Digital BW, The Print

Herb,

What you say makes sense only if there are a finite number of tones. In a
full range continuous tone silver print there are no steps between min and
max density but an infinite number of tones. If you can achieve a continuous
tone print from a digital source the same would apply there.

Which is why photographers have traditionally only looked at the range
between Dmin and Dmax as being of interest. The idea of a finite number of
tones is something that was born with digital imaging and has mistakenly
leaked across into analyzing continuous tone analog images.

Martin

----- Original Message -----
From: "hsitz" <hsitz@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, March 29, 2002 9:19 AM
Subject: [Digital BW] Is dynamic range more important than density range?


> I've been following (at least trying to follow) the lengthy
> discussion over dynamic range vs. density range.
>
> For my part, Austin has me convinced that proper meaning of 'dynamic
> range' of a print has to do with the number of steps available
> between its maximum density and a minimum density.  Still, it seems
> striking to me that the understanding of most non-experts mistakenly

(snip earlier)

> In a
> full range continuous tone silver print there are no steps between min and
> max density but an infinite number of tones.

There certainly aren't an infinite number of tones!

> Which is why photographers have traditionally only looked at the range
> between Dmin and Dmax as being of interest. The idea of a finite number of
> tones is something that was born with digital imaging and has mistakenly
> leaked across into analyzing continuous tone analog images.

Well I certainly disagree with that, it's by no means a mistake!  I've
always talked about dynamic range and number of tones in analog imaging.  It
really doesn't take an eagle eye to see that some prints can have more tones
than others!

Austin

Austin -- The mere fact that some prints have more tones than others 
doesn't have anything to do with the dynamic range of the medium 
(digital inks on paper) does it?   

Don't we have to distinguish between the dynamic range in the digital 
image itself (i.e., in its electronic form) and the dynamic range of 
the analog image that gets printed by a digital system?  For example, 
a black and white digital image may be composed of four different 
tones (in the computer) and when it's printed the image on the paper 
displays four different tones.  But that doesn't tell you anything 
about the dynamic range of the printing process (i.e., the 
combination of printer driver, digital printer, ink, and paper).  

For that you'd need to get an electronic image that itself had more 
tones than could be distinguished in the image of it that gets 
printed, AND you'd have to compare the two and see that the printed 
image doesn't have as many tones as were present in its electronic 
representation. Then you'd know that the paper/printing process had 
lower dynamic range than what was present in the electronic image.  

Isn't this related to the process of calibrating our printers with 
256 step wedges, making sure that each of the tones is 
distinguishable from the rest AND THUS maximizing the dynamic range 
of the printing system?  We can't tell whether the dynamic range of a 
printing system is low just because we see an image it printed that 
has low dynamic range (the source image might be the link with the 
low dynamic range).  But we can tell that a system has high dynamic 
range if we see an image printed by it that has subtle gradations in 
tone (dynamic range is at least as great as what's observed in the 
printed image).

Question:  assuming that we can calibrate digital printers to 
distinguish between the 256 shades of gray in a step image, how much 
more dynamic range is there in them?  We can use source images with 
up to 2^16 shades of gray in Photoshop (what is that, 65536 
shades?).  Can any of the print drivers make use of the extra bits?  
If so, then we could test just how much higher the dynamic range 
was.  

-- Herb
   



--- In DigitalBlackandWhiteThePrint@y..., "Austin Franklin" 
<darkroom@i...> wrote:
>I've
> always talked about dynamic range and number of tones in analog 
imaging.  It
> really doesn't take an eagle eye to see that some prints can have 
more tones

> than others!
> 
> Austin

--- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley" 
<mwesley250@e...> wrote:
> Herb,
> 
> What you say makes sense only if there are a finite number of 
tones. In a
> full range continuous tone silver print there are no steps between 
min and
> max density but an infinite number of tones. If you can achieve a 
continuous
> tone print from a digital source the same would apply there.


Martin -- Well, I'd say that what I say makes sense whether there are 
a finite number of tones or an infinite number that are available in 
a silver printing process.  But that if you think there are an 
infinite number of tones available to an analog process then you 
might just think it's silly to try to compare the 'dynamic range' 
(using Austin's meaning) of the two systems.  So you're left with 
comparing density ranges.  

By the way, I also think it doesn't make much sense to think of there 
being an infinite number of tones available in a silver process (even 
if there are in reality, which seems dubious to me).  Even assuming 
that there were an infinite subtlety of tones in some silver print, 
our eyes are a limiting factor there; there's no way we can 
distinguish adjacent tone steps from another after a certain subtlety 
of step size is reached.  If the dynamic range of digital printers 
increases to reach the ability to print tone steps more subtly than 
we can differentiate between them, then for all practical purposes 
the dynamic range of a digital print will be as great as that of a 
silver print.  

Our sensory perception has also shown up as a limiting factor in 
digitization of music, where even if the analog recordings had 
infinite gradations of tone, the (then more limited) subtlety of CD 
recordings captures gradations of tone beyond our ability to 
distinguish them.  (By the way, I think it turns out that audio CD's 
actually have greater dynamic range (i.e., more subtlety of tone)
than what you can get in an analog process, which kind of goes 
against there being an infinite subtlety of tone possible in silver 
prints.)

Similarly with digital projectors (you know, what businessmen use for 
presentations) and CRT projectors, which are analog.  A digital 
projector that has a resolution of 800 x 600 pixels will display an 
image that looks pixelated and digital if you look at it from a few 
feet away.  But if you move back to several times the width of the 
image you can no longer make out the pixel structure.  For all 
practical purposes, it will then appear seamless; we can no longer 
distinguish between adjacent pixels of the same color.  I know this 
example doesn't have to do with dynamic range of images, but it's 
related, I think.

-- Herb

> Austin -- The mere fact that some prints have more tones than others
> doesn't have anything to do with the dynamic range of the medium
> (digital inks on paper) does it?

It very well may, but it may also be just how it was printed...

> Don't we have to distinguish between the dynamic range in the digital
> image itself (i.e., in its electronic form) and the dynamic range of
> the analog image that gets printed by a digital system?

Not really, providing both are larger than the print medium.

> For example,
> a black and white digital image may be composed of four different
> tones (in the computer) and when it's printed the image on the paper
> displays four different tones.  But that doesn't tell you anything
> about the dynamic range of the printing process (i.e., the
> combination of printer driver, digital printer, ink, and paper).

That is very true, and that is why I have said you have to separate the
dynamic range of the image with the dynamic range of the system.

> For that you'd need to get an electronic image that itself had more
> tones than could be distinguished in the image of it that gets
> printed, AND you'd have to compare the two and see that the printed
> image doesn't have as many tones as were present in its electronic
> representation. Then you'd know that the paper/printing process had
> lower dynamic range than what was present in the electronic image.

Correct.

> Isn't this related to the process of calibrating our printers with
> 256 step wedges, making sure that each of the tones is
> distinguishable from the rest AND THUS maximizing the dynamic range
> of the printing system?

Yes.

> We can't tell whether the dynamic range of a
> printing system is low just because we see an image it printed that
> has low dynamic range (the source image might be the link with the
> low dynamic range).

But...if we print the same negative with two systems, and one has visibly
more tones than the other, then I believe we can say, in a general way, that
one has a higher dynamic range than the other.  The right thing to do to
really get to the bottom of this is get a test film that has 256 tones on
it, and see if both systems (wet and digital) can print it...  To avoid the
scanner issue, you could always do a 256 step wedge in PS, and send it
directly to the printer.

> But we can tell that a system has high dynamic
> range if we see an image printed by it that has subtle gradations in
> tone (dynamic range is at least as great as what's observed in the
> printed image).

Yes.

> Question:  assuming that we can calibrate digital printers to
> distinguish between the 256 shades of gray in a step image, how much
> more dynamic range is there in them?

You lost me, as I don't know what you're comparing it to.

> We can use source images with
> up to 2^16 shades of gray in Photoshop (what is that, 65536
> shades?).  Can any of the print drivers make use of the extra bits?

It has been said on the Piezo list that the PiezoPro/V6 uses 16 bit images,
and takes advantage of the additional bits...and people have said they
noticed improved tonality.  I have not seen that first hand...  I do have my
reservations on that claim though...given our eye limitations...

Regards,

Austin

----- Original Message -----

From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, March 29, 2002 11:09 AM
Subject: RE: [Digital BW] Is dynamic range more important than density
range?


> > In a
> > full range continuous tone silver print there are no steps between min
and
> > max density but an infinite number of tones.
>
> There certainly aren't an infinite number of tones!

If you print a continuous gradient on a piece of silver paper that begins at
paper white and ends at Dmax there are an infinite number of tones within
the range.

Continuous: 1 : marked by uninterrupted extension in space, time, or
sequence

Or, if you will consider, that the number of tones is so high that you eye
cannot distinguish between adjacent tones so as to simulate a continuous
tone. What would that mean in terms of your dynamic range equation?

> > Which is why photographers have traditionally only looked at the range
> > between Dmin and Dmax as being of interest. The idea of a finite number
of
> > tones is something that was born with digital imaging and has mistakenly
> > leaked across into analyzing continuous tone analog images.
>
> Well I certainly disagree with that, it's by no means a mistake!  I've
> always talked about dynamic range and number of tones in analog imaging.
It
> really doesn't take an eagle eye to see that some prints can have more
tones
> than others!

Somehow I knew you would. <G>

Is that because of the quality of the materials or how they were used?

Martin

Hiiiii Martin ;-)

> > > In a
> > > full range continuous tone silver print there are no steps between min
> and
> > > max density but an infinite number of tones.
> >
> > There certainly aren't an infinite number of tones!
>
> If you print a continuous gradient on a piece of silver paper
> that begins at
> paper white and ends at Dmax there are an infinite number of tones within
> the range.

Absolutely unquestionably incorrect.  You would need a piece of paper of
infinite size to print infinite tones, even if each tone is the size of one
atom.

> Or, if you will consider, that the number of tones is so high that you eye
> cannot distinguish between adjacent tones so as to simulate a continuous
> tone.

Well, that isn't hard to do since we already can do that with both inkjet
and chemical prints.

> What would that mean in terms of your dynamic range equation?

Your minimum discernable signal is now the limits of your eye.

> Somehow I knew you would. <G>

Some people knew about dynamic range long before digital cameras and digital
imaging became readily available to "regular" people ;-)

> Is that because of the quality of the materials or how they were used?

Could be either, and may be something else...and I believe that's image
dependant.

Regards,

Austin

----- Original Message -----

From: "hsitz" <hsitz@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, March 29, 2002 1:42 PM
Subject: Re: [Digital BW] Is dynamic range more important than density
range?


> --- In DigitalBlackandWhiteThePrint@y..., "Martin Wesley"
> <mwesley250@e...> wrote:
> > Herb,
> >
> > What you say makes sense only if there are a finite number of
> tones. In a
> > full range continuous tone silver print there are no steps between
> min and
> > max density but an infinite number of tones. If you can achieve a
> continuous
> > tone print from a digital source the same would apply there.
>
>
> Martin -- Well, I'd say that what I say makes sense whether there are
> a finite number of tones or an infinite number that are available in
> a silver printing process.  But that if you think there are an
> infinite number of tones available to an analog process then you
> might just think it's silly to try to compare the 'dynamic range'
> (using Austin's meaning) of the two systems.  So you're left with
> comparing density ranges.

Herb,

That pretty much sums it up form my point of view.
>
> By the way, I also think it doesn't make much sense to think of there
> being an infinite number of tones available in a silver process (even
> if there are in reality, which seems dubious to me).  Even assuming
> that there were an infinite subtlety of tones in some silver print,
> our eyes are a limiting factor there; there's no way we can
> distinguish adjacent tone steps from another after a certain subtlety
> of step size is reached.  If the dynamic range of digital printers
> increases to reach the ability to print tone steps more subtly than
> we can differentiate between them, then for all practical purposes
> the dynamic range of a digital print will be as great as that of a
> silver print.

If the printing medium, silver, digital inkjet or whatever, successfully
fools our eye into thinking it is continuous tone then does Austin's
definition of dynamic range apply, or if it applies, is it meaningful?  Can
we at least agree that our goal is to have a print that appears to be
continuous even though it may not be at some microscopic or quantum level?
>
> Our sensory perception has also shown up as a limiting factor in
> digitization of music, where even if the analog recordings had
> infinite gradations of tone, the (then more limited) subtlety of CD
> recordings captures gradations of tone beyond our ability to
> distinguish them.  (By the way, I think it turns out that audio CD's
> actually have greater dynamic range (i.e., more subtlety of tone)
> than what you can get in an analog process, which kind of goes
> against there being an infinite subtlety of tone possible in silver
> prints.)

I agree and was never able to hear the subtle distinction claimed by the pro
analog audio supporters. In theory it would have been nice to have sampled
at a higher rate but in practice no one could reliably tell the difference.
The new DVD audio standards seem to be excessive in the other direction.
Which leads to the point that once you have convinced the eye or ear that
they are receiving a continuous tone signal, how important is DR as Austin
defines it? Below that point its value is obvious but above it, as the noise
factor goes toward zero, it seems less and less meaningful in comparing
systems.
>
> Similarly with digital projectors (you know, what businessmen use for
> presentations) and CRT projectors, which are analog.  A digital
> projector that has a resolution of 800 x 600 pixels will display an
> image that looks pixelated and digital if you look at it from a few
> feet away.  But if you move back to several times the width of the
> image you can no longer make out the pixel structure.  For all
> practical purposes, it will then appear seamless; we can no longer
> distinguish between adjacent pixels of the same color.  I know this
> example doesn't have to do with dynamic range of images, but it's
> related, I think.

I think it is an appropriate example and illustrates that my claim of
infinite tones may be irrelevant once you have reached a number of tones
where the eye cannot distinguish between two adjacent tones.

Martin

> > Martin -- Well, I'd say that what I say makes sense whether there are
> > a finite number of tones or an infinite number that are available in
> > a silver printing process.  But that if you think there are an
> > infinite number of tones available to an analog process then you
> > might just think it's silly to try to compare the 'dynamic range'
> > (using Austin's meaning) of the two systems.  So you're left with
> > comparing density ranges.
>
> Herb,
>
> That pretty much sums it up form my point of view.

Then, how do you "describe" the difference in number of tones?  That is not
defined by density range.  All density range gives you is the lightest and
darkest tone...period  You could have an image that has ONLY the lightest
and darkest tone, and no intermediate tones...and then an image that has a
LOT of tones...both with the exact same density range.

> I agree and was never able to hear the subtle distinction claimed
> by the pro
> analog audio supporters.

It can take some audiophiles years to get "golden ears", as it take quite a
bit of experience to learn how to critically listen.  This is also true for
photography.

> I think it is an appropriate example and illustrates that my claim of
> infinite tones may be irrelevant once you have reached a number of tones
> where the eye cannot distinguish between two adjacent tones.

That depends on the print, now doesn't it?

Austin

----- Original Message -----

From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, March 29, 2002 6:54 PM
Subject: RE: [Digital BW] Is dynamic range more important than density
range?


(snip)

> > If you print a continuous gradient on a piece of silver paper
> > that begins at
> > paper white and ends at Dmax there are an infinite number of tones
within
> > the range.
>
> Absolutely unquestionably incorrect.  You would need a piece of paper of
> infinite size to print infinite tones, even if each tone is the size of
one
> atom.

Austin,

Remeber Plane Geometry? The Postulate that says that any line segment
contains an infinite number of points? A tone has no width so there is no
limit on how many you have within a line segment on a tone curve.
>
> > Or, if you will consider, that the number of tones is so high that you
eye
> > cannot distinguish between adjacent tones so as to simulate a continuous
> > tone.
>
> Well, that isn't hard to do since we already can do that with both inkjet
> and chemical prints.
>
> > What would that mean in terms of your dynamic range equation?
>
> Your minimum discernable signal is now the limits of your eye.

Then shouldn't were be looking at the limit of our eyes and not the prints?
And if the prints all exceed the discernable limit of our eyes wouldn't the
factor of interest then be the density range?
>
> Some people knew about dynamic range long before digital cameras and
digital
> imaging became readily available to "regular" people ;-)

Well the dictionary definition I gave you was from 1949, not pre-digital but
certainly based from radio broadcast days.
>
> > Is that because of the quality of the materials or how they were used?
>
> Could be either, and may be something else...and I believe that's image
> dependant.

As in negative or as in the actual scene?

Best,
Martin

----- Original Message -----

From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, March 29, 2002 8:00 PM
Subject: RE: [Digital BW] Is dynamic range more important than density
range?


>
> > > Martin -- Well, I'd say that what I say makes sense whether there are
> > > a finite number of tones or an infinite number that are available in
> > > a silver printing process.  But that if you think there are an
> > > infinite number of tones available to an analog process then you
> > > might just think it's silly to try to compare the 'dynamic range'
> > > (using Austin's meaning) of the two systems.  So you're left with
> > > comparing density ranges.
> >
> > Herb,
> >
> > That pretty much sums it up form my point of view.
>
> Then, how do you "describe" the difference in number of tones?  That is
not
> defined by density range.

If the mumber of tones is infinite or higher than we can differentiate then
the number of tones in not important.

> All density range gives you is the lightest and
> darkest tone...period  You could have an image that has ONLY the lightest
> and darkest tone, and no intermediate tones...and then an image that has a
> LOT of tones...both with the exact same density range.

 Well let's say it is a density range where the slope of the tone curve is
always less than zero which would be a requirement if the print is
continuous tone or simply mimicking continuous tone. Not even grade 5 paper
hits a zero slope and not may shot with litho film developed in litho
developer, not that I didn't try.
>
(snip)
>
> > I think it is an appropriate example and illustrates that my claim of
> > infinite tones may be irrelevant once you have reached a number of tones
> > where the eye cannot distinguish between two adjacent tones.
>
> That depends on the print, now doesn't it?

Okay limit the discussion to a print that contain a gradient then. If print
materials can produce a smooth gradient we generally find that they will
give as a good image print.

Martin

on 3/29/02 11:12 PM, Martin Wesley wrote:

>>> Or, if you will consider, that the number of tones is so high that you
>>> eye
>>> cannot distinguish between adjacent tones so as to simulate a continuous
>>> tone.
>> 
>> Well, that isn't hard to do since we already can do that with both inkjet
>> and chemical prints.
>> 
>>> What would that mean in terms of your dynamic range equation?
>> 
>> Your minimum discernable signal is now the limits of your eye.
> 
> Then shouldn't were be looking at the limit of our eyes and not the prints?
> And if the prints all exceed the discernable limit of our eyes wouldn't the
> factor of interest then be the density range?

Martin, isn't the point about noise this: you have to measure it (even if
that measure is a casual visual assessment) to know if it's relevant or not?

I hear and respect the logic of what you are saying IF the condition of
noise is so low as to be negligible, but in some instances that wont be the
case, and if you want to describe the state of negligible noise to a techie
you're going to need a measured value to present. Therefore, once you have
the measured value you might as well stick it into the DyR equation and see
what you get?

I mean I hear what you are saying, that sometimes it will be near enough to
zero that your DyR will be ABOUT the same as your DnR, but that doesn't make
that measure irrelevant, it simply allows one to decide whether it is
relevant or not.

Todd

> I mean I hear what you are saying, that sometimes it will be near
> enough to
> zero that your DyR will be ABOUT the same as your DnR, but that
> doesn't make
> that measure irrelevant, it simply allows one to decide whether it is
> relevant or not.

Whether noise is near 0 or not, density range and dynamic range are never
the same, simply because their units of measurement are entirely different.
Dynamic range is in dB, and density range is in density units.  They also
describe different properties.  Just because they both are stated in log,
doesn't make them the same.

A gallon of water isn't the same as an orange, though they are both stated
in integer units.

Austin

> > Then, how do you "describe" the difference in number of tones?  That is
> not
> > defined by density range.
>
> If the mumber of tones is infinite or higher than we can
> differentiate then
> the number of tones in not important.

You're avoiding the question.  Because they are not discernable to YOU does
not mean they are not discernable.  There are also prints that exist that
have a number of tones that we can differentiate.  How do you "describe" the
difference in number of tones?  NOT with density range...but how?

You've also shifted the discussion from your original claim, and are now
saying dynamic range isn't relevant because we can't see it.  The
interesting part is, you don't know that we can't see it, and you can't make
the claim that we can't see it in EVERY image printed, now can you?

;-)

Hi Martin...

> Remeber Plane Geometry? The Postulate that says that any line segment
> contains an infinite number of points? A tone has no width so there is no
> limit on how many you have within a line segment on a tone curve.

But measure those points on the line for me will you?  Get it?

> > > What would that mean in terms of your dynamic range equation?
> >
> > Your minimum discernable signal is now the limits of your eye.
>
> Then shouldn't were be looking at the limit of our eyes and not
> the prints?

But that's you putting the limit on this!

> And if the prints all exceed the discernable limit of our eyes
> wouldn't the
> factor of interest then be the density range?

Not necessarily.  How do you know you have a full set of tones?  Because you
may reach the limits of the eye in one "range", doesn't mean it does across
the entire print...hence posterizing ;-)

> > > Is that because of the quality of the materials or how they were used?
> >
> > Could be either, and may be something else...and I believe that's image
> > dependant.
>
> As in negative or as in the actual scene?

Not quite sure what you mean here...

Regards,

Austin