later in my
> post, as the error rate between 2.2 gamma and LAB is low, I could tolerate
> the difference if we solve the issue below:
> 
>> ...
>>> With reference to my point above, do you linearize over 0 to 1 or
>> over the
>>> dynamic range for that curve?
>> 
>> I still don't see the logic in your previous assertions. an input
>> value of 0 will always map to "no ink", paper white. It's density will
>> always be determined by the particular paper. 1 (one) will always be
>> the dmax capable from the particular hardware/workflow/materials.
>> There are no input values "outside" that range. I don't see how any
>> other approach can be useful. Put in a different paper, less white or
>> with a coating that can't print as black, and everything changes. But
>> I still want the full linearized range between, so why would I clip
>> info or whatever?
>> I'm not challenging what you have been saying, I've just not carefully
>> followed it due to brain constraints on my end.
>> StudioPrint is linearizing between paper white and ink black, though I
>> can select where that black point is based on what the readings are
>> telling me (there may be a better black point than max ink load).
>> But I still want to send the RIP ALL the values of the file.
>> 
> 
> OK let me try to explain what I am thinking.
> 
> Let's assume we do our step wedges like Paul does: 100% black (pixel value
> 0) on the left, 0% black ie white (pixel value 1) on the right.
> 
> First of all, I suspect we can agree that we both want to use the full range
> of the printer and I think we can also agree that since the tonal range of
> the printer is less than the tonal range of the image file (assuming the
> image has been adjusted to fill or spread pixel values from 0 to 1, either
> naturally, with a curve or with a levels adjustment) there must be some
> compression of tonal range - either by the RIP or before it gets to the RIP.
> Let's leave which to one side for now! Let us also agree that we don't want
> any clipping.  So we have a necessary compression from perfect black (pixel
> value = 0) to printer dMax and from pure white (pixel value = 1) to paper
> white, and some function in between.
> 
> Do you agree that we can measure and test the results of our linearization
> ie we have an empirical test as to whether we have done things right?  This
> can be done by printing another step wedge with linearization "in place"
> measuring the densities, calculating their luminosity equivalents, plotting
> log10(luminance), ie -Density, against log10(pixel value), and comparing
> this versus the same figures for the gamma 2.2 space.  The two graphs should
> overlap as straight lines for the range of log10(pixel value) which are
> within the tonal range of the printer.  If they do not then we have not then
> we have not linearized to our chosen space.
> 
> The target values for gamma 2.2 are in 11 steps:
> 
> Norm. Pixel Val   log10(pixel value)  log10(luminance)
> 0.0     -infinity   -infinity
> 0.1     -1.00    -2.20
> 0.2     -0.70   -1.54
> 0.3     -0.52   -1.15
> 0.4     -0.40   -0.88
> 0.5     -0.30   -0.66
> 0.6     -0.22   -0.49
> 0.7     -0.15   -0.34
> 0.8     -0.10   -0.21
> 0.9     -0.05   -0.10
> 1.0      0.00    0.00
> 
> 
> The log10(luminance) or -Density figures for LAB would, I believe, be
> -infinity, -1.95, -1.52, -1.21, -0.95, -0.73, -0.55, -0.39, -0.25, -0.12,
> 0.00.
> 
> Now unless I am mistaken, a linearized RIP like QTR when it receives a
> normalised pixel of 0 puts down max ink and gets dMax, around 1.68 for EEM,
> and when it gets a normalised pixel value of 1 it puts down zero ink and
> gets dMin (paper white), around 0.04 for EEM.  Fine, but what about points
> in between?  Let's look at normalised pixel value = 0.1 (25.5 in 8 bit).
> Gamma 2.2 wants 2.20 and LAB wants 1.95 but the max the printer can produce
> is 1.68. I believe QTR would give it even less than 1.68. I think we can
> already see that our empirical test will fail.  There will be no overlapping
> of the curves and they will not necessarily cross at 0.5.  Put another way,
> the have a completely different gamma.  It may be linear (I haven't tested
> it) but it isn't gamma 2.2 and it isn't LAB.
> 
> If on the other hand, I recognised that the printer can't begin to record
> changes in tone until dMin and that this equates to our linerization target
> norm. pixel value equivalent of just over 0.9 and that it stops recording
> changes in tone at dMax and that this equates to our linearization target
> norm. pixel value of just under 0.20 and I put dMin and dMax in these places
> and linearized between them then I would have a solid overlap from dMin to
> dMax in my empirical test chart.  I would have linearized to my target.
> Outside of this range my printer can't register tonal range but within it I
> have a rate of change of values consistent with gamma 2.2 or LAB, whichever
> I chose.
> 
> (As an aside, what if I had a photographic paper which was as white as EEM
> and could only record the same dMax as EEM and a contrast of 2.2, how would
> Kodak plot it's "characteristic curve"?  It would begin flat at a density of
> 0.04 then turn upwards at a linear slope until it hits 1.68 reflection
> density and turn flat again. The horizontal axis LOG Exposure is equivalent
> to LOG normalised pixel Value.  Only the chart in the second case has the
> same profile as that which would be drawn by Kodak.)
> 
> So putting off to one side for the moment the issue of editing in one space
> and linearizing to another, I do not see how you can linearize to LAB or
> gamma 2.2 except in the manner I have described.  You linearize I guess but
> not the way you intend to.  And if LAB more closely matches the way the "eye
> sees" then I would want to be sure that I matched it. Starting at the mid
> and moving left seeing increasingly darker shades at the correct rate of
> change (and vice versa to the right).  If I linearize the way I am
> suggesting and I used LAB, I also get my Kodak grey card reading for all
> pixels at the mid point of 0.5 (K=50%, LAB=50) if I read their density in
> the final print.
> 
> I am really not sure that I can explain myself more clearly.  If you believe
> in LAB then you want to linearize to LAB.  LAB says that if I have a 20%
> change from 50 to 60 in my range I get a defined change in tone.  As you get
> better paper white and better inks then the range around LAB=50 gets wider -
> we reach further out on our step wedge ALWAYS AT THE SAME RATE AS LAB...not
> some other rate of change.
> 
> I hope this helps and would welcome any comments
> 
> Steve
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
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> 
>  
> 
> 
>

Whoops.  I have got this wrong!! My x-axis is log10(norm pixel value) not 0
to 1. 

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Mon, 06 Dec 2004 23:33:36 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Just one more thought for the evening.  If QTR or IJC/OPM linearizes LAB
> values from (0, 0.04) to (1, 1.68) for EEM, as an example, then I believe
> this function is defined as y = -0.04 + 1.64x where x=log10(normalised pixel
> value) = -Density. If I am not mistaken this is a gamma of 1.64.  This also
> means 50% grey is printed with a density of 0.5337.  This is much lighter
> than what we want.  A 60% step (norm. pixel value 0.4) prints at 0.6926.  So
> a step from 50% to 60% was a change in density of 0.16.  Yet LAB would
> prescribe a change of 0.73-0.55=0.18.  So if I wanted to print a simple
> picture of 2 squares, one 50% grey and the other 60% grey this curve would
> not print them properly, even though they are well within the tonal range of
> the printer.
> 
> 
>> From: Steve Kale <stevekale@...>
>> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Date: Mon, 06 Dec 2004 21:17:18 +0000
>> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
>> Subject: Re: [Digital BW] Tonal range and linearization
>> 
>> 
>> Tyler
>> 
>> Ever narrowing circles of misunderstanding! We are getting closer - I think.
>> I wish I we had a white board - I think we would be done in about 10
>> seconds.
>> 
>> 
>>> From: Tyler Boley <tyler@...>
>> 
>> 
>> 
>>> Steve, my wording above was perhaps confusing. I did not mean to imply
>>> LAB makes sense as a working or editing space, but as an output
>>> standard for linearization.
>>> 
>> 
>> I understood you.  I guess I was raising the counter question that if there
>> is little difference in grey scale between 2.2 gamma and LAB (see Bruce's
>> curves) then what is gained by output at LAB?  But as I noted later in my
>> post, as the error rate between 2.2 gamma and LAB is low, I could tolerate
>> the difference if we solve the issue below:
>> 
>>> ...
>>>> With reference to my point above, do you linearize over 0 to 1 or
>>> over the
>>>> dynamic range for that curve?
>>> 
>>> I still don't see the logic in your previous assertions. an input
>>> value of 0 will always map to "no ink", paper white. It's density will
>>> always be determined by the particular paper. 1 (one) will always be
>>> the dmax capable from the particular hardware/workflow/materials.
>>> There are no input values "outside" that range. I don't see how any
>>> other approach can be useful. Put in a different paper, less white or
>>> with a coating that can't print as black, and everything changes. But
>>> I still want the full linearized range between, so why would I clip
>>> info or whatever?
>>> I'm not challenging what you have been saying, I've just not carefully
>>> followed it due to brain constraints on my end.
>>> StudioPrint is linearizing between paper white and ink black, though I
>>> can select where that black point is based on what the readings are
>>> telling me (there may be a better black point than max ink load).
>>> But I still want to send the RIP ALL the values of the file.
>>> 
>> 
>> OK let me try to explain what I am thinking.
>> 
>> Let's assume we do our step wedges like Paul does: 100% black (pixel value
>> 0) on the left, 0% black ie white (pixel value 1) on the right.
>> 
>> First of all, I suspect we can agree that we both want to use the full range
>> of the printer and I think we can also agree that since the tonal range of
>> the printer is less than the tonal range of the image file (assuming the
>> image has been adjusted to fill or spread pixel values from 0 to 1, either
>> naturally, with a curve or with a levels adjustment) there must be some
>> compression of tonal range - either by the RIP or before it gets to the RIP.
>> Let's leave which to one side for now! Let us also agree that we don't want
>> any clipping.  So we have a necessary compression from perfect black (pixel
>> value = 0) to printer dMax and from pure white (pixel value = 1) to paper
>> white, and some function in between.
>> 
>> Do you agree that we can measure and test the results of our linearization
>> ie we have an empirical test as to whether we have done things right?  This
>> can be done by printing another step wedge with linearization "in place"
>> measuring the densities, calculating their luminosity equivalents, plotting
>> log10(luminance), ie -Density, against log10(pixel value), and comparing
>> this versus the same figures for the gamma 2.2 space.  The two graphs should
>> overlap as straight lines for the range of log10(pixel value) which are
>> within the tonal range of the printer.  If they do not then we have not then
>> we have not linearized to our chosen space.
>> 
>> The target values for gamma 2.2 are in 11 steps:
>> 
>> Norm. Pixel Val   log10(pixel value)  log10(luminance)
>> 0.0     -infinity   -infinity
>> 0.1     -1.00    -2.20
>> 0.2     -0.70   -1.54
>> 0.3     -0.52   -1.15
>> 0.4     -0.40   -0.88
>> 0.5     -0.30   -0.66
>> 0.6     -0.22   -0.49
>> 0.7     -0.15   -0.34
>> 0.8     -0.10   -0.21
>> 0.9     -0.05   -0.10
>> 1.0      0.00    0.00
>> 
>> 
>> The log10(luminance) or -Density figures for LAB would, I believe, be
>> -infinity, -1.95, -1.52, -1.21, -0.95, -0.73, -0.55, -0.39, -0.25, -0.12,
>> 0.00.
>> 
>> Now unless I am mistaken, a linearized RIP like QTR when it receives a
>> normalised pixel of 0 puts down max ink and gets dMax, around 1.68 for EEM,
>> and when it gets a normalised pixel value of 1 it puts down zero ink and
>> gets dMin (paper white), around 0.04 for EEM.  Fine, but what about points
>> in between?  Let's look at normalised pixel value = 0.1 (25.5 in 8 bit).
>> Gamma 2.2 wants 2.20 and LAB wants 1.95 but the max the printer can produce
>> is 1.68. I believe QTR would give it even less than 1.68. I think we can
>> already see that our empirical test will fail.  There will be no overlapping
>> of the curves and they will not necessarily cross at 0.5.  Put another way,
>> the have a completely different gamma.  It may be linear (I haven't tested
>> it) but it isn't gamma 2.2 and it isn't LAB.
>> 
>> If on the other hand, I recognised that the printer can't begin to record
>> changes in tone until dMin and that this equates to our linerization target
>> norm. pixel value equivalent of just over 0.9 and that it stops recording
>> changes in tone at dMax and that this equates to our linearization target
>> norm. pixel value of just under 0.20 and I put dMin and dMax in these places
>> and linearized between them then I would have a solid overlap from dMin to
>> dMax in my empirical test chart.  I would have linearized to my target.
>> Outside of this range my printer can't register tonal range but within it I
>> have a rate of change of values consistent with gamma 2.2 or LAB, whichever
>> I chose.
>> 
>> (As an aside, what if I had a photographic paper which was as white as EEM
>> and could only record the same dMax as EEM and a contrast of 2.2, how would
>> Kodak plot it's "characteristic curve"?  It would begin flat at a density of
>> 0.04 then turn upwards at a linear slope until it hits 1.68 reflection
>> density and turn flat again. The horizontal axis LOG Exposure is equivalent
>> to LOG normalised pixel Value.  Only the chart in the second case has the
>> same profile as that which would be drawn by Kodak.)
>> 
>> So putting off to one side for the moment the issue of editing in one space
>> and linearizing to another, I do not see how you can linearize to LAB or
>> gamma 2.2 except in the manner I have described.  You linearize I guess but
>> not the way you intend to.  And if LAB more closely matches the way the "eye
>> sees" then I would want to be sure that I matched it. Starting at the mid
>> and moving left seeing increasingly darker shades at the correct rate of
>> change (and vice versa to the right).  If I linearize the way I am
>> suggesting and I used LAB, I also get my Kodak grey card reading for all
>> pixels at the mid point of 0.5 (K=50%, LAB=50) if I read their density in
>> the final print.
>> 
>> I am really not sure that I can explain myself more clearly.  If you believe
>> in LAB then you want to linearize to LAB.  LAB says that if I have a 20%
>> change from 50 to 60 in my range I get a defined change in tone.  As you get
>> better paper white and better inks then the range around LAB=50 gets wider -
>> we reach further out on our step wedge ALWAYS AT THE SAME RATE AS LAB...not
>> some other rate of change.
>> 
>> I hope this helps and would welcome any comments
>> 
>> Steve
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> Please visit the Group Homepage to check the Files, and other resources as
>> they are often being updated.
>> 
>> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
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>> Yahoo! Groups Links
>> 
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>> 
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> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
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> unsubscribe, please edit your Membership preferences by visiting this same
> page.
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> Please follow these basic guidelines:
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> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
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> printing. Users who persistently make off-topic posts may be removed from the
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> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE �OWNER� AND
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> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
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> 
> 
>  
> 
> 
>

Whoops.  Sorry, I have got this wrong!! In a linearization, it is log10(norm
pixel value) versus log10(luminance) or -Density that should be linear. (Not
0 to 1 on the x-axis as I did below!) Gamma 1.8, 2.2, nor LAB  are linear
when normalised pixel values are plotted against density.

Now I am really intrigued as to how a programme like QTR or IJC/OPM does
this given the log10(0) is -infinity.

What do you guys linearize?

(Boy, the below really was a piece of garbage thinking!)

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Mon, 06 Dec 2004 23:33:36 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Just one more thought for the evening.  If QTR or IJC/OPM linearizes LAB
> values from (0, 0.04) to (1, 1.68) for EEM, as an example, then I believe
> this function is defined as y = -0.04 + 1.64x where x=log10(normalised pixel
> value) = -Density. If I am not mistaken this is a gamma of 1.64.  This also
> means 50% grey is printed with a density of 0.5337.  This is much lighter
> than what we want.  A 60% step (norm. pixel value 0.4) prints at 0.6926.  So
> a step from 50% to 60% was a change in density of 0.16.  Yet LAB would
> prescribe a change of 0.73-0.55=0.18.  So if I wanted to print a simple
> picture of 2 squares, one 50% grey and the other 60% grey this curve would
> not print them properly, even though they are well within the tonal range of
> the printer.
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
...
> I understood you.  I guess I was raising the counter question that
if there
> is little difference in grey scale between 2.2 gamma and LAB (see
Bruce's
> curves) then what is gained by output at LAB?

Well, it's a choice that was made. You'd have to ask Roy. But it seems
a likely choice given that all out icc based color output it
referenced to it too. You have to pick something right? It seems no
one picks the same target to hit.

...
then a bunch of math stuff...
Steve, not going there. NOT GONNA DO IT!
The excedrin bottle is nearly empty, the dog needs to go out, my
clients are screaming, my butt hurts...

How about this? If the output dynamic range is by nature smaller than
the "abstract" space of say, LAB, then there is indeed compression, right?
And what you are saying is that even if one "linearizes to LAB" that
output to the smaller range that the resulting slope is no longer the
same as LAB, right?
These working spaces are simply that, descriptors. There is no real
world equivalent of absolute black or white that is relevant to us
with this work. When translated to any useful viewing of the art,
whether monitor, paper, whatever, there is by nature always a
compression if the image content utilizes the full range of the
working space.
The resulting tonal progression is something porportionally or somehow
mathematically related to the reference, but not exactly the same rate
of change. If we insist on maintaining that slope in some part of the
scale, then yes, there would be something clipped, or compressed at
the extremes, or whatever.
But what would be the point? What is so sancrosanct about maintaining
that slope somewhere? The whole point is to maintain the tonal
relationships, unless of course you want come up with your own unique
definition of "linearization".

Also, this all flies in the face of maintaining some standard middle
gray density value. If I linearize uncoated Somerset Velvet (low dmax)
and PhotoRag (high dmax) middle gray value in the file will print
differently on one paper than the other. Rightly so! I want those
relationships I worked so hard on maintained. If I want to match some
gray on both prints, obviously I'll have to massively compress my
shadow values in the uncoated version. The concept of middle gray has
been redefined. Now it really IS in the middle. Actually it always was
for us zone freaks, gray card be damned.
If that's what one is attempting (a specific middle gray target
density), every paper and ink combination would have to be linearized
to a different gamma, based on paper white and dmax, and the tonal
relationships in a file when printed on them all would be different.

Is this getting to what you are talking about? If so, I can only say
that to my knowledge, linearization by today's standard means a
uniform compression as above, so then a deviation from the strict
slope of the reference space. I think that's what you have been trying
to get me to absorb.
But I'm not sure there is another really useful way to go about this.
If you come up with one, be careful who you share it with before you
make your own trip to the patent office <G>.
If you are attempting to point out that the process of linearization
to a given standard like LAB is not strictly the same as the reference
and therefore not really "linearization" then yes, you are right.
I think I get your point now, if not, please forgive me, I have to
take the dog out.
Tyler

By the way, by strict definition, colormetric icc color
transformations maintain the relationships as you suggest from paper
white on down with Black Point Compensation off, then of course the
shadows clip if out of gamut. Someone correct me if that's wrong.

Hi Tyler and others following along

No maths, just managing image tones to print tones - what a B&W RIP is all
about. 

With regard to LAB - you sold me.  Even as a (final) edit tool.  In a colour
world LAB is not intuitive - what's with the a b mumbo jumbo?  Too hard!
But in a B&W world it couldn't be easier... a and b are 0!  Cool.  A simple
scale from 0 (white) to 100 (black) with 50 in the middle - what a pity it
isn't 0 black to 1 white but never mind.  And, LAB=50 equals my Kodak grey
card! Cool.  And to boot it supposedly matches the way the eye "sees".
Cool.  I'm sold.  Let's pick it and stick to it. Where can I get a step
wedge in LAB?  

At a minimum with LAB I can place a grey card in the scene, expose to it,
check to make sure it has a value of LAB=50 in the image file with my
eyedropper (a test of my exposure) and with a well profiled monitor and
colorsync doing the translation to my monitor's (hardware) space - huge sigh
of relief here, thank god I don't have to do this myself - look at Kodak
grey on screen! Now for the print....ooops, no colorsync to help me here. Oh
no!

Here is where we are having difficulty.  Maybe a simple example would help.

A teacher of digital photography wishes to test his/her students' ability to
expose and print a scene correctly.  This is not a test of their subjective
artistic interpretation of the scene but of their technical method and
ability. (He/she will can't test their artistic ability just help them
explore it.) So the teacher goes to the local hardware store and buys three
paints.  The first is almost bright white.  The second is chosen very
carefully so that when it is dry it is Kodak middle grey with 18%
reflectance.  The hardware store is all out of very dark black but they have
a very very dark grey - kind of sort of almost black.  The teacher paints a
wall with the "white" paint and, once it is dry, paints two large squares on
the white wall, one Kodak grey and the other with the near black.  The
teacher wants the students to photograph the image and then print it on two
printers.  The printers are both Epson 1280s but one has Eboni ink and EEM
paper while the other has Epson PK ink and Epson Premium Semi-gloss paper.

Just before the students start their exercise the teacher takes out his
Eye-One and measures the three colours.  He gets LAB readings of 96.5 for
the white, 50 for the mid grey as expected, and 16 for the dark grey.  He
doesn't let the students know the answers but he does tell them that the mid
grey is the same as their Kodak grey card.  On the assumption that all the
students do perfect exposures how will these print using QTR on the two
printers?

The digital image file could not be simpler.  A bunch of pixels at 96.5, a
bunch at 50 and a bunch at 16, in LAB terms.

Take printer No 1.  In setting up this printer we would have printed a step
wedge, measured the printed densities and written LINEARIZE= [density
readings] in the curve .txt file.  It is EEM with Eboni and so dMin is 0.04
(LAB=96.5) and dMax is 1.68 (LAB=16), conveniently!   The printer will not
print the scene as recorded.  It will put some ink down for the "white" wall
and not enough ink down for the "dark grey" square.  I do not know how it
will print the Kodak grey.  The rendition will be better on the second
printer but is still incorrect.

But, you might say, my image file does not use the full tonal range.  I
should use levels to shift my black point to the right and my white point to
the left.  Ok so I do this and the image file is altered.  Now, and only
because the dMin of the printer equals the lower end of my adjusted image
tonal range and the printer dMax equals the high end of my adjusted image
tonal range, the first printer will print the "white" correctly and "dark
grey" correctly.  I, again, have no idea how the Kodak grey will be printed.
Now what happens if I then take this adjusted image file and print to the
second printer.  It will print the dark grey too dark, the white too white
(just), and again I have no idea how it will print the Kodak grey.  I also
can only fiddle with a soft proof to get it to look kind of sort of right.

I would simply argue that this is not a satisfactory workflow.  If I can't
rely on my workflow to print the simplest of (in-gamut) images correctly
then I am simply fiddling in the dark.  It's no wonder everyone breathed a
massive sigh of relief when Carl figured out a way to soft proof with the
Eye-One! At least then a partial light came on in the room and we could
fiddle with the before and after on screen.

Now, yes, to get the workflow to a more satisfactory position does require a
little math.  If you followed the methodology I have been proposing the
image would print perfectly on BOTH printers without adjustment to the image
file WHICH WAS CORRECTLY EXPOSED.

This doesn't fly in the face of "maintaining some sort of middle grey" - it
achieves it.  

(BTW Paul is the only guy I see out there consistently targeting a
particular density for mid grey 50%.  He has been at times a little unsure
about what that mid should be but at least it is targeted.  Paul, if you
believe in LAB make it LAB=50 which will match your grey card's 18%
reflectance.  In Grey Gamma 2.2/Adobe RGB this is about a step of 54.2.  The
50% step in a LAB step wedge should, surprisingly, print at LAB=50 or a
density of 0.73.)

As for real black, I agree that there isn't any real world real black
(although Einstein would probably say it is out there somewhere).  But there
are very real world examples of near black.  Thankfully colorsync manages
this issue for our display and aligns real black to monitor black with
whatever "intent" we have selected (interesting that they called it
"intent").  In general it doesn't matter so much these days because the
display a  far broader range of tones than we can ever hope to print.  But
we don't have colorsync by our side when printing with QTR (or any other non
colorsynced RIP).  The management and repositioning of out-of-gamut colours
has to be managed manually.  Unfortunately this involves a little bit of
maths.

I hope you will persevere with me on this and I hope people like Roy are
listening in.

Like that LAB!

Steve

PS: A couple of additional comments below:


> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 07 Dec 2004 02:03:58 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
> <stevekale@b...> wrote:
> ...
>> I understood you.  I guess I was raising the counter question that
> if there
>> is little difference in grey scale between 2.2 gamma and LAB (see
> Bruce's
>> curves) then what is gained by output at LAB?
> 
> Well, it's a choice that was made. You'd have to ask Roy. But it seems
> a likely choice given that all out icc based color output it
> referenced to it too. You have to pick something right? It seems no
> one picks the same target to hit.
> 
> ...
> then a bunch of math stuff...
> Steve, not going there. NOT GONNA DO IT!
> The excedrin bottle is nearly empty, the dog needs to go out, my
> clients are screaming, my butt hurts...
> 
> How about this? If the output dynamic range is by nature smaller than
> the "abstract" space of say, LAB, then there is indeed compression, right?
> And what you are saying is that even if one "linearizes to LAB" that
> output to the smaller range that the resulting slope is no longer the
> same as LAB, right?
> These working spaces are simply that, descriptors. There is no real
> world equivalent of absolute black or white that is relevant to us
> with this work. When translated to any useful viewing of the art,
> whether monitor, paper, whatever, there is by nature always a
> compression if the image content utilizes the full range of the
> working space.
> The resulting tonal progression is something porportionally or somehow
> mathematically related to the reference, but not exactly the same rate
> of change. 
 
The existing relationship to reference is variable and changes for every
ink/paper combination.

> If we insist on maintaining that slope in some part of the
> scale, then yes, there would be something clipped, or compressed at
> the extremes, or whatever.

Only if we sent it out of gamut tones.  We can avoid this in a CONTROLLED
fashion with curves.


> But what would be the point? What is so sancrosanct about maintaining
> that slope somewhere? The whole point is to maintain the tonal
> relationships, unless of course you want come up with your own unique
> definition of "linearization".

I am not defining linearization just using it.  Linearization comes from the
fact that the first derivative (ie LOG) of the exposure/density curve of a
gamma space is linear.  (BTW note that the first derivative of LAB would not
appear to be linear else Bruce would have been able to derive the gamma with
perfect fit.)  Whoops!  Sorry I said no maths.

> 
> Also, this all flies in the face of maintaining some standard middle
> gray density value. If I linearize uncoated Somerset Velvet (low dmax)
> and PhotoRag (high dmax) middle gray value in the file will print
> differently on one paper than the other. Rightly so! I want those
> relationships I worked so hard on maintained. If I want to match some
> gray on both prints, obviously I'll have to massively compress my
> shadow values in the uncoated version. The concept of middle gray has
> been redefined. Now it really IS in the middle. Actually it always was
> for us zone freaks, gray card be damned.
> If that's what one is attempting (a specific middle gray target
> density), every paper and ink combination would have to be linearized
> to a different gamma, based on paper white and dmax, and the tonal
> relationships in a file when printed on them all would be different.
> 
> Is this getting to what you are talking about? If so, I can only say
> that to my knowledge, linearization by today's standard means a
> uniform compression as above, so then a deviation from the strict
> slope of the reference space. I think that's what you have been trying
> to get me to absorb.
> But I'm not sure there is another really useful way to go about this.
> If you come up with one, be careful who you share it with before you
> make your own trip to the patent office <G>.
> If you are attempting to point out that the process of linearization
> to a given standard like LAB is not strictly the same as the reference
> and therefore not really "linearization" then yes, you are right.

I am saying that linearization to LAB should actually do that, not some
other function whose relationship to LAB changes for each and every
ink/paper combination.

> I think I get your point now, if not, please forgive me, I have to
> take the dog out.
> Tyler
> 
> By the way, by strict definition, colormetric icc color
> transformations maintain the relationships as you suggest from paper
> white on down with Black Point Compensation off, then of course the
> shadows clip if out of gamut. Someone correct me if that's wrong.
>

Steve,

By the way, I'm starting to use Lab b axis to judge my simple profiles --
it's easier.

I'm also half considering a full-on Lab low gamut inkset controlled by one
of the affordable B&W rips.

Paul
www.PaulRoark.com 
_____________________

-----Original Message-----
From: Steve Kale [mailto:stevekale@...] 
Sent: Tuesday, December 07, 2004 4:25 AM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Tonal range and linearization


Hi Tyler and others following along

No maths, just managing image tones to print tones - what a B&W RIP is all
about. 

With regard to LAB - you sold me.  Even as a (final) edit tool.  In a colour
world LAB is not intuitive - what's with the a b mumbo jumbo?  Too hard!
But in a B&W world it couldn't be easier... a and b are 0!  Cool.  A simple
scale from 0 (white) to 100 (black) with 50 in the middle - what a pity it
isn't 0 black to 1 white but never mind.  And, LAB=50 equals my Kodak grey
card! Cool.  And to boot it supposedly matches the way the eye "sees".
Cool.  I'm sold.  Let's pick it and stick to it. Where can I get a step
wedge in LAB?  

At a minimum with LAB I can place a grey card in the scene, expose to it,
check to make sure it has a value of LAB=50 in the image file with my
eyedropper (a test of my exposure) and with a well profiled monitor and
colorsync doing the translation to my monitor's (hardware) space - huge sigh
of relief here, thank god I don't have to do this myself - look at Kodak
grey on screen! Now for the print....ooops, no colorsync to help me here. Oh
no!

Here is where we are having difficulty.  Maybe a simple example would help.

A teacher of digital photography wishes to test his/her students' ability to
expose and print a scene correctly.  This is not a test of their subjective
artistic interpretation of the scene but of their technical method and
ability. (He/she will can't test their artistic ability just help them
explore it.) So the teacher goes to the local hardware store and buys three
paints.  The first is almost bright white.  The second is chosen very
carefully so that when it is dry it is Kodak middle grey with 18%
reflectance.  The hardware store is all out of very dark black but they have
a very very dark grey - kind of sort of almost black.  The teacher paints a
wall with the "white" paint and, once it is dry, paints two large squares on
the white wall, one Kodak grey and the other with the near black.  The
teacher wants the students to photograph the image and then print it on two
printers.  The printers are both Epson 1280s but one has Eboni ink and EEM
paper while the other has Epson PK ink and Epson Premium Semi-gloss paper.

Just before the students start their exercise the teacher takes out his
Eye-One and measures the three colours.  He gets LAB readings of 96.5 for
the white, 50 for the mid grey as expected, and 16 for the dark grey.  He
doesn't let the students know the answers but he does tell them that the mid
grey is the same as their Kodak grey card.  On the assumption that all the
students do perfect exposures how will these print using QTR on the two
printers?

The digital image file could not be simpler.  A bunch of pixels at 96.5, a
bunch at 50 and a bunch at 16, in LAB terms.

Take printer No 1.  In setting up this printer we would have printed a step
wedge, measured the printed densities and written LINEARIZE= [density
readings] in the curve .txt file.  It is EEM with Eboni and so dMin is 0.04
(LAB=96.5) and dMax is 1.68 (LAB=16), conveniently!   The printer will not
print the scene as recorded.  It will put some ink down for the "white" wall
and not enough ink down for the "dark grey" square.  I do not know how it
will print the Kodak grey.  The rendition will be better on the second
printer but is still incorrect.

But, you might say, my image file does not use the full tonal range.  I
should use levels to shift my black point to the right and my white point to
the left.  Ok so I do this and the image file is altered.  Now, and only
because the dMin of the printer equals the lower end of my adjusted image
tonal range and the printer dMax equals the high end of my adjusted image
tonal range, the first printer will print the "white" correctly and "dark
grey" correctly.  I, again, have no idea how the Kodak grey will be printed.
Now what happens if I then take this adjusted image file and print to the
second printer.  It will print the dark grey too dark, the white too white
(just), and again I have no idea how it will print the Kodak grey.  I also
can only fiddle with a soft proof to get it to look kind of sort of right.

I would simply argue that this is not a satisfactory workflow.  If I can't
rely on my workflow to print the simplest of (in-gamut) images correctly
then I am simply fiddling in the dark.  It's no wonder everyone breathed a
massive sigh of relief when Carl figured out a way to soft proof with the
Eye-One! At least then a partial light came on in the room and we could
fiddle with the before and after on screen.

Now, yes, to get the workflow to a more satisfactory position does require a
little math.  If you followed the methodology I have been proposing the
image would print perfectly on BOTH printers without adjustment to the image
file WHICH WAS CORRECTLY EXPOSED.

This doesn't fly in the face of "maintaining some sort of middle grey" - it
achieves it.  

(BTW Paul is the only guy I see out there consistently targeting a
particular density for mid grey 50%.  He has been at times a little unsure
about what that mid should be but at least it is targeted.  Paul, if you
believe in LAB make it LAB=50 which will match your grey card's 18%
reflectance.  In Grey Gamma 2.2/Adobe RGB this is about a step of 54.2.  The
50% step in a LAB step wedge should, surprisingly, print at LAB=50 or a
density of 0.73.)

As for real black, I agree that there isn't any real world real black
(although Einstein would probably say it is out there somewhere).  But there
are very real world examples of near black.  Thankfully colorsync manages
this issue for our display and aligns real black to monitor black with
whatever "intent" we have selected (interesting that they called it
"intent").  In general it doesn't matter so much these days because the
display a  far broader range of tones than we can ever hope to print.  But
we don't have colorsync by our side when printing with QTR (or any other non
colorsynced RIP).  The management and repositioning of out-of-gamut colours
has to be managed manually.  Unfortunately this involves a little bit of
maths.

I hope you will persevere with me on this and I hope people like Roy are
listening in.

Like that LAB!

Steve

PS: A couple of additional comments below:


> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 07 Dec 2004 02:03:58 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
> <stevekale@b...> wrote:
> ...
>> I understood you.  I guess I was raising the counter question that
> if there
>> is little difference in grey scale between 2.2 gamma and LAB (see
> Bruce's
>> curves) then what is gained by output at LAB?
> 
> Well, it's a choice that was made. You'd have to ask Roy. But it seems
> a likely choice given that all out icc based color output it
> referenced to it too. You have to pick something right? It seems no
> one picks the same target to hit.
> 
> ...
> then a bunch of math stuff...
> Steve, not going there. NOT GONNA DO IT!
> The excedrin bottle is nearly empty, the dog needs to go out, my
> clients are screaming, my butt hurts...
> 
> How about this? If the output dynamic range is by nature smaller than
> the "abstract" space of say, LAB, then there is indeed compression, right?
> And what you are saying is that even if one "linearizes to LAB" that
> output to the smaller range that the resulting slope is no longer the
> same as LAB, right?
> These working spaces are simply that, descriptors. There is no real
> world equivalent of absolute black or white that is relevant to us
> with this work. When translated to any useful viewing of the art,
> whether monitor, paper, whatever, there is by nature always a
> compression if the image content utilizes the full range of the
> working space.
> The resulting tonal progression is something porportionally or somehow
> mathematically related to the reference, but not exactly the same rate
> of change. 
 
The existing relationship to reference is variable and changes for every
ink/paper combination.

> If we insist on maintaining that slope in some part of the
> scale, then yes, there would be something clipped, or compressed at
> the extremes, or whatever.

Only if we sent it out of gamut tones.  We can avoid this in a CONTROLLED
fashion with curves.


> But what would be the point? What is so sancrosanct about maintaining
> that slope somewhere? The whole point is to maintain the tonal
> relationships, unless of course you want come up with your own unique
> definition of "linearization".

I am not defining linearization just using it.  Linearization comes from the
fact that the first derivative (ie LOG) of the exposure/density curve of a
gamma space is linear.  (BTW note that the first derivative of LAB would not
appear to be linear else Bruce would have been able to derive the gamma with
perfect fit.)  Whoops!  Sorry I said no maths.

> 
> Also, this all flies in the face of maintaining some standard middle
> gray density value. If I linearize uncoated Somerset Velvet (low dmax)
> and PhotoRag (high dmax) middle gray value in the file will print
> differently on one paper than the other. Rightly so! I want those
> relationships I worked so hard on maintained. If I want to match some
> gray on both prints, obviously I'll have to massively compress my
> shadow values in the uncoated version. The concept of middle gray has
> been redefined. Now it really IS in the middle. Actually it always was
> for us zone freaks, gray card be damned.
> If that's what one is attempting (a specific middle gray target
> density), every paper and ink combination would have to be linearized
> to a different gamma, based on paper white and dmax, and the tonal
> relationships in a file when printed on them all would be different.
> 
> Is this getting to what you are talking about? If so, I can only say
> that to my knowledge, linearization by today's standard means a
> uniform compression as above, so then a deviation from the strict
> slope of the reference space. I think that's what you have been trying
> to get me to absorb.
> But I'm not sure there is another really useful way to go about this.
> If you come up with one, be careful who you share it with before you
> make your own trip to the patent office <G>.
> If you are attempting to point out that the process of linearization
> to a given standard like LAB is not strictly the same as the reference
> and therefore not really "linearization" then yes, you are right.

I am saying that linearization to LAB should actually do that, not some
other function whose relationship to LAB changes for each and every
ink/paper combination.

> I think I get your point now, if not, please forgive me, I have to
> take the dog out.
> Tyler
> 
> By the way, by strict definition, colormetric icc color
> transformations maintain the relationships as you suggest from paper
> white on down with Black Point Compensation off, then of course the
> shadows clip if out of gamut. Someone correct me if that's wrong.
> 





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Steve,

I think you and Tyler are at an impass.  You believe that the absolute 
value (of brightness) matters.  Tyler believes that everything is relative.

In terms of "the literature", Tyler is right.  The commonly held belief is 
that the absolute value of brightness doesn't matter.  That the human 
vision system will adapt to the scenes or images dynamic range.  See 
"Digital Image Processing", by William K. Pratt or similar works for a 
complete discussion of why this is.

I'm more of a relativist, too.  The curves I create are visually linear 
from paper-white to ink-black with middle grey falling where it may.  But 
this discussion has made me reconsider this approach and question my 
assumptions.  Or, at least made me consider an alternative: I'm going to 
create some curves that put printed middle-grey at Kodak middle grey, but 
that also make my displayed contrast equal my printed contrast.  Let the 
S-curve fall where it may!

Really, there is no right or wrong here.  It's just how you choose to work.

-Keith


At 04:24 AM 12/7/2004, you wrote:

>Hi Tyler and others following along
>
>No maths, just managing image tones to print tones - what a B&W RIP is all
>about.
>
>With regard to LAB - you sold me.  Even as a (final) edit tool.  In a colour

<snip>

> 
> I hope you will persevere with me on this and I hope people like Roy are
> listening in.
> 
> Like that LAB!
> 
> Steve
> 

Hi Steve,

I've actually been following the thread all along and it sure has sparked a
lot of interesting questions.

I like comparing things and linearizing in Lab because it's supposed to the ideal
match for human vision.  I.e. linear Lab ought to be linear visually -- in other
words a difference from Lab 15 to 20 (5%) is comparable to a difference from
Lab 50 to 55 (also 5%) and Lab 85 to 90.  This makes sense as the best use of
the 256 values you get for an 8bit data file.

Unfortunately Photoshop doesn't have a Lab oriented grayspace.  We could use
Lab spaces but first they have 3 channels so your files will be triple the size with
no more info.  Second I think when you print, PS will get you "out of Lab" in the
conversion to grayscale doing a profile mapping for you (or is it to you :) ).

The main reason I've always used gray gamma 2.2 along with adobe RGB is that
with the eye dropper you can see the 8 bit values in the file.  K gives only 0-100
but underneath its really 0-255. You can see 0-255 in the RGB values but they
are only correct if the gray and color spaces have the same gamma. (Profile
conversions are always going on).


Roy

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> Hi Tyler and others following along...

Well, at least I understand what you are getting at now, even though I
quite adamantly disagree. But lack of consensus is better than lack of
understanding.

Your classroom example has some problems... You assume if all three
tones are properly exposed their relationships will be correct.
Really? You've found a perfect straight line film/processing combo?
The scanner you used was dead linear, or perfectly profiled profiled?
Or perhaps you captured the scene. What were the characteristics of
that device? How was the file processed? Anyway, different conversation...


> > The resulting tonal progression is something porportionally or somehow
> > mathematically related to the reference, but not exactly the same rate
> > of change. 
>  
> The existing relationship to reference is variable and changes for every
> ink/paper combination.

Yes! Thanks goodness! They all have different characteristics. 
...

> >...The whole point is to maintain the tonal
> > relationships, unless of course you want come up with your own unique
> > definition of "linearization".
> 
> I am not defining linearization just using it...
...and...
> I am saying that linearization to LAB should actually do that, not some
> other function whose relationship to LAB changes for each and every
> ink/paper combination.

OK, strictly yes. But the standard use of the term linearization for
an output device these days is not that, and that's what I'm talking
about. Even though the "linearization" results in a compression, the
tonal relationships within that range bear a relationship to LAB from
dmin to dmax, you must admit. Had one done a similar "linearization"
to gamma 2.2 (or whatever) that same relationship would hold between
the linearized output and 2.2, even though compressed. Strictly, the
rate of change, is no longer exactly that of the target, granted.
We are after two completely different things. You want middle gray to
be middle gray whether you are printing on a brown paper bag or
Photorag, utilizing some (in this extreme example) rather massive
change in the other tonal relationships, and those changes will likely
be different between middle gray and dmin, and middle gray and dmax.
I need all those relationships to be proportionally maintained,
absolutely, and that is what I think is generally accepted as
linearization, even though that moniker may be incorrect by strict
definition.

So there we are, good luck in your efforts...
Tyler

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Keith Douglas
<kdouglas@q...> wrote:
> Steve,
> 
> I think you and Tyler are at an impass.  You believe that the absolute 
> value (of brightness) matters.  Tyler believes that everything is
relative.
> 
> In terms of "the literature", Tyler is right.

Keith, thanks, but I don't think it's a matter of "right". In fact if
one wants to make sure proper use of science and language is
maintained, Steve may be "right" and common practice "wrong".
What it gets down to in the end for me, is what is most useful for the
work at hand. This method of calibration is the most developed by the
community and the most perfected by developers, for me it's invaluable.
I just won't call it "linearization" any more around Steve <G>. Who
knows, perhap's he'll come up with something equally useful, and then
I'll be all over it too.
Tyler

I simply want a RIP that is calibrated to print what I ask.  One that
doesn't change my image if it is all in-gamut and no tonal compression is
necessary. I, like Ansel did, want to know that if I expose a part of the
scene to a particular density that it will end up there in the print - the
rest of the parts of the print will fall as they are exposed...unless I
choose to modify their exposure with a PS curve (he clipped - or dodged and
burned). When I do this curve I want to know that it is this curve which
alters the image and nothing else.  Nice and simple.  One can debate to what
benchmark (gamma 1.8, 2.2, LAB or whatever) the system should be calibrated
but let it at least be calibrated to what we decide and have that
calibration be consistent in its application.

I started where you are now.  Targeting middle grey is what Paul does
manually (he just chose a different grey from the one you are about to try).
You will find that for each ink .txt file you will need a different curve to
reset your mid grey to whatever density you choose as your reference.  (This
is because QTR is not calibrated to a defined space.)  And your curve will
affect the results of the other parts of the image in different ways.  You
will need a curve just to get a QTR ink curve to print your selected Kodak
grey at 50% - just to get a known value for 1 step.  The curve to achieve
this for EEM is different for EPSG - in fact for any ink/paper combination.
The tonal compression that occurs is then a result of two curves - the one
you did and the one implicit in the RIP calibration (the latter not
visible).  

If the system were calibrated as I am proposing you will find that ANY PS
curve you use to manage the necessary image file compression to the printer
space will not affect your mid grey as long as your curve passes through
128/128 - ie unless you change it on purpose - nice and visual.  If all
image values are in gamut it prints perfectly.  If I know my paper's dynamic
range (dMin and dMax) I can look at the histogram and see straight away what
is in gamut and what is not.  I can then do whatever curve I want to
directly manage out-of-gamut tones (remember we have to manually manage
these because we don't have colorsync and one of its 4 options doing it for
us) and then, with an in-gamut image on screen where I can see it, get it to
print perfectly - no guessing.  This curve - up in front of me in PS...I can
see by its shape the exact nature by which inputs are mapped to printed
outputs - defines the image's complete change from file (exposure) to print
(rendition).

You are right that it is how you choose to work but why make yourself have
to guess the system?  The whole point of calibration is to know in advance
the result you will get.

A word on soft proofing.  When you do a soft proof in a color managed world
you are looking at the combined effect of two things: (a) a determination of
what is out of gamut, (b) the effect of the method selected for dealing with
out of gamut colour (absolute, relative, perceptual etc) and (c) a complete
management of the different shape (gamma etc) of the two spaces.  (a) is
determined when the printer profile is compared with the image file.  In B&W
this is easy - it is just the pixels with values outside dMin to dMax and
these two points are calculated very easily.  As I said before you can see
these just by looking at the histogram.  Because (b) is such a complicated
exercise in the colour world those ingenious folks who developed colorsync
gave us four methods to choose from and then once selected the remapping is
done automatically.  Again, in a B&W world dealing with out-of-gamut values
is infinitely easier.  We know where they are as I said. And they can be
dealt with with a simple curve. With regard to (c), if we are not concerned
with hue, it is very easy to calibrate the printer to match the workspace
(whatever that may be!) and so (c) is very unnecessary in a B&W hueless
world. I would liken our current situation to making things way more
difficult than they need to be and then finding soft proofing to pull us out
of a situation that we needn't have been in in the first place!

Well even if I am not winning at least I have got you thinking.  Come back
when you have had some fun with those curves  ;-)


Steve

> From: Keith Douglas <kdouglas@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 07 Dec 2004 09:19:41 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> Steve,
> 
> I think you and Tyler are at an impass.  You believe that the absolute
> value (of brightness) matters.  Tyler believes that everything is relative.
> 
> In terms of "the literature", Tyler is right.  The commonly held belief is
> that the absolute value of brightness doesn't matter.  That the human
> vision system will adapt to the scenes or images dynamic range.  See
> "Digital Image Processing", by William K. Pratt or similar works for a
> complete discussion of why this is.
> 
> I'm more of a relativist, too.  The curves I create are visually linear
> from paper-white to ink-black with middle grey falling where it may.  But
> this discussion has made me reconsider this approach and question my
> assumptions.  Or, at least made me consider an alternative: I'm going to
> create some curves that put printed middle-grey at Kodak middle grey, but
> that also make my displayed contrast equal my printed contrast.  Let the
> S-curve fall where it may!
> 
> Really, there is no right or wrong here.  It's just how you choose to work.
> 
> -Keith
> 
>

> From: Roy Harrington <roy@...>

 
> Hi Steve,
> 
> I've actually been following the thread all along and it sure has sparked a
> lot of interesting questions.
> 
> I like comparing things and linearizing in Lab because it's supposed to the
> ideal
> match for human vision.  I.e. linear Lab ought to be linear visually -- in
> other
> words a difference from Lab 15 to 20 (5%) is comparable to a difference from
> Lab 50 to 55 (also 5%) and Lab 85 to 90.  This makes sense as the best use of
> the 256 values you get for an 8bit data file.

Yep Tyler sold me on this.  But I don't believe QTR "linearizes in LAB".
This is a crucial point and one that I would like to explore further with
you - offline if necessary (everyone else breaths a sigh of relief!).  LAB
has a defined density curve - as pixel values (ie exposure) increase(s) from
0 (black) to 1 (white) LAB defines a particular shade of grey (if a=b=0), ie
density output.  If this curve is "the way the eye sees" then we need to
have our printed output from 0 to 1 match this curve.  We know we can't get
perfect 0 and perfect 1 but we can get a portion of the range in between.  I
believe that to be linearized to LAB this portion should take on the same
characteristics as the LAB curve.

Setting 0 to dMax and 1 to dMin and straight lining the LAB values in
between is analogous to creating an entirely new colour space. Plot the
density curve and compare it with LAB (and even gamma 2.2).
> 
> Unfortunately Photoshop doesn't have a Lab oriented grayspace.  We could use
> Lab spaces but first they have 3 channels so your files will be triple the
> size with
> no more info.  

Yes agreed.

> Second I think when you print, PS will get you "out of Lab" in
> the
> conversion to grayscale doing a profile mapping for you (or is it to you :) ).
> 
Sorry I am not sure what you mean by this.

> The main reason I've always used gray gamma 2.2 along with adobe RGB is that
> with the eye dropper you can see the 8 bit values in the file.  K gives only
> 0-100
> but underneath its really 0-255. You can see 0-255 in the RGB values but they
> are only correct if the gray and color spaces have the same gamma. (Profile
> conversions are always going on).

Yes that is correct.  But as we know from Bruce Lindbloom's site the gamma
best able to approximate LAB greyscale is a gamma of around the "standard"
2.2.  As I said earlier, I might tolerate working in 2.2 and then printing
in LAB only if the printer were actually calibrated to LAB ('cos only then
would 2.2 be roughly close to LAB).


Cheers

Steve

> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 07 Dec 2004 18:06:52 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] Re: Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
> <stevekale@b...> wrote:
>> Hi Tyler and others following along...
> 
> Well, at least I understand what you are getting at now, even though I
> quite adamantly disagree. But lack of consensus is better than lack of
> understanding.
> 
> Your classroom example has some problems... You assume if all three
> tones are properly exposed their relationships will be correct.
> Really? You've found a perfect straight line film/processing combo?
> The scanner you used was dead linear, or perfectly profiled profiled?
> Or perhaps you captured the scene. What were the characteristics of
> that device? How was the file processed? Anyway, different conversation...
> 

For these parts of the workflow I have colorsync to help me.  For the print
end I unfortunately don't.

> 
>>> The resulting tonal progression is something porportionally or somehow
>>> mathematically related to the reference, but not exactly the same rate
>>> of change. 
>>  
>> The existing relationship to reference is variable and changes for every
>> ink/paper combination.
> 
> Yes! Thanks goodness! They all have different characteristics.
> ...
> 
>>> ...The whole point is to maintain the tonal
>>> relationships, unless of course you want come up with your own unique
>>> definition of "linearization".
>> 
>> I am not defining linearization just using it...
> ...and...
>> I am saying that linearization to LAB should actually do that, not some
>> other function whose relationship to LAB changes for each and every
>> ink/paper combination.
> 
> OK, strictly yes. But the standard use of the term linearization for
> an output device these days is not that, and that's what I'm talking
> about. Even though the "linearization" results in a compression, the
> tonal relationships within that range bear a relationship to LAB from
> dmin to dmax, you must admit. Had one done a similar "linearization"
> to gamma 2.2 (or whatever) that same relationship would hold between
> the linearized output and 2.2, even though compressed. Strictly, the
> rate of change, is no longer exactly that of the target, granted.
> We are after two completely different things.

As I said in the note Roy, the way linearization is done at the moment
(straight-lining the LAB values) is analogous to creating a whole new colour
space. You have lost any consistent relationship to LAB.  A straight line
over 0 to 1 of L=16 to L=96 is completely different to 0 to 1 with L=5 to
L=96.  What's more the density curve generated by this is nothing like that
defined by LAB, the way the eye sees and all that good stuff.

>You want middle gray to
> be middle gray whether you are printing on a brown paper bag or
> Photorag, utilizing some (in this extreme example) rather massive
> change in the other tonal relationships, and those changes will likely
> be different between middle gray and dmin, and middle gray and dmax.
> I need all those relationships to be proportionally maintained,
> absolutely, and that is what I think is generally accepted as
> linearization, even though that moniker may be incorrect by strict
> definition.
> 

Well a brown paper bag is an extreme example and I wouldn't generally
recommend using it as a paper base for B&W printing. dMin is a pretty high
density and the available tonal range is actually quite small (likely much
smaller than EEM).  But yes it is capable of some tonal range - remember I
don't actually care that it is brown just that it has a low maximum
reflectance.  Whether mid grey is in-gamut or not would depend on how dark
the brown of the bag is.  If it is out of gamut I don't get it in the print
- period - and I would have to remap middle grey in my image to an in-gamut
value.  I probably wouldn't like the necessary compression and choose
another paper.

Cheers

Steve

LOL - unfortunately I am not smart enough to write a programme like QTR and
so I am stuck with what's available - I am just a dumb banker.  But then I
still don't mind challenging "common practice" if it doesn't make sense to
me and I think there is a better way.

By the way, to all and sundry, I want to say that I think QTR is an awesome
programme.  I use it. I write my own curves for it.  And I do the
"linearization whatsimecallit".  I am not questioning the power of the
programme, just how it is calibrated.  I am even prepared to agree that it
is calibrated according to common practice.  I am just questioning common
practice.

Pay your $50 and have fun with it!

Steve

> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 07 Dec 2004 18:16:23 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Keith Douglas
> <kdouglas@q...> wrote:
>> Steve,
>> 
>> I think you and Tyler are at an impass.  You believe that the absolute
>> value (of brightness) matters.  Tyler believes that everything is
> relative.
>> 
>> In terms of "the literature", Tyler is right.
> 
> Keith, thanks, but I don't think it's a matter of "right". In fact if
> one wants to make sure proper use of science and language is
> maintained, Steve may be "right" and common practice "wrong".
> What it gets down to in the end for me, is what is most useful for the
> work at hand. This method of calibration is the most developed by the
> community and the most perfected by developers, for me it's invaluable.
> I just won't call it "linearization" any more around Steve <G>. Who
> knows, perhap's he'll come up with something equally useful, and then
> I'll be all over it too.
> Tyler
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
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--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
...
snip...
> A word on soft proofing.  When you do a soft proof in a color
managed world
> you are looking at the combined effect of two things: (a) a
determination of
> what is out of gamut, (b) the effect of the method selected for
dealing with
> out of gamut colour (absolute, relative, perceptual etc) and (c) a
complete
> management of the different shape (gamma etc) of the two spaces....

Actually, the way most of us are using softproof for monochromatic out
put, most of this is irrelevant.
By checking the "preserve color numbers" box, we are taking advantage
of the device to lab LUTs only. No icc conversion is going to take
place when printing, and we are not asking preview to simulate that
conversion for us. Therefore intents are irrelevant, and grayed out.
We are looking at a monitor representation of how the output system
prints, period, including paper white and ink black if we choose to
use them.
Tyler

I'm on windows, so I don't have the luxury of using Roy's curve creation 
tools.  I've started from scratch with Excel and Matlab.  Here's an 
overview of what I've done so far (using UT1 on a 1280 btw):

Print K, C and LC step-wedges with (mathematically) linear transfer 
function for QTR.
Measure dmax and gamma for each, create 1/gamma curves.  This roughly 
linearizes the output.
Print K,C and LC step-wedges with my new 1/gamma curves.
Measure each step on the step-wedge.  Fine-tune curve to give linear 
brightness from dmin to dmax for each ink.
Partition these three inks to give overall linear brightness.

Here's where I've stopped before.  The output is very linear (except I'm 
still having trouble with the transitions between inks).  Middle grey is 
the exact middle between paper-white and ink-black.

Now what I'm thinking is adding an overall curve to first map (128,128,128) 
to Kodak middle-grey.  Then I'll adjust the slope of the curve to make the 
on-screen contrast the same as the 
printed-contrast.  What-I-see-is-what-I-get.

-Keith



At 10:19 AM 12/7/2004, you wrote:

>I started where you are now.  Targeting middle grey is what Paul does
>manually (he just chose a different grey from the one you are about to try).
>You will find that for each ink .txt file you will need a different curve to
>reset your mid grey to whatever density you choose as your reference.  (This
>is because QTR is not calibrated to a defined space.)  And your curve will
>affect the results of the other parts of the image in different ways.  You
>will need a curve just to get a QTR ink curve to print your selected Kodak
>grey at 50% - just to get a known value for 1 step.  The curve to achieve
>this for EEM is different for EPSG - in fact for any ink/paper combination.
>The tonal compression that occurs is then a result of two curves - the one
>you did and the one implicit in the RIP calibration (the latter not
>visible).

One other perspective which ought to make you stop and think a little about
the current methodology.  Tyler has nicely espoused the current way of doing
things:  a desire for a nice linear (straight line) progression of density
from dMin to dMax across the full range of pixel values, 0-255 in 8 bit, 0-1
normalised.  So, for EEM for example, this would mean 0 maps to a density of
1.68 and 1 maps to a density of 0.04 and all other points in between sit on
the straight line between the two.  (If I am wrong on this please correct
me.)  In so doing you are defining (or calibrating) the colour space of the
printer.

NO COLOUR SPACE IN GENERAL USE TODAY HAS THIS SORT OF PROFILE. Not Apple
RGB, not Gray Gamma 1.8, not Adobe RGB, not Gray Gamma 2.2, not sRGB, not
LAB.  NONE of these are linear when we plot density vs pixel value.  ALL are
curved in this dimension, such curvature representing their gamma (a fancy
word for rate of change or contrast).  Plot them out.  You have all the
formulas.  Most have been covered in this thread and many are in general use
(eg we typically read LAB with our photospectrometers to then calculate the
density figures which are linearised above).  Those that aren't are covered
on Bruce's site and he even has calculators to make the job easier.

From what I can see (excuse the pun), making pixel value vs density plot as
a straight line has absolutely no basis in "colour" theory.  The only thing
that I have come across in photography that is linear in this dimension is
the measuring of light intensity by a photosensitive cell (a camera "pixel"
for example) and what is the first thing we do with this type of data?  We
apply a gamma, we curve the data.  Why?  Because the eye doesn't work in a
linear fashion in this dimension.  So I find it rather peculiar that people
on the one hand get obsessed with "how the eye sees" and yet, on the other,
ignore this when they make pixel value vs density linear.

The plot that more often than not is linear is log10(pixel value) vs
density!  ALL (with perhaps the exception of LAB, see my note below) the
colour spaces mentioned above ARE linear when we plot log10(pixel value) vs
density.  (As an aside, note that when Kodak plots the response curve of
photo paper it plots log10(exposure) vs density!) If you have a straight
line with pixel value vs density it is NOT linear when you then plot
log10(pixel value) vs density.

A note on LAB:  the LAB space may not provide a perfectly linear plot of
log10(pixel value) to density but it is very close.  If it did Bruce
Lindbloom would have known the gamma embedded in the LAB model.  Instead he
had to undertake an exercise to find which gamma best fit the LAB model.  He
came up with 2.2.

Hi Keith

My brain is starting to hurt on this stuff and I am about to ask Tyler if I
can borrow some of his Tylenol <g>

But I thought I would add a point which I made to Paul Roark offline that
has to do with step wedges, mid grey and differences of tonal range.  This
may have some relevance to your exercise.

The way step wedges are printed at the moment, we put dMax at one end and
dMin at the other and look for tonal change immediately.  (We also kind of
improperly label these by putting a 100 next to the black and 0 next to the
white.  This is because we are thinking in terms of ink rather than the
values of the space we are working in. In LAB 0 is pure black and 100 is
pure white.  But that is a different story.)

Assume for a minute that the printer perfectly replicates LAB's defined
change in density FROM DMIN TO DMAX.  If my printer can print from L=16 to
L=96 (dMax =1.68 to dMin =0.04) and I want to put this range down on paper
in 21 uniform increments of LAB then I have to ask it to print a step wedge
with L values of 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72,
76, 80, 84, 88, 92, 96.  Note the mid point is not L=50, but rather L=56.
If I am using say Epson Premium SemiGloss and can reproduce, say, from L=6
to L=96 and I want to print in equal steps of LAB then I have to print a
different series of L figures (6, 10.5, 15 etc) and the mid point here is
51. L=50 still prints at a density of 0.73 but this isn't necessarily the
mid point of the printer range.

Even if the printer RIP automatically automatically spaces LAB values from
dMin to dMax, ie 0 gets mapped to 16, 5 to 20 etc, you still end up with the
same result: the mid-point shifts.

(By the way, take a look at this sequence of co-ordinates, and their density
equivalents, and look how all print values are shifted.  Plot the step vs
density figures of the two papers and overlay LAB.  Even if the RIP doesn't
make this linear, as I believe was suggested, but curved in equal increments
of LAB, each paper has a different gamma and non have the same value or
curvature as LAB. Only as paper white moves closer to perfect white and ink
dMax approaches perfect black do the curves begin to converge and have the
same gamma.)

This reflects no other fact than I get can get better dMax on EPSG than EEM
or that the I have a more equal reach into black as into white.

So if you do curves or suchlike so that your step wedge always prints with
the 50 step print at L=50 then you are distorting one end of the scale.
What's more this curve will be different across papers. EPSG is more
balanced around L=50 than EEM, for example, and requires less distortion.

This whole setup gets awkward very fast.  You either have a shifting mid
point and a greater or lesser error from LAB or you have a fixed mid and
varying contortion to fix the mid.

With the setup I have proposed there is no error from LAB (or whatever you
want to calibrate to) over the dynamic range of the printer, L=50 always
sits in the middle of the step wedge, and to the left or right of it is LAB
until you hit the limit of the printer's dynamic range.  The corollary to
this is that just prior to printing I need to actively recognize the tonal
range of my printer vs the image.  If the image is all in range then I need
do nothing.  But most likely it was already, or manipulated such that, it
used the full tonal range of my workspace.  I can¹t print this tonal range.
I must now decide how to alter this range to fit within my printer range.
One simple curve.  If I don¹t shift the mid point, any part of the image
which I exposed to L=50=Kodak grey (and did not shift later) prints Kodak
grey.

I hope this helps.

Cheers

Steve

> From: Keith Douglas <kdouglas@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Tue, 07 Dec 2004 15:24:17 -0800
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Tonal range and linearization
> 
> 
> I'm on windows, so I don't have the luxury of using Roy's curve creation
> tools.  I've started from scratch with Excel and Matlab.  Here's an
> overview of what I've done so far (using UT1 on a 1280 btw):
> 
> Print K, C and LC step-wedges with (mathematically) linear transfer
> function for QTR.
> Measure dmax and gamma for each, create 1/gamma curves.  This roughly
> linearizes the output.
> Print K,C and LC step-wedges with my new 1/gamma curves.
> Measure each step on the step-wedge.  Fine-tune curve to give linear
> brightness from dmin to dmax for each ink.
> Partition these three inks to give overall linear brightness.
> 
> Here's where I've stopped before.  The output is very linear (except I'm
> still having trouble with the transitions between inks).  Middle grey is
> the exact middle between paper-white and ink-black.
> 
> Now what I'm thinking is adding an overall curve to first map (128,128,128)
> to Kodak middle-grey.  Then I'll adjust the slope of the curve to make the
> on-screen contrast the same as the
> printed-contrast.  What-I-see-is-what-I-get.
> 
> -Keith
> 
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> 
> One other perspective which ought to make you stop and think a
little about
> the current methodology.  Tyler has nicely espoused the current way
of doing
> things:  a desire for a nice linear (straight line) progression of
density
> from dMin to dMax across the full range of pixel values, 0-255 in 8
bit, 0-1
> normalised.  So, for EEM for example, this would mean 0 maps to a
density of
> 1.68 and 1 maps to a density of 0.04 and all other points in between
sit on
> the straight line between the two.  (If I am wrong on this please
correct
> me.)  In so doing you are defining (or calibrating) the colour space
of the
> printer....

Well, if I understand you, not exactly. I've never mentioned a
straight line. I have mentioned calibration to a selectable standard,
a concept about which we have been discussing proper nomenclature.
Roy has selected LAB, IJM has selected user selectable gamma 2.2 or
1.8 (someone correct me if I'm wrong). StudioPrint lets one select any
dot gain along a continuous line from 0 to 49%. I suppose 0% might
bear some relation to "linear", but as you suggest isn't very useful.
I wouldn't call this process having much to do with color spaces as we
think of them, but output density adjustment. Though obviosly the
process "defines" (measures) an uncalbrated output in order to
calibrate it, I wouldn't say we are conciously doing that the way icc
profiling does (accept those profiles made for soft proof, once
linearized). Calibration would be a better term, and if using a RIP
for color, profiling is then done after "calibration".
So again, I suspect we have a linguistics issue.
Also, possibly of interest-
When working with Photoshop gray scale spaces, notice that gamma and
dot gain are interchangeable. So I, for example, could just as easily
work in a 2.2 gamma gray space, and use an equivalent dot gain as my
target calibration in StudioPrint, and achieve the same thing as we
are now doing with a 20%dg space and a 20%dg linearization. Very
similar to Roy developing a LAB based gray space to work well with LAB
calibrated output. We chose 20% because it's a prepress standard and
commonly used.
Have I missed your point?
Tyler

I don't want to get caught up in semantics but really when we profile a
printer with say an Eye-One we aren't calibrating. We don't change anything
the printer does, we don't tweak the printer control.  Rather we _measure_
how the printer renders pixel values and hence simply profile it.  Colorsync
takes this profile and does all the mapping from one profile to the next -
altering pixel values as necessary.  When we do change how the printer acts
for a given pixel value, telling it to put down x ink, I would say we _are_
calibrating it (rather than profiling it).  That is why I used the term
calibration.

With regard to linearity, I clearly misunderstood you when you said:

"I need all those relationships to be proportionally maintained,
absolutely, and that is what I think is generally accepted as
linearization, even though that moniker may be incorrect by strict
definition."

Apologies.

Call it output density adjustment or anything else, you are defining what
density the printer will print for a given pixel value.  Typically
"linearization" refers to the last step in the process whereby the raw
instruction set developed from partitioning is refined to meet a particular
curvature in the pixel value vs density graph.  Do we agree on this?  I
think we do and this is good.

(I would suggest that the term came from the fact that for sRGB, Adobe RGB,
Apple RGB, Gray Gamma 1.8 and Gray Gamma 2.2 are all linear when log(pixel
value) is plotted against density as is any function where y=x^g g being the
gamma value.  So linearization meant fine tuning the curvature of the
printer output so that log(pixel value) plotted against density is a
straight line.)

Now we come to the question of whether or not we achieve the results we
intend. This is made up of two parts:  (a) did we get an even curvature such
that if we plotted the log of each side we would get a straight line (at
least over the dynamic range of the printer) and (b) is this the straight
line we were after.

I would suggest that when someone says I want to linearize to LAB, for
example, what they intend to achieve is a curvature of the pixel vs density
plot that matches the curvature of LAB.  What this would mean is that the
printer would reflect a change in density for a change in pixel value that
matches LAB, how the eye sees and all that good stuff.  If it doesn't then
we have failed to meet our goal.  If you say "well who cares if it doesn't"
then I would say "why reference your target to anything then, let alone
something which denotes a sense of rigour.  Pick any old number or target -
what the hell you can always soft proof the file and fix it with an edit."

So do we meet our target of linearizing to LAB?  Pick any paper and
associated curve, print the step wedge, measure the printed densities and
plot them versus those defined by LAB.  I can tell you now that they will
not be the same, they will only overlap right up near dMin, the midpoint
will not be 18% reflectance and that the chart will be different for each
ink/paper combo.  EPSG is closer than EEM but neither are "right".  Neither
will bear any resemblance to the LAB curve except they are all curved.  Each
will exhibit a lesser or greater degree of error from our target.  This
error is unnecessary.

With the methodology I am proposing they would all overlap LAB for the range
of density values able to be rendered by the printer.  And I get an added
bonus if I choose LAB: any part of my image where L=50 will always print
Kodak 18% reflectance grey.


Cheers

Steve

> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 08 Dec 2004 18:02:40 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] Re: Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
> <stevekale@b...> wrote:
>> 
>> One other perspective which ought to make you stop and think a
> little about
>> the current methodology.  Tyler has nicely espoused the current way
> of doing
>> things:  a desire for a nice linear (straight line) progression of
> density
>> from dMin to dMax across the full range of pixel values, 0-255 in 8
> bit, 0-1
>> normalised.  So, for EEM for example, this would mean 0 maps to a
> density of
>> 1.68 and 1 maps to a density of 0.04 and all other points in between
> sit on
>> the straight line between the two.  (If I am wrong on this please
> correct
>> me.)  In so doing you are defining (or calibrating) the colour space
> of the
>> printer....
> 
> Well, if I understand you, not exactly. I've never mentioned a
> straight line. I have mentioned calibration to a selectable standard,
> a concept about which we have been discussing proper nomenclature.
> Roy has selected LAB, IJM has selected user selectable gamma 2.2 or
> 1.8 (someone correct me if I'm wrong). StudioPrint lets one select any
> dot gain along a continuous line from 0 to 49%. I suppose 0% might
> bear some relation to "linear", but as you suggest isn't very useful.
> I wouldn't call this process having much to do with color spaces as we
> think of them, but output density adjustment. Though obviosly the
> process "defines" (measures) an uncalbrated output in order to
> calibrate it, I wouldn't say we are conciously doing that the way icc
> profiling does (accept those profiles made for soft proof, once
> linearized). Calibration would be a better term, and if using a RIP
> for color, profiling is then done after "calibration".
> So again, I suspect we have a linguistics issue.
> Also, possibly of interest-
> When working with Photoshop gray scale spaces, notice that gamma and
> dot gain are interchangeable. So I, for example, could just as easily
> work in a 2.2 gamma gray space, and use an equivalent dot gain as my
> target calibration in StudioPrint, and achieve the same thing as we
> are now doing with a 20%dg space and a 20%dg linearization. Very
> similar to Roy developing a LAB based gray space to work well with LAB
> calibrated output. We chose 20% because it's a prepress standard and
> commonly used.
> Have I missed your point?
> Tyler
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
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> unsubscribe, please edit your Membership preferences by visiting this same
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> 
> Please follow these basic guidelines:
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> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
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> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE ³OWNER² AND
> ³MODERATORS² OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  ³OWNER² AND ³MODERATORS² OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
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> DIGITAL BW, THE PRINT YAHOO GROUP.
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> Yahoo! Groups Links
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> 
> 
>  
> 
> 
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> I don't want to get caught up in semantics but really when we profile a
> printer with say an Eye-One we aren't calibrating. We don't change
anything
> the printer does, we don't tweak the printer control.  Rather we
_measure_
> how the printer renders pixel values and hence simply profile it. 
Colorsync
> takes this profile and does all the mapping from one profile to the
next -
> altering pixel values as necessary.  When we do change how the
printer acts
> for a given pixel value, telling it to put down x ink, I would say
we _are_
> calibrating it (rather than profiling it).  That is why I used the term
> calibration.

Of course, agreed to all.

> With regard to linearity, I clearly misunderstood you when you said:
> 
> "I need all those relationships to be proportionally maintained,
> absolutely, and that is what I think is generally accepted as
> linearization, even though that moniker may be incorrect by strict
> definition."
> 
> Apologies.
> 
> Call it output density adjustment or anything else, you are defining
what
> density the printer will print for a given pixel value.  Typically
> "linearization" refers to the last step in the process whereby the raw
> instruction set developed from partitioning is refined to meet a
particular
> curvature in the pixel value vs density graph.  Do we agree on this?  I
> think we do and this is good.

Yes, but "linearized", or "calibrated" to a selected standard, like
LAB, a dot gain, a gamma. I believe that was where the thread started,
which one, why, and whether the final output is in fact progressing by
that standard.

...
> Now we come to the question of whether or not we achieve the results we
> intend....
snip
> I would suggest that when someone says I want to linearize to LAB, for
> example, what they intend to achieve is a curvature of the pixel vs
density
> plot that matches the curvature of LAB.

...
and I thought we had concluded that that is indeed not what is
happening by the conventional use of the term.

> ...  What this would mean is that the
> printer would reflect a change in density for a change in pixel
value that
> matches LAB, how the eye sees and all that good stuff.  If it
doesn't then
> we have failed to meet our goal.  If you say "well who cares if it
doesn't"
> then I would say "why reference your target to anything then, let alone
> something which denotes a sense of rigour.  Pick any old number or
target -
> what the hell you can always soft proof the file and fix it with an
edit."

I don't think that is the case at all, there is clearly a usefulness
to selecting a target that is also the working space, and
"linearizing" by conventional standards referencing that target.
Clearly the resulting print bears a strong resemblance to the monitor
image, even without softproof.
That the entire curve has been proportionally compressed to match end
points clearly breaks from your particular goal, and a strict
technical definition of linearization to the selected standard, I'm
not arguing that.
I'd just like to use "clearly" in a sentence one more time.

I understand what you are after. All I am saying is that, despite it's
semantic inaccuracy, the conventional process works extraordinarily
well, is miles ahead of where we were before these tools were
available, and allows myself and others to achieve goals previously
barely attainable.

You are defining a different workflow and different end result, the
conventional approach to linearization may not be suitable for that as
you have been saying.

I'm sure my inconsistent use of terminology and ADD when it comes to
math is part of the problem here, I may not be the right guy to see
this conversation through. I suspect, though, that we are more or less
done and the approach I use, and the one so far used by many in the
community, is of little use to you.
I hope I haven't sounded like I'm trying to talk you into it, not at all.
I'd also add, in it's conceptual defense, that the craft (not the art)
of photography has always involved dealing with and/or matching the
range of the real world, through many steps and materials, down to the
range of a print. Scene to film, film to print, and now the same
concept in the digital realm with it's different steps along the way.
Not sure what more I have to offer here Steve, but I'll be watching
your progress with interest.
Tyler

Hi Steve,

There are quite a few different units floating around and many mathematical
formulas.  Just saying "linearize" is very ambiguous until you define exactly
what you are linearizing.  Nobody wants to linearize "density" values.  That 
would put the 50 step at about 0.86 midway between 0.04 and 1.68.   

I think we'd all agree that there has to be some sort of up sweeping curve
when you plot density.  But there are numerous mathematical functions that
exhibit this look but in fact are different when you get to the details of the shape.

I can think of three main physical values from color theory that are relevant:
Density,  the Y of XYZ which is luminance, and L of Lab called luminosity or
sometimes lightness.  The names sometimes get confused but the letters are
always consistently defined.

Mathematically they are related:
density = -log(Y)
Y = ((L+16)/116)^3   for L >=8
Y = L/903                  for L < 8

Gamma is a purely mathematical function:
output = input ^ gamma

Dot Gain is a physical property of putting ink onto paper which
typically gives a curved shape because the middle values are affected
more that the end points.

A finally the pixel values of 0-255 are totally arbitrary -- they may be derived
in any way we like.

All the functions above have a sweeping curve character.  When you start
combining them you have a unlimited number of possible shapes.
So any spec that quotes a particular shape really needs a lot of qualification
about what they really mean.

What QTR does and I advocate is linearizing in Lab values.  Lab was defined way
back in the early 1900's using large studies of human perception and our eye's
response to light intensities.  The weird function was designed to mimic the
way we see.  So when QTR linearizes to Lab values it just uses the dynamic range
of dMin to dMax to the "best" curve.

What has been the weak part is that we've been using the gray space of gamma
2.2 which has a different shape.  I'm always been a little surprised or annoyed that
I calibrate my monitor with the best gear but when I look at a 21step wedge the
dark shadows from 100 to 95 seem much more compressed that the rest of the
wedge.  Getting the soft proofing working has "fixed" this in the sense that I
can now get reasonable separation throught the 21step.

This whole thread has gotten me to figure out more of this.  The problem with our
scheme so far is the gamma 2.2 working space.  It just isn't geared to our perception.
It's close and if you look at Lindbloom's site about comparing Lab to gamma 2.2
you can see what's going on.  Lab doesn't have a "gamma" -- it has that cubic
equation.  Bruce has just shown that gamma 2.2 is pretty close.   But if you look at
the comparision though you'll notice a strange wiggle in the curve in the bottom
left corner.  This is the source of the compressed 100-95 levels.

This is why I've introduced the new gray space.  Whatever the gray space is, is
what gets converted to the monitor display space.  Now we have all the parts talking
the same language.  I've still got some tweaking to do since this was done more by
trial and error than mathematically.  But I think this may be a significant "new"
way to deal with B&W printing.

Roy


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale <stevekale@b...> 
wrote:

> 
> One other perspective which ought to make you stop and think a little about
> the current methodology.  Tyler has nicely espoused the current way of doing
> things:  a desire for a nice linear (straight line) progression of density
> from dMin to dMax across the full range of pixel values, 0-255 in 8 bit, 0-1
> normalised.  So, for EEM for example, this would mean 0 maps to a density of
> 1.68 and 1 maps to a density of 0.04 and all other points in between sit on
> the straight line between the two.  (If I am wrong on this please correct
> me.)  In so doing you are defining (or calibrating) the colour space of the
> printer.
> 
> NO COLOUR SPACE IN GENERAL USE TODAY HAS THIS SORT OF PROFILE. Not Apple
> RGB, not Gray Gamma 1.8, not Adobe RGB, not Gray Gamma 2.2, not sRGB, not
> LAB.  NONE of these are linear when we plot density vs pixel value.  ALL are
> curved in this dimension, such curvature representing their gamma (a fancy
> word for rate of change or contrast).  Plot them out.  You have all the
> formulas.  Most have been covered in this thread and many are in general use
> (eg we typically read LAB with our photospectrometers to then calculate the
> density figures which are linearised above).  Those that aren't are covered
> on Bruce's site and he even has calculators to make the job easier.
> 
> From what I can see (excuse the pun), making pixel value vs density plot as
> a straight line has absolutely no basis in "colour" theory.  The only thing
> that I have come across in photography that is linear in this dimension is
> the measuring of light intensity by a photosensitive cell (a camera "pixel"
> for example) and what is the first thing we do with this type of data?  We
> apply a gamma, we curve the data.  Why?  Because the eye doesn't work in a
> linear fashion in this dimension.  So I find it rather peculiar that people
> on the one hand get obsessed with "how the eye sees" and yet, on the other,
> ignore this when they make pixel value vs density linear.
> 
> The plot that more often than not is linear is log10(pixel value) vs
> density!  ALL (with perhaps the exception of LAB, see my note below) the
> colour spaces mentioned above ARE linear when we plot log10(pixel value) vs
> density.  (As an aside, note that when Kodak plots the response curve of
> photo paper it plots log10(exposure) vs density!) If you have a straight
> line with pixel value vs density it is NOT linear when you then plot
> log10(pixel value) vs density.
> 
> A note on LAB:  the LAB space may not provide a perfectly linear plot of
> log10(pixel value) to density but it is very close.  If it did Bruce
> Lindbloom would have known the gamma embedded in the LAB model.  Instead he
> had to undertake an exercise to find which gamma best fit the LAB model.  He
> came up with 2.2.

> From: Tyler Boley <tyler@...>

> 
> Yes, but "linearized", or "calibrated" to a selected standard, like
> LAB, a dot gain, a gamma. I believe that was where the thread started,
> which one, why, and whether the final output is in fact progressing by
> that standard.
> 

Good.  I think where differ is simply whether we achieve the goal of "the
final output is in fact progressing by that standard."  I initially started
the debate talking about whether we achieved a linearization/calibration to
Grey Gamma 2.2.  You highlighted the fact that perhaps LAB was better and
that this was the target chosen by QTR.  You note that the choice of target
is by no means without debate. I'll take your word on that.  I am simply
suggesting we don't get either with the present method.


> ...
>> Now we come to the question of whether or not we achieve the results we
>> intend....
> snip
>> I would suggest that when someone says I want to linearize to LAB, for
>> example, what they intend to achieve is a curvature of the pixel vs
> density
>> plot that matches the curvature of LAB.
> 
> ...
> and I thought we had concluded that that is indeed not what is
> happening by the conventional use of the term.

A curvature yes.  But what curvature and does the curvature meet the target?

> 
>> ...  What this would mean is that the
>> printer would reflect a change in density for a change in pixel
> value that
>> matches LAB, how the eye sees and all that good stuff.  If it
> doesn't then
>> we have failed to meet our goal.  If you say "well who cares if it
> doesn't"
>> then I would say "why reference your target to anything then, let alone
>> something which denotes a sense of rigour.  Pick any old number or
> target -
>> what the hell you can always soft proof the file and fix it with an
> edit."
> 
> I don't think that is the case at all, there is clearly a usefulness
> to selecting a target that is also the working space, and
> "linearizing" by conventional standards referencing that target.

Good.  Let's pick one and see if it works.

QTR picked LAB - I don't think it "works".

Not because it was the wrong target.  Simply because the output has not
achieved reference to target, in my opinion.  The density curve has
curvature and hence a gamma that isn't 1, but it isn't a LAB curve.
Furthermore, each paper curve has a different curve, different gamma.  This
is unnecessary.

> Clearly the resulting print bears a strong resemblance to the monitor
> image, even without softproof.
> That the entire curve has been proportionally compressed to match end
> points clearly breaks from your particular goal, and a strict
> technical definition of linearization to the selected standard, I'm
> not arguing that.
> I'd just like to use "clearly" in a sentence one more time.
> 
LOL!  Ok.

> I understand what you are after. All I am saying is that, despite it's
> semantic inaccuracy, the conventional process works extraordinarily
> well, is miles ahead of where we were before these tools were
> available, and allows myself and others to achieve goals previously
> barely attainable.

This I don't doubt.  I am simply suggesting that we can continue to move
forward.
> 
> You are defining a different workflow and different end result, the
> conventional approach to linearization may not be suitable for that as
> you have been saying.

In essence, yes.  I am suggesting that if we did achieve
linearization/calibration to target the workflow would simplify massively.
Soft proofing, for example, would become unnecessary.

> 
> I'm sure my inconsistent use of terminology and ADD when it comes to
> math is part of the problem here, I may not be the right guy to see
> this conversation through. I suspect, though, that we are more or less
> done and the approach I use, and the one so far used by many in the
> community, is of little use to you.

It is of great use to me.  I have printed some good prints using it.  But I
am suggesting that the workflow could be dramatically easier and the result
more precise.  I need either an Eye-One or access to another person's
soft-proof files and a lot of fiddling to get a sensible result that closely
matches my pre-print-phase image.

For example, as I said, soft proofing becomes unnecessary (except to proof
hue) and as a result the reintroduction of subjective matching of print
version to proofed version.

I very much like that this forum has endeavoured to make printing decent B&W
easier for people.  This I believe is a very worthy goal. I believe, quite
simply, that there is unnecessary complexity in the current workflow and
that if we achieved calibration to target this complexity would disappear in
one stroke.

> I hope I haven't sounded like I'm trying to talk you into it, not at all.
> I'd also add, in it's conceptual defense, that the craft (not the art)
> of photography has always involved dealing with and/or matching the
> range of the real world, through many steps and materials, down to the
> range of a print. Scene to film, film to print, and now the same
> concept in the digital realm with it's different steps along the way.

Yes.  I don't debate how that there are steps in the process.  I just don't
enjoy going 2 steps forward, 1 step back!

As I have said before, I don't have the necessary programming skills to
write my own RIP.  All I can do is suggest a simpler, more efficient way of
doing things and see if it gets adopted or ask Roy, as I have done in an
offline email, for some guidance as to how I might bend QTR to try to adopt
my revised workflow.  If I can't do that then I will stick with the status
quo and keep muddling on.

Have fun but don't keep striving forward...

:-)

Steve

Hi Roy


> From: Roy Harrington <roy@...>
 

> 
> There are quite a few different units floating around and many mathematical
> formulas.  Just saying "linearize" is very ambiguous until you define exactly
> what you are linearizing.  Nobody wants to linearize "density" values.  That
> would put the 50 step at about 0.86 midway between 0.04 and 1.68.
> 
> I think we'd all agree that there has to be some sort of up sweeping curve
> when you plot density.  But there are numerous mathematical functions that
> exhibit this look but in fact are different when you get to the details of the
> shape.
> 
> I can think of three main physical values from color theory that are relevant:
> Density,  the Y of XYZ which is luminance, and L of Lab called luminosity or
> sometimes lightness.  The names sometimes get confused but the letters are
> always consistently defined.
> 
> Mathematically they are related:
> density = -log(Y)
> Y = ((L+16)/116)^3   for L >=8
> Y = L/903                  for L < 8
> 
> Gamma is a purely mathematical function:
> output = input ^ gamma
> 

Yes I agree completely and have noted these formula in the earlier posts.


> Dot Gain is a physical property of putting ink onto paper which
> typically gives a curved shape because the middle values are affected
> more that the end points.
> 
> A finally the pixel values of 0-255 are totally arbitrary -- they may be
> derived
> in any way we like.
> 

Well I would say they are real, ie an image is made up of pixel values and
their respective location.  These values can be measured to varying degrees
of accuracy, eg 8 bit vs 16 bit, and presented in any way we like: 0-255,
0-1 etc

> All the functions above have a sweeping curve character.  When you start
> combining them you have a unlimited number of possible shapes.
> So any spec that quotes a particular shape really needs a lot of qualification
> about what they really mean.

Agreed.

> 
> What QTR does and I advocate is linearizing in Lab values.  Lab was defined
> way
> back in the early 1900's using large studies of human perception and our eye's
> response to light intensities.  The weird function was designed to mimic the
> way we see.  

Don't doubt this and I am prepared to follow CIE's results: go LAB!

> So when QTR linearizes to Lab values it just uses the dynamic
> range
> of dMin to dMax to the "best" curve.

Here is where I think we break down and have a key difference.  While you
use LAB values, you do not achieve a result that fits LAB.  This is the crux
of the matter that we need to explore.

> 
> What has been the weak part is that we've been using the gray space of gamma
> 2.2 which has a different shape.  I'm always been a little surprised or
> annoyed that
> I calibrate my monitor with the best gear but when I look at a 21step wedge
> the
> dark shadows from 100 to 95 seem much more compressed that the rest of the
> wedge.  Getting the soft proofing working has "fixed" this in the sense that I
> can now get reasonable separation throught the 21step.

Well I agree it is kind of silly to work in one space and print in another.
When I started this thread I bundled a lot of issues into the one topic.  We
are slowly separating these.  The issues I bundled together included at
least the issue of working in gamma 2.2 and "printing in LAB" (shorthand)
and whether in fact we "printed in LAB" in LAB as intended.
> 
> This whole thread has gotten me to figure out more of this.  The problem with
> our
> scheme so far is the gamma 2.2 working space.  It just isn't geared to our
> perception.

I will take your word on the perception side of things (go LAB!) but I think
there are two problems with "our scheme so far". The lesser one is the
"perception" problem of gamma 2.2.  The bigger issue is, I believe, we don't
actually "linearize to [our target] LAB".

> It's close and if you look at Lindbloom's site about comparing Lab to gamma
> 2.2
> you can see what's going on.  Lab doesn't have a "gamma" --

Almost yes.  I noted this in an earlier post.  It has a gamma but this is
not a single number - because it is a cubic function to begin its first
derivative is not a single value.

>it has that cubic
> equation.  Bruce has just shown that gamma 2.2 is pretty close.   But if you
> look at
> the comparision though you'll notice a strange wiggle in the curve in the
> bottom
> left corner.  This is the source of the compressed 100-95 levels.

Almost agreed.  The wiggle in 100-95 levels (L= 0-5) is outside our present
printing range.  Even with RC papers we can't print L=5.  This error is not
our primary problem.

> 
> This is why I've introduced the new gray space.  Whatever the gray space is,
> is
> what gets converted to the monitor display space.  Now we have all the parts
> talking
> the same language.  I've still got some tweaking to do since this was done
> more by
> trial and error than mathematically.  But I think this may be a significant
> "new"
> way to deal with B&W printing.

Well I need to think about this a bit further and I see you replied to my
other post which I will take a look at now.

Cheers

Steve

Steve, et al:

I've been following this thread and enjoyed the exchange of information. I 
have a few comments that, I believe, correspond to a few of things Tyler has 
been talking about. I’ll keep this as short as possible.

On the desktop we use software to control the behavior of hardware. With 
displays, for example, the machine is calibrated to known standards and a profile 
is then built that describes the color gamut and gamma of the device. Inkjet 
printers are linearized and although calibration and linearization perform 
similar functions, for their respective devices, they aren't the same thing. 
Displays aren't linearized. The calibration includes a gamma setting.

All image devices used in the digital darkroom—cameras, scanners, displays 
and, most important to this discussion, inkjet printers—include a gamma setting. 
As do analog film and printing paper. Gamma is built into imaging systems to 
account for human vision, which is anything but linear. In fact, you can think 
of gamma as an attempt to objectify our subjective experience of the world 
(which explains, in part, why we have different gamma settings to choose from in 
the digital domain).

Linearization controls the amount of ink used in each ink channel. The basic 
idea is to accurately map the image file information, including whatever gamma 
you've selected, to the printed surface. One of the issues with current OEM 
print drivers, which cannot be linearized, is that the image file gamma has to 
be mapped to the driver gamma bias. People like Paul Roark have done an 
amazing job of working through this issue.

With good software, linearization can be tweaked when necessary or desired 
(it just depends on how far you want to crack open the "black box"). Printer 
driver software, OEM or RIP, doesn't "care" what color space or profile is 
attached to an image file. It does care what gamma the image represents. It exists 
to manage the hardware functions of the machine and translate pixel information 
into droplets of ink.

Years ago, Kodak developed a methodology for mapping image density to code 
values, called the "Jones Plot". It addresses the issue of how image information 
is translated from one form into another. It’s useful to us because there 
are, in fact, significant semantic issues currently at play in the digital 
darkroom. In time, these issues will resolve themselves (talking about the 
translation of image information is a little like talking about resolution, where the 
same terminology is used to describe different things). 

Long story short (Ha!): if possible, it is best to work with a linearized 
inkjet printer. If a system is properly color managed you should be able to work 
with any conventional gamma setting offered through Photoshop's working modes 
(or build your own, including any variation of the LAB model) and produce 
prints that appropriately match the image on the display.


Bill Kennedy
Associate Professor of Photocommunications
St. Edward's University
512/448-8680


[Non-text portions of this message have been removed]

Hi Bill

Thanks for popping in.  I think we are talking here about things at a finer
level of detail.  The BIG issue with B&W printing today is that colour
management doesn't work to our satisfaction.  Hence we have for now
discarded it.  Boy, it would be easier if we didn't have to!  Here we are
talking about the finer points of how and to what extent do we want to align
(because we don't have a system for managing difference) our workspace and
print space, and how do we measure whether we have been successful.  (We
were also debating the somewhat side issue of just what those spaces should
be but I think we have settled on LAB as a good enough place for now.) I
think we agree that a linearized printer is best but we are discussing
"linearized in what fashion?".  The software we have is VERY tweakable and
so allows the debate.

Cheers

Steve

> From: <BKPhoto@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 8 Dec 2004 17:06:28 EST
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Re: Tonal range and linearization
> 
> 
> Steve, et al:
> 
> I've been following this thread and enjoyed the exchange of information. I
> have a few comments that, I believe, correspond to a few of things Tyler has
> been talking about. I’ll keep this as short as possible.
> 
> On the desktop we use software to control the behavior of hardware. With
> displays, for example, the machine is calibrated to known standards and a
> profile 
> is then built that describes the color gamut and gamma of the device. Inkjet
> printers are linearized and although calibration and linearization perform
> similar functions, for their respective devices, they aren't the same thing.
> Displays aren't linearized. The calibration includes a gamma setting.
> 
> All image devices used in the digital darkroom—cameras, scanners, displays
> and, most important to this discussion, inkjet printers—include a gamma
> setting. 
> As do analog film and printing paper. Gamma is built into imaging systems to
> account for human vision, which is anything but linear. In fact, you can think
> of gamma as an attempt to objectify our subjective experience of the world
> (which explains, in part, why we have different gamma settings to choose from
> in 
> the digital domain).
> 
> Linearization controls the amount of ink used in each ink channel. The basic
> idea is to accurately map the image file information, including whatever gamma
> you've selected, to the printed surface. One of the issues with current OEM
> print drivers, which cannot be linearized, is that the image file gamma has to
> be mapped to the driver gamma bias. People like Paul Roark have done an
> amazing job of working through this issue.
> 
> With good software, linearization can be tweaked when necessary or desired
> (it just depends on how far you want to crack open the "black box"). Printer
> driver software, OEM or RIP, doesn't "care" what color space or profile is
> attached to an image file. It does care what gamma the image represents. It
> exists 
> to manage the hardware functions of the machine and translate pixel
> information 
> into droplets of ink.
> 
> Years ago, Kodak developed a methodology for mapping image density to code
> values, called the "Jones Plot". It addresses the issue of how image
> information 
> is translated from one form into another. It’s useful to us because there
> are, in fact, significant semantic issues currently at play in the digital
> darkroom. In time, these issues will resolve themselves (talking about the
> translation of image information is a little like talking about resolution,
> where the 
> same terminology is used to describe different things).
> 
> Long story short (Ha!): if possible, it is best to work with a linearized
> inkjet printer. If a system is properly color managed you should be able to
> work 
> with any conventional gamma setting offered through Photoshop's working modes
> (or build your own, including any variation of the LAB model) and produce
> prints that appropriately match the image on the display.
> 
> 
> Bill Kennedy
> Associate Professor of Photocommunications
> St. Edward's University
> 512/448-8680
> 
> 
> [Non-text portions of this message have been removed]
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
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> 
> Please follow these basic guidelines:
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> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
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>

just between you and me, if I understand him correctly, I don't see
the point of Steve's proposed "linearization".
It just doesn't seem like a viable approach at all. You could achieve
the exact same thing with standard linearization. lets say to LAB in
QTR, and clip the file (in your LAB space) to the dmin & dmax L points
he's arrived at for his paper, and print.
Except for adhereing to some precise standard for the sake of
conversation, I don't get it. I gotta back out of this thread with
him, it goes in circles.
But I've been wrong before, so maybe I'm the one who's nuts...
T

In a message dated 12/8/04 4:51:07 PM, stevekale@... writes:

"The BIG issue with B&W printing today is that colour management doesn't work 
to our satisfaction.  Hence we have for now discarded it."

Wow. I'm not sure what you mean by "we". I use a color managed approach to 
grayscale (and color) printing and have no intentions of discarding it. It works 
very well.

Best of luck with the semantics. I'll be popping out now.

 
Bill Kennedy
Associate Professor of Photocommunications
St. Edward's University
512/448-8680


[Non-text portions of this message have been removed]

Sorry Steve, tired here. But do you see the idea of "standard"
linearization then clipping. Doesn't that get you there?
Again, my apologies, sheesh...
Forever the baffoon,
Tyler

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Tyler Boley"
<tyler@t...> wrote:

> 
> just between you and me, if I understand him correctly, I don't see
> the point of Steve's proposed "linearization".
> It just doesn't seem like a viable approach at all. You could achieve
> the exact same thing with standard linearization. lets say to LAB in
> QTR, and clip the file (in your LAB space) to the dmin & dmax L points
> he's arrived at for his paper, and print.
> Except for adhereing to some precise standard for the sake of
> conversation, I don't get it. I gotta back out of this thread with
> him, it goes in circles.
> But I've been wrong before, so maybe I'm the one who's nuts...
> T

Yes I agree that you don't see it but never mind.  No offence taken. But
standards are there to be updated.

> From: Tyler Boley <tyler@...m>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 08 Dec 2004 23:12:52 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] Re: Tonal range and linearization
> 
> 
> 
> just between you and me, if I understand him correctly, I don't see
> the point of Steve's proposed "linearization".
> It just doesn't seem like a viable approach at all. You could achieve
> the exact same thing with standard linearization. lets say to LAB in
> QTR, and clip the file (in your LAB space) to the dmin & dmax L points
> he's arrived at for his paper, and print.
> Except for adhereing to some precise standard for the sake of
> conversation, I don't get it. I gotta back out of this thread with
> him, it goes in circles.
> But I've been wrong before, so maybe I'm the one who's nuts...
> T
> 
> 
> 
> 
> 
> 
> Please visit the Group Homepage to check the Files, and other resources as
> they are often being updated.
> 
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint
> 
> If you wish to receive no emails or just a daily digest, or you wish to
> unsubscribe, please edit your Membership preferences by visiting this same
> page.
> 
> Please follow these basic guidelines:
> - As threads develop, trim off excess portions of earlier messages to keep
> them short.
> - Good manners are required at all time. No personal attacks or flames.
> Hostile, aggressive or argumentative users may be removed from the membership
> without notice.
> - Keep your posts and threads related to the group topic of digital B&W
> printing. Users who persistently make off-topic posts may be removed from the
> membership.
> - By posting on this forum you agree to abide by the group rules and
> guidelines, and to abide by the actions and decisions of the group Owner and
> Moderators. See ³Group Topic, Rules and Guidelines² in the Files section:
> http://groups.yahoo.com/group/DigitalBlackandWhiteThePrint/files/
> 
> BY PARTICIPATING IN AND/OR POSTING MESSAGES TO THE DIGITAL BW, THE PRINT
> YAHOO! GROUP YOU EXPRESSLY UNDERSTAND AND AGREE THAT THE ³OWNER² AND
> ³MODERATORS² OF DIGITAL BW, THE PRINT YAHOO GROUP SHALL NOT BE LIABLE TO YOU
> FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, CONSEQUENTIAL OR EXEMPLARY
> DAMAGES, INCLUDING BUT NOT LIMITED TO, DAMAGES FOR LOSS OF PROFITS, GOODWILL,
> USE, DATA OR OTHER INTANGIBLE LOSSES (EVEN IF THE  ³OWNER² AND ³MODERATORS² OF
> DIGITAL BW, THE PRINT YAHOO GROUP HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH
> DAMAGES), RESULTING FROM: (i) THE USE OR THE INABILITY TO USE THE DIGITAL BW,
> THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION OF YOUR
> TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD PARTY ON THE
> DIGITAL BW, THE PRINT YAHOO GROUP; OR (iv) ANY OTHER MATTER RELATING TO THE
> DIGITAL BW, THE PRINT YAHOO GROUP.
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
>

Steve, still, it had a rude tone and I'm extremely sorry. I've had a
good run on list for a bit, but given my longer term history I was
bound to step on my tongue at badly some point. I'm very sorry it
happened with you instead of someone perhaps actually deserving <G>.
This thread, sparked by your creative thinking, has been very valuable
no matter what it may lead to, and my participation has been willing
to say the least.
Please accept my apology, I learn every day.
Tyler

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> Yes I agree that you don't see it but never mind.  No offence taken. But
> standards are there to be updated.
> 
> 
> > From: Tyler Boley <tyler@t...>
> > Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > Date: Wed, 08 Dec 2004 23:12:52 -0000
> > To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> > Subject: [Digital BW] Re: Tonal range and linearization
> > 
> > 
> > 
> > just between you and me, if I understand him correctly, I don't see
> > the point of Steve's proposed "linearization".
> > It just doesn't seem like a viable approach at all. You could achieve
> > the exact same thing with standard linearization. lets say to LAB in
> > QTR, and clip the file (in your LAB space) to the dmin & dmax L points
> > he's arrived at for his paper, and print.
> > Except for adhereing to some precise standard for the sake of
> > conversation, I don't get it. I gotta back out of this thread with
> > him, it goes in circles.
> > But I've been wrong before, so maybe I'm the one who's nuts...
> > T
> > 
> > 
> > 
> > 
> > 
> > 
> > Please visit the Group Homepage to check the Files, and other
resources as
> > they are often being updated.
> > 
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³MODERATORS² OF
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POSSIBILITY OF SUCH
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> > THE PRINT YAHOO GROUP; (ii) UNAUTHORIZED ACCESS TO OR ALTERATION
OF YOUR
> > TRANSMISSIONS OR DATA; (iii) STATEMENTS OR CONDUCT OF ANY THIRD
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RELATING TO THE

> > DIGITAL BW, THE PRINT YAHOO GROUP.
> >  
> > Yahoo! Groups Links
> > 
> > 
> > 
> >  
> > 
> > 
> >

To keep a sense of perspective in this conversation, I ask some basic
questions:

1.  Do we agree that the need to "colour manage" (broadly defined) results
because two devices don't have the exact same colour space?  (In this case,
our image file on the computer and our printer)

2.  Do we agree that if our printer and our computer did share the same
colour space (or at least all the parts we care about) this whole
conversation would be redundant?

3. Do we agree that we have abandoned an automated method for managing the
difference between the two colour spaces (ie something like colorsync)?

4.  Do we agree that if our printer and our computer have overlapping colour
spaces that we would just have to decide what to do with the points that
didn't overlap and that such decision may or may not mean we decide to alter
the entire image to maintain a sense of relativity?

5.  Do we agree that more overlap is better than less?


I believe there is no reason for our workspace and printer not to share the
exact same "density" (which I will define as colour less hue) space for much
of the workspace range.  Specifically, for example, 16<=L=>96 for printing
to EEM and around 6<=L=>96 for printing on EPSG.

At the moment they share no common ground.  A simple image that is well
within the capability of the printer will not print properly out of the box
- instead it requires a _visual_ soft proof aid to get it to look right and
even then it may not print right.

If they did share the good proportion of common ground they are capable,
deciding what to do about of gamut values would be easy and very intuitive.
Because they don't it is complex and not obvious, requiring the use of a
soft proof and "fiddling to match".

This is all I am pressing on.

Tyler

Seriously no offence taken.  I have learnt an enormous amount from you and
others like you on this list.  I know this has been a grinding discussion.
Worse yet it is one which challenges conventional techniques and so was
always going to be a doozy.  On top of all that, it is a very very technical
discussion and hence one that is very difficult to conduct over email
without the benefit of even a diagram.  I am glad you persevered this far.

I hope that at a minimum this discussion has provoked thought and
introspection about current methodologies and perhaps educated a few people
about some of the concepts involved.

Roy is already working up a storm on the front end - the workspace.  I just
wish there was also a little consideration of getting the back-end (the
printer) a little closer also.  I don't think this is very hard and it is
readily achievable.

Cheers

Steve

> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Wed, 08 Dec 2004 23:30:03 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] Re: Tonal range and linearization
> 
> 
> 
> Steve, still, it had a rude tone and I'm extremely sorry. I've had a
> good run on list for a bit, but given my longer term history I was
> bound to step on my tongue at badly some point. I'm very sorry it
> happened with you instead of someone perhaps actually deserving <G>.
> This thread, sparked by your creative thinking, has been very valuable
> no matter what it may lead to, and my participation has been willing
> to say the least.
> Please accept my apology, I learn every day.
> Tyler
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> Tyler
> 
> Seriously no offence taken.

That's very generous of you and has made my afternoon.
I have some thoughts on the questions you raise in the other post and
will come back to them, for what it's worth.
Gotta get some work done!
Tyler

Like Tyler, I can't get my mind around the math stuff, but I've got a 
good logical mind and a good understanding of ICC color management.

I think I'll throw some thoughts out between the quote below.

-bruce


On Wednesday, Dec 8, 2004, at 20:36 US/Pacific, 
DigitalBlackandWhiteThePrint@yahoogroups.com wrote:

> Message: 4
>    Date: Wed, 08 Dec 2004 23:49:16 +0000
>    From: Steve Kale <stevekale@...>
> Subject: Re: Re: Tonal range and linearization
>
>
> To keep a sense of perspective in this conversation, I ask some basic
> questions:
>
> 1.  Do we agree that the need to "colour manage" (broadly defined) 
> results
> because two devices don't have the exact same colour space?  (In this 
> case,
> our image file on the computer and our printer)

Kind of. The most important aspect for both color and B&W is that the 
the display image and underlying data be standardized, or at least 
known and tagged as such. Photoshop takes care of that by having us 
work in standard (or at least defined) color and greyscale workspaces. 
The big trick being that a measured and profiled monitor (tagged) is 
used to display the image after conversion from the work space. 
Ensuring that what we see is accurate
>
> 2.  Do we agree that if our printer and our computer did share the same
> colour space (or at least all the parts we care about) this whole
> conversation would be redundant?

Yes.
>
> 3. Do we agree that we have abandoned an automated method for managing 
> the
> difference between the two colour spaces (ie something like colorsync)?

Not quite.

The issue with b&w is simply that the paper is darker than monitor 
white and the black (especially on matte paper) is much lighter than 
monitor black.

We don't need to "automate" this, as we already have the qtr curve set 
for a particular output. The question is what rules were used to create 
the curve.

In color, icc conversions have rules. I think that "relative 
colormetric" has a specific standardized rule to map out of gamut 
colors to their nearest neighbor. Simple enough, but this method often 
results in posterization when the printer space is way different (and 
smaller) than the working space.

So they came up with "perceptual intent" which uses some "voo doo" to 
make the print "feel" more like the original, just using the colors 
available in the printer.  This print will be much less accurate, but 
more pleasing. I don't think there is a standard "rule" for "perceptual 
intent". These rules are designed by the programer of the profiling 
software. Each profiling package will produce a different "perceptual 
intent" where the rules have been made by different programers. What 
these rules are, are compromises to make a pleasing print (in someone's 
opinion) when the printer can't reproduce what's in the original file. 
What I've found is that this works well for many images, and lousy for 
others. Sometimes the compromise is so severe where the printer just 
can't make a good print (with a particular paper and ink) that I've 
converted color photos to black and white just to get good tonality in 
the print. An example being a dark red brick building that my 6 ink 
epson can not reproduce in color without loosing all red in the darker 
bricks. In b&w I can see all the bricks in the same color!

I guess my point is that "automated" is in the eye of the beholder. 
Either the programmer of the profiling package, or the creator of the 
qtr curve, or Roark curve has a say. It's not just an automated box 
with scientific rules.

And many profiles are "edited" by eye after creation. Should the rules 
be sufficient, this would be uncommon, but it's not at all.
>
> 4.  Do we agree that if our printer and our computer have overlapping 
> colour
> spaces that we would just have to decide what to do with the points 
> that
> didn't overlap and that such decision may or may not mean we decide to 
> alter
> the entire image to maintain a sense of relativity?

One cannot simply leave all in gamut shades as is, and change only 
those out of gamut shades. In b&w this would just result in clipping 
the blackest and whitest tones because bringing only out of gamut 
shades into gamut would mean making them the same tone as tones already 
used by other tonal values. Making black the same tone as dark grey is 
the same as clipping as the change in density on the print would be 
invisible. It does make sense to change the black and out of gamut 
tones to in gamut tones as long as one changes ALL the tones in the 
print.
>
> 5.  Do we agree that more overlap is better than less?
>
>
> I believe there is no reason for our workspace and printer not to 
> share the
> exact same "density" (which I will define as colour less hue) space 
> for much
> of the workspace range.  Specifically, for example, 16<=L=>96 for 
> printing
> to EEM and around 6<=L=>96 for printing on EPSG.

#5 makes no sense to me. They are not close to the same space. A 
partial overlap is irrelevant.
>
> At the moment they share no common ground.  A simple image that is well
> within the capability of the printer will not print properly out of 
> the box
> - instead it requires a _visual_ soft proof aid to get it to look 
> right and
> even then it may not print right.

I think the visual soft proof aid is essential here. It is essential 
for color work where one uses a colorsync (ICC) workflow as well. I 
think the simple answer is that most images are not within the 
capability of the printer, and must be altered for printing acceptably. 
I think that your frustration Steve is that you are trying to make a 
matte watercolor paper print look like a glossy print. No conversion of 
data can make this so.
>
> If they did share the good proportion of common ground they are 
> capable,
> deciding what to do about of gamut values would be easy and very 
> intuitive.
> Because they don't it is complex and not obvious, requiring the use of 
> a
> soft proof and "fiddling to match".

By compressing all the working space gamut into the printer gamut using 
a QTR curve, or other method, we have essentially created a b&w 
conversion using our own "perceptual intent". The soft proof is the 
best, and only way, I can think of to make a visual match from screen 
to print. In fact it solves the whole "print matching" issue provided 
that the ink separation curves are working to separate all the tones 
(within reason).
>
> This is all I am pressing on.
>
Of course if anyone out there makes a great discovery, I'm all for it!

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
<stevekale@b...> wrote:
> 
> To keep a sense of perspective in this conversation, I ask some basic
> questions:

Steve, I'm leaving town and won't be able to get into this for at
least a week. I'd like to continue as there are still some disconnects.
So don't take my absence as a lack of interest.
I hope to be able to catch up later, I may be able to slip in a few
comments over the nest few days, but not the depth it deserves.
Best,
Tyler

OK thanks Tyler.  In the interim I am writing up my thoughts in a Word doc
with charts that help explain things.

> From: Tyler Boley <tyler@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 09 Dec 2004 16:41:40 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] Re: Tonal range and linearization
> 
> 
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, Steve Kale
> <stevekale@b...> wrote:
>> 
>> To keep a sense of perspective in this conversation, I ask some basic
>> questions:
> 
> Steve, I'm leaving town and won't be able to get into this for at
> least a week. I'd like to continue as there are still some disconnects.
> So don't take my absence as a lack of interest.
> I hope to be able to catch up later, I may be able to slip in a few
> comments over the nest few days, but not the depth it deserves.
> Best,
> Tyler

Steve-

I'm also going to be out of pocket for while. Won't be checking email until late next week. But I'd like to be included on your list when the materials you are preparing are available.

Bill Kennedy
Austin, Texas