Digital BW, The Print

I have an Epson 2100 printer that I want to use for best possible bw printing on matte 
papers.

Can anyone comment on the differences in quality / output between MIS UT-7 and PiezoTone 
K7 ? 

I dont need variable tone, only neutral / warm neutral.

B

bjornaagedk wrote:

> I have an Epson 2100 printer that I want to use for best possible bw 
> printing on matte
> papers.
>
> Can anyone comment on the differences in quality / output between MIS 
> UT-7 and PiezoTone
> K7 ?
>
> I dont need variable tone, only neutral / warm neutral.
>
> B

My reading is, if you need neutral *and* warm, then your choice is the 
variable tone UT-7 inkset. If on the other hand you want a fixed tone 
inkset, then K7 has one and only tone.

If you match exactly the tone of the K7 with the UT-7, I suspect that 
you'd be very hard pressed indeed to tell which print is which. But 
then, I've never done such a test.
--
Bruce Watson.

If tone to tone are the same, then compare ink price. But I doubt that 
you could achieve that tone conformity. According to reports posted 
here, MIS inkset produces better contrast.

> My reading is, if you need neutral *and* warm, then your choice is 
the 
> variable tone UT-7 inkset. If on the other hand you want a fixed 
tone 
> inkset, then K7 has one and only tone.
> 
> If you match exactly the tone of the K7 with the UT-7, I suspect 
that 

> you'd be very hard pressed indeed to tell which print is which. But 
> then, I've never done such a test.
> --
> Bruce Watson.
>

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, hogarth@s... wrote:

> My reading is, if you need neutral *and* warm, then your choice is the 
> variable tone UT-7 inkset. If on the other hand you want a fixed tone 
> inkset, then K7 has one and only tone.

Its actually quite different than that. Sorry if we did not do a good job communicating how 
K7 works. Each of the seven pure-carbon dilutions is separately formulated to be perfectly 
neutral. However, it was designed as a toning system. It differs from UT-7 and MediaStreet 
and Septone and CavePaint, because all seven of the K7 dilutions are used to print the 
tonal scale. The others use the warm side, or the cool side, or some blending of color 
tones into gray tones to create one of their variable tones.

What we presented with K7 is a way to take advantage of 7 or more ink channels - which 
gives much greater resolution detail, smoother crossovers, and better highlights. But 
achromatic ink, because it has no color, allows the color of the paper to create the final 
tone. For example, printing on Bradford Brilliant White produces Selenium Tone; printing 
on Hahnemuhle Photo Rag produces a neutral; and printing on Innnova Cold Press Art 
produces a warm neutral. Yet there are many shades in between and around these. K7 is 
actually a variable tone system - but done with a unique concept: via the paper, rather 
than a dual or multi-toning ink set

Being achromatic removes any possibility of metamerism, and of course there is no 
possibility of unwanted color modulation. The end result is that K7 melds into the paper 
and this allows its very, very photographic look.

I think its the word "Neutral" that throws people off. We can print Neutral. But thats only 
one tone of what we can print.  Of course, the other systems can really hit extremes 
towards blue and brown which K7 can't. We focused more for looks familiar to darkroom 
printers.


Jon Cone

Hello Jon,

>K7 is actually a variable tone system - but done with a unique 
>concept: via the paper, rather than a dual or multi-toning ink 
>set.

It's hardly a unique concept (meaning K7 is neither the first nor the
only system to use it).  People printing with the Black Only method
have been using and discussing this multi-tone approach for years. 
However we never patented it so you are welcome to use it without
paying us any royalties :)   

I agree that it is a pleasing way to print.  BO with Eboni has always
produced beautiful pure tones without any of the coloration that is
often seen with toned inks.  

I'm curious as to how the K7 inks are neutralized (because pure carbon
by itself on PR is moderately warm).  Did you use some cool toner? 
Many thanks.

Regards,
Clayton


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

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Clayton Jones" <cj@c...> wrote:
>
> Hello Jon,
> 
> It's hardly a unique concept (meaning K7 is neither the first nor the
> only system to use it).  People printing with the Black Only method
> have been using and discussing this multi-tone approach for years. 
> However we never patented it so you are welcome to use it without
> paying us any royalties :)  


Clayton,

Multi-toning was not the unique concept I was trying to communicate. Multi-toning is old 
as the hills. Maybe older! I agree to that. My first quad systems used multi-toning in both 
the early and mid 1990s.  Achromatic is the unique concept. Even EPSON 'black ink only' is 
not achromatic. Having seven achromatic ink dilutions combines color toning with higher 
fidelity - and that is the concept behind K7. If you're happy with black ink only K7 will be 
overkill to you. And no royalties due either of us!  ;^)

> I'm curious as to how the K7 inks are neutralized (because pure carbon
> by itself on PR is moderately warm).  Did you use some cool toner? 
> Many thanks.

Carbon is usually thought of as a warm only grade pigment. Carbon Sepia PiezoTone is an 
example of a pure carbon ink without color toners and it is very warm. But its not that 
unusual in other industries to see carbon used for its cool properties. How carbon will 
eventually appear to the eye is connected to how the carbon is treated for various 
purposes. Changing the size and shape of an individual pigment particle for example.... 
But there are also different grades of carbon pigment - so combine just these two 'how 
tos' and you may have an idea of the rich possibilities of treating carbon. Nano-technology 
combined with carbon allows it. But still it was very very difficult because the seven 
dilutions required seven distinct formulations, instead of making some mother conc and 
then diluting the mother conc. Hope that answers your curiosity.

best regards,

Jon

Hello Jon,

>Carbon is usually thought of as a warm only grade pigment. 
>Carbon Sepia PiezoTone is an example of a pure carbon ink 
>without color toners and it is very warm. But its not that 
>unusual in other industries to see carbon used for its cool 
>properties. How carbon will eventually appear to the eye is 
>connected to how the carbon is treated for various purposes. 
>Changing the size and shape of an individual pigment particle 
>for example....But there are also different grades of carbon 
>pigment - so combine just these two 'how tos' and you may have 
>an idea of the rich possibilities of treating carbon. 
>...Hope that answers your curiosity.

Very interesting, thank you.  It seems you are saying that carbon
does't necessarily have to be so warm.  If that's the case then why
have we been struggling for years to cool it?  Are we just now
figuring out how to manipulate it on this level?

Regards,
Clayton


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

And that is a very interesting question in itself.


john

> Very interesting, thank you.  It seems you are saying that carbon
> does't necessarily have to be so warm.  If that's the case then why
> have we been struggling for years to cool it?  Are we just now
> figuring out how to manipulate it on this level?
> 
> Regards,
> Clayton
> 
> 
> Info on black and white digital printing at    
> http://www.cjcom.net/digiprnarts.htm
>

Hello...I am a hobby photographer but get the occasional  
job......most often musicians promo shots, and pictures of bands and  
vocalists....these usually are requested to be in Black and white, so  
that is how I got into digital B/W. I have learned a LOT from this  
group especially from paul roark and clayton jones. Right now I am  
totally satisfied with my 2400 and epson papers like VFA, premium  
semi-matte, semi-gloss, premium luster and for 4x6 prints, premium  
glossy.

Now I wonder if there is a best image size for a given paper size. I  
have many prints in 16x20 frames.  Some of the images are 12x16, and  
some are 11x14.....is there a standard image size for a 16x20 frame?

Also, for promo shots, should it always be 8x10 (4:5 ratio) or can  
they be at the 2:3 ratio in portrait mode? would they then be 6x9 on  
a letter size sheet? I just made several prints for someone and  
instead of cropping I just left them full frame and printed 6x9 in  
portrait orientation. (I took the shots today, and he needed them the  
same day for printing in a program for a concert series) I am  
surprised that I like them as well as 8x10, or maybe even better than  
8x10. I wonder if the graphics people are going to be bothered by the  
2:3 ratio.

Are there solid rules of practice regarding this stuff? Is there a  
resource, like a website or group that I could check out? Thanks  
again for all the help over the last couple of years. Have a good  
one...... Doug M

> Also, for promo shots, should it always be 8x10 (4:5 ratio) 
> or can they be at the 2:3 ratio in portrait mode? would they 
> then be 6x9 on a letter size sheet?

I always thought that advertising shots were 6x9.

Chris


-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.

Hi everybody, I'm new to the list - my fist post. I haven't bought my quad
tone system yet and I'm still looking around. All I can say is that I have
extensive knowledge in the old darkroom techniques and I'm a fan of neutral
prints.

> Are we just now
>> figuring out how to manipulate it on this level?

The approach of Piezography seems to me (for what I've studied on the web
and on this list in the past 5 weeks) as the best system for somebody like
me who wants complete neutrality.

I think (my personal opinion) that it is this very neutrality which makes
"Black-and-White" into what it is and what it stands for.

Therefore I have never understood why people go into Quad Black and White
printing with all the investment involved and going about exchanging ink
cartridges and so on (even having a second dedicated printer for this) --
only to come up with Sepia or Blueish prints ?!

Question of taste, bien sûr.

On the topic of this thread, I can totally understand that (for the trained
eye) that the Paper plays in deed a role on the output - important for
maintaining consistency in a pure black and white portfolio book. That's
what I've experienced in the analog/chemical world and this is even true for
simple office paper!

Jon, you mentioned some paper brands and their effects on color hue even
when using total neutral ink sets like K7...

Question: Are there other paper brands / recommendations or can somebody
point me to a web site that reviews paper brands?

Thanks everybody for this high level and unique mailing list :-)


Martin  


http://www.martinmuntenbruch.com

Hi Doug;

The standard promo shot has for many yaers been the 8x10 glossy, 
probably because that was just the standard photo paper size. A 6x9 
on letter size looks quite nice as well, it gives it a nice matted 
look. In the end, it depends on how they're going to be used. If 
they are going to be reproduced, you probably shouldn't even be 
giving them prints, because digital printer artifacts like 
microbanding or a not-random enough dither pattern may cause 
interference patterns (moire) with the half-tone screens used for 
offset printing. If its possible you should talk to the printer 
involved, and ask if he's having any problems with it. At the very 
least I would check the finished product and verify its OK.

Steve Karafyllakis


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, Douglas 
meeuwsen <lipshurt@m...> wrote:
>
> Hello...I am a hobby photographer but get the occasional  
> job......most often musicians promo shots, and pictures of bands 
and  
> vocalists....these usually are requested to be in Black and white, 
so  
> that is how I got into digital B/W. I have learned a LOT from 
this  
> group especially from paul roark and clayton jones. Right now I 
am  
> totally satisfied with my 2400 and epson papers like VFA, premium  
> semi-matte, semi-gloss, premium luster and for 4x6 prints, 
premium  
> glossy.
> 
> Now I wonder if there is a best image size for a given paper size. 
I  
> have many prints in 16x20 frames.  Some of the images are 12x16, 
and  
> some are 11x14.....is there a standard image size for a 16x20 
frame?
> 
> Also, for promo shots, should it always be 8x10 (4:5 ratio) or 
can  
> they be at the 2:3 ratio in portrait mode? would they then be 6x9 
on  
> a letter size sheet? I just made several prints for someone and  
> instead of cropping I just left them full frame and printed 6x9 
in  
> portrait orientation. (I took the shots today, and he needed them 
the  
> same day for printing in a program for a concert series) I am  
> surprised that I like them as well as 8x10, or maybe even better 
than  
> 8x10. I wonder if the graphics people are going to be bothered by 
the  
> 2:3 ratio.
> 
> Are there solid rules of practice regarding this stuff? Is there 
a  

> resource, like a website or group that I could check out? Thanks  
> again for all the help over the last couple of years. Have a good  
> one...... Doug M
>

Can anyone tell me how to convert an L* measurement from an Eye1 device to a
D value? 

TonyR

Excel functions

For Density to L
=IF(Density<=2.05274,116*((10^(-1*Density))^(1/3))-16,116*(((903.3*10^(Densi
ty*-1)+16)/116))-16)

For L to density
=IF(LAB_L>=8,LOG(((LAB_L+16)/116)^3)*-1,LOG(LAB_L/903.3)*-1)

Best regards,
John Moody

-----Original Message-----
From: DigitalBlackandWhiteThePrint@yahoogroups.com
[mailto:DigitalBlackandWhiteThePrint@yahoogroups.com]On Behalf Of Tony Riley
Sent: Sunday, October 30, 2005 8:09 AM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: [Digital BW] Black Density measurement

Can anyone tell me how to convert an L* measurement from an Eye1 device to a
D value?

TonyR





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

I'm sure I need to thank you for your prompt response, John,
But you may not be surprised to know that you've thrown good info at a
phillistine!

I do have excel but how do I set up the conversion?

And just as a taster what would an L* value of 14 equate to?

Interesting stuff for a Sunday afternoon !

Tony R

> John Moody wrote:

> Excel functions

> For Density to L
> 
> =IF(Density<=2.05274,116*((10^(-1*Density))^(1/3))-16,116*(((903.
> 3*10^(Densi
> 
> ty*-1)+16)/116))-16)

> For L to density
> 
> =IF(LAB_L>=8,LOG(((LAB_L+16)/116)^3)*-1,LOG(LAB_L/903.3)*-1)

Well, LAB_L is a cell name; you can read about names in the user guide if
you wish.

Try this, paste the following into cell B1.
=IF(A1>=8,LOG(((A1+16)/116)^3)*-1,LOG(A1/903.3)*-1)

Now if you put 14 in A1, you should see 1.762 show up in B1.

John

-----Original Message-----
From: DigitalBlackandWhiteThePrint@yahoogroups.com
[mailto:DigitalBlackandWhiteThePrint@yahoogroups.com]On Behalf Of Tony Riley
Sent: Sunday, October 30, 2005 8:38 AM
To: digitalblackandwhitetheprint@yahoogroups.com
Subject: RE: [Digital BW] Black Density measurement

I'm sure I need to thank you for your prompt response, John,
But you may not be surprised to know that you've thrown good info at a
phillistine!

I do have excel but how do I set up the conversion?

And just as a taster what would an L* value of 14 equate to?

Interesting stuff for a Sunday afternoon !

Tony R






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

Thank you kind sir......

TonyR

On 30/10/2005 13:59:02, digitalblackandwhitetheprint@yahoogroups.com wrote:
> Well, LAB_L is a cell name; you can read about names in the user guide if
> 
> you wish.
> 
> 
> 
> Try this, paste the following into cell B1.
> 
> =IF(A1>=8,LOG(((A1+16)/116)^3)*-1,LOG(A1/903.3)*-1)
> 
> 
> 
> Now if you put 14 in A1, you should see 1.762 show up in B1.
> 
> 
> 
> John

Tony

It's worth understanding this in two steps.  Density is a log function of
luminance.  Log functions are simply nice because they turn curves into
straight lines.  In 1931 the Commission Internationale de l'Eclairage
standards body developed the CIE XYZ colour space is their best attempt to
represent the eye's reaction to light and the Y component/axis models the
average luminance function of the eye's cones.

The formulae you have been presented with do two things in one step.  They
convert CIELab's L* (the Lab colour space is a perceptually uniform colour
space) to CIE YYZ's Y.  From there you get to density by taking the log of
XYX_Y (ie the log of luminance).  The last thing is to multiply by -1
because it is reflective rather than emmissive.

So first you need to get from L* to XYZ_Y:

If L*>7.9996248 (or >8) then:

XYZ_Y = ((L*+16)/116)^3

Else

XYZ_Y = L* x 27/24389

And once you have XYZ_Y then

Density = -LOG(XYZ_Y)

Of course your EyeOne also gives you the XYZ_Y directly depending on the
manner in which it is used.

Unless I am mistaken, John needs to check the second part of the equation he
gave you.

Cheers

Steve

> From: John Moody <moodymz3@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Sun, 30 Oct 2005 08:59:02 -0500
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Black Density measurement
> 
> Well, LAB_L is a cell name; you can read about names in the user guide if
> you wish.
> 
> Try this, paste the following into cell B1.
> =IF(A1>=8,LOG(((A1+16)/116)^3)*-1,LOG(A1/903.3)*-1)
> 
> Now if you put 14 in A1, you should see 1.762 show up in B1.
> 
> John
> 
> -----Original Message-----
> From: DigitalBlackandWhiteThePrint@yahoogroups.com
> [mailto:DigitalBlackandWhiteThePrint@yahoogroups.com]On Behalf Of Tony Riley
> Sent: Sunday, October 30, 2005 8:38 AM
> To: digitalblackandwhitetheprint@yahoogroups.com
> Subject: RE: [Digital BW] Black Density measurement
> 
> I'm sure I need to thank you for your prompt response, John,
> But you may not be surprised to know that you've thrown good info at a
> phillistine!
> 
> I do have excel but how do I set up the conversion?
> 
> And just as a taster what would an L* value of 14 equate to?
> 
> Interesting stuff for a Sunday afternoon !
> 
> Tony R
> 
> 
> 
> 
> 
> 
> [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 „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, I approximated 27/24389 as 1/903.3.  That and using 8 rather than 7.9996248 gives errors around the 5th decimal place.
I had cobbled that function together some time ago.  Yours, and the function Tom Moore coded in VBA are much elegant, and what I would use for new work.
 
Best regards,
John Moody

-----Original Message-----
From: DigitalBlackandWhiteThePrint@yahoogroups.com [mailto:DigitalBlackandWhiteThePrint@...m]On Behalf Of Steve Kale
Sent: Sunday, October 30, 2005 9:31 AM
To: DigitalBlackandWhiteThePrint@yahoogroups.com
Subject: Re: [Digital BW] Black Density measurement
 
Tony

It's worth understanding this in two steps.  Density is a log function of
luminance.  Log functions are simply nice because they turn curves into
straight lines.  In 1931 the Commission Internationale de l'Eclairage
standards body developed the CIE XYZ colour space is their best attempt to
represent the eye's reaction to light and the Y component/axis models the
average luminance function of the eye's cones.

The formulae you have been presented with do two things in one step.  They
convert CIELab's L* (the Lab colour space is a perceptually uniform colour
space) to CIE YYZ's Y.  From there you get to density by taking the log of
XYX_Y (ie the log of luminance).  The last thing is to multiply by -1
because it is reflective rather than emmissive.

So first you need to get from L* to XYZ_Y:

If L*>7.9996248 (or >8) then:

XYZ_Y = ((L*+16)/116)^3

Else

XYZ_Y = L* x 27/24389

And once you have XYZ_Y then

Density = -LOG(XYZ_Y)

Of course your EyeOne also gives you the XYZ_Y directly depending on the
manner in which it is used.

Unless I am mistaken, John needs to check the second part of the equation he
gave you.

Cheers

Steve




> From: John Moody <moodymz3@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Sun, 30 Oct 2005 08:59:02 -0500
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Black Density measurement
> 
> Well, LAB_L is a cell name; you can read about names in the user guide if
> you wish.
> 
> Try this, paste the following into cell B1.
> =IF(A1>=8,LOG(((A1+16)/116)^3)*-1,LOG(A1/903.3)*-1)
> 
> Now if you put 14 in A1, you should see 1.762 show up in B1.
> 
> John
> 


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

BTW you can see from the formula below why people say L* is roughly the cube
root of luminance.  Luminance, XYZ_Y, can range from 0 to 1 and so for most
L*:

L* = XYZ_Y^(1/3) x 116 - 16

And you get very close with just L*=XYZ_Y^(1/3)

> From: Steve Kale <stevekale@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Sun, 30 Oct 2005 14:30:58 +0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Conversation: [Digital BW] Black Density measurement
> Subject: Re: [Digital BW] Black Density measurement
> 
> Tony
> 
> It's worth understanding this in two steps.  Density is a log function of
> luminance.  Log functions are simply nice because they turn curves into
> straight lines.  In 1931 the Commission Internationale de l'Eclairage
> standards body developed the CIE XYZ colour space is their best attempt to
> represent the eye's reaction to light and the Y component/axis models the
> average luminance function of the eye's cones.
> 
> The formulae you have been presented with do two things in one step.  They
> convert CIELab's L* (the Lab colour space is a perceptually uniform colour
> space) to CIE YYZ's Y.  From there you get to density by taking the log of
> XYX_Y (ie the log of luminance).  The last thing is to multiply by -1
> because it is reflective rather than emmissive.
> 
> So first you need to get from L* to XYZ_Y:
> 
> If L*>7.9996248 (or >8) then:
> 
> XYZ_Y = ((L*+16)/116)^3
> 
> Else
> 
> XYZ_Y = L* x 27/24389
> 
> And once you have XYZ_Y then
> 
> Density = -LOG(XYZ_Y)
> 
> Of course your EyeOne also gives you the XYZ_Y directly depending on the
> manner in which it is used.
> 
> Unless I am mistaken, John needs to check the second part of the equation he
> gave you.
> 
> Cheers
> 
> Steve
>

Duh of course - my mistake not yours.

> From: John Moody <moodymz3@yahoo.com>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Sun, 30 Oct 2005 09:48:47 -0500
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: RE: [Digital BW] Black Density measurement
> 
> Hi Steve, I approximated 27/24389 as 1/903.3.  That and using 8 rather than
> 7.9996248 gives errors around the 5th decimal place.
> I had cobbled that function together some time ago.  Yours, and the function
> Tom Moore coded in VBA are much elegant, and what I would use for new work.
>  
> Best regards,
> John Moody
>

Anyway Tony I gave you the longer version because I think it is worth
understanding what you are doing with the formula.  For the longest time I
simply had the formula in a spreadsheet and used it without comprehension.
When I finally understood what I was doing more than a few light bulbs went
off in relation to other stuff I had read etc.

Thanks both to you and John Moody for setting me off on the right path.
I have the Eye1 Pro and am using the Eye1 Share package to measure colour
patches but it is inevitably a long learning curve from producing working
profiles to understanding exactly what is going on "under the bonnet".

The reason for my request was that I am testing various papers to see which
give the richest(most dense) black. I am quite surprised at the range and
just how poor even some gloss papers are at good black reproduction.

Given that there is a fairly constant translation formula between L* and
Density why is D considered preferable to L as a unit of definition?

Any good books out there that might make a good read in the bath? <grin>

TonyR

 

Steve Kale kindly volunteered:

> Anyway Tony I gave you the longer version because I think it is worth
> 
> understanding what you are doing with the formula.  For the longest time
> I
> 
> simply had the formula in a spreadsheet and used it without comprehension.
> 
> 
> When I finally understood what I was doing more than a few light bulbs
> went
> 
> off in relation to other stuff I had read etc.

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Tony Riley" <listsubs@a...> 
wrote:
>
> Can anyone tell me how to convert an L* measurement from an Eye1 device to a
> D value? 
> 
> TonyR
>


Hi Tony.... you can go to this website

http://www.brucelindbloom.com/

and select CALC in the menu buttons and then select "Companding Calculator" from the 
next page.  You will then find that you can do L to density conversions from there.

Ed

I just tend to use L* (and not density) in thinking about how black or white
something is.  But there are reasons why density is worth knowing.  If you
plot the log function you see immediately that its shape is characteristic
of the eye's response to increasing light intensity.  Also, one unit on a
log10 scale is 3.32 exposure zones.  So if you know dMin and dMax then you
have a sense for how many f-stops of dynamic range you have.  The best
reading I have found for this stuff is Normen Koren's site:

http://www.normankoren.com/

Particularly the sections on "Monitor Calibration and Gamma" and "Tonal
Quality and Dynamic Range in Digital Cameras".  It ties the analogue and
digital components together.  Some of it is heavy but it's worth persevering
- even if you have to take good breaks from it, try to go back as you'll
slowly see stuff fall into place.  Site's like Bruce Lindbloom's are full of
formulae and calculators which are useful from time to time but Normen's
site has more of the "why".  The only book I have found useful is Bruce
Fraser's Real World Color Management which is deliberately low on the maths.

> From: Tony Riley <listsubs@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Sun, 30 Oct 2005 15:59:58 -0000
> To: <digitalblackandwhitetheprint@yahoogroups.com>
> Subject: Re: [Digital BW] Black Density measurement
> 
> Thanks both to you and John Moody for setting me off on the right path.
> I have the Eye1 Pro and am using the Eye1 Share package to measure colour
> patches but it is inevitably a long learning curve from producing working
> profiles to understanding exactly what is going on "under the bonnet".
> 
> The reason for my request was that I am testing various papers to see which
> give the richest(most dense) black. I am quite surprised at the range and
> just how poor even some gloss papers are at good black reproduction.
> 
> Given that there is a fairly constant translation formula between L* and
> Density why is D considered preferable to L as a unit of definition?
> 
> Any good books out there that might make a good read in the bath? <grin>
> 
> TonyR
> 
>

> From: Tony Riley
>
> Can anyone tell me how to convert an L* measurement from an Eye1
> device to a D value?

If all you need is to do a few calculations, go here:

	http://www.brucelindbloom.com/

Click the Calc button, then the Companing Calculator link. Type a value into
the L* box, click the L* button, and the other values will be updated. The
Input and Output radio buttons aren't needed--they just control what's shown
on the graph.

--

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

Yikes!

Maybe I shouldn't have dropped that math class in college.

Gary

www.pbase.com/garyallenbrown






    Excel functions

    For Density to L
    =IF(Density<=2.05274,116*((10^(-1*Density))^(1/3))-16,116*(((903.3*10^(Densi
    ty*-1)+16)/116))-16)

    For L to density
    =IF(LAB_L>=8,LOG(((LAB_L+16)/116)^3)*-1,LOG(LAB_L/903.3)*-1)

--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Gary Brown" 
<baffin@c...> wrote:
>
> Yikes!
> 
> Maybe I shouldn't have dropped that math class in college.
> 


ColorshopX and read it directly from the density scratch pad, or even 
use Colorport and save as a non standard text file with densitometric 
measurements. If you use an Xrite device you could also use Toolcrib to 
get the same. I'm sure there are other applications out there to do the 
math for you, but as Steve pointed out, sometimes knowing what's going 
on can be useful.