Digital BW, The Print

----- Original Message -----
From: "Austin Franklin" <darkroom@...>
To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
Sent: Friday, March 29, 2002 11:06 AM
Subject: RE: [Digital BW] Dynamic Range Definitions and Print Tones


(snip)
> Yeah.  I don't know that you can quantify the dynamic range of a pizza.

It may have something to do with how fast I can grab a piece and how much
beer you got to go with it.

(snip)
> >
> > In photography the dynamic range has been takes as the density range
>
> Since when?  By people who don't understand what the real meaning of
dynamic
> range is, perhaps...

Since Ansel Adams and Minor White worked out the zone system and by
definition of the term dynamic range since the density difference gives you
the ratio of the minimum reflectance to the maximum reflectance.

From NASA website:

\ufffdThe dynamic range of an image is the ratio between the maximum and minimum
brightness levels in the image.\ufffd

http://nasatech.com/Briefs/Aug98/NPO20254.html



From the Cornell University Library:

\ufffdDYNAMIC RANGE is the range of tonal difference between the lightest light
and darkest dark of an image.\ufffd

http://www.library.cornell.edu/preservation/tutorial/intro/intro-05.html



From Digital Photography Review:

\ufffdDynamic range is the ratio between the brightest and darkest recordable
parts of an image or scene.\ufffd

http://www.dpreview.com/learn/Glossary/Digital_Imaging/Dynamic_Range_01.htm


(snip)>
> It depends on what you mean by "min" and "max".

See above.
>
(snip)
>
> It does not, except for using different multiplication factors for other
> reasons, but it is ALWAYS based on (largest signal divided by smallest
> discernable signal).  Always.

But the determination of what is the meaningful largest and smallest signals
is dependent on the system.
>
> > I understand that you don't agree with this
> > and see it as a universal concept. What I am saying here is let's
> > apply your
> > equation to a photographic print and see if the values help us
understand
> > what we see.
>
> Well, I have and it does ;-)

You have not been able to supply a value for the noise in your equation yet
so how did you manage that.
>
(snip)

> > > OK, then how does only using dMax and dMin give you anything dynamic?
> >
> > They tell you the size tonal space you can change tones in and
> > they tell you
> > the size of the largest change you can make.
>
> That is density range, not dynamic range.  Why on earth does the equation
> for dynamic range (the ONE AND ONLY one that anyone has presented, and
given
> a succinct reference for, namely the one I provided) clearly base dynamic
> range on smallest discernable signal?

Austin, that is simply not true. I have provided several of descriptions and
definitions of dynamic range from several sources. I have taken those an
written equations based upon the definitions. You simply say they are wrong
because they do not match your equation.
>
(snip)
>
> Yes, I know.  This is like trying to get Newtonian physicists to
understand
> Einsteinen physics...it goes against everything they based their beliefs
on.

Or Einsteinen physicists to under stand Newtonian physics. This is actually
and ongoing debate but that is another story. These things cut both ways.
>
(snip)
> > Okay, what would be a reasonable number of samples and which
> > tones should we
> > look at first?
>
> This is completely irrelevant to the overall discussion.  This is purely
an
> implementation issue.

Austin, I offer you a chance to look at what might be the noise value of a
print to use in your equation and you tell me that is irrelevant to the
overall discussion? If you cannot give this term a value than how can you
determine if your dynamic range tells you something significant about a
print?
>
(snip)
>
> >
> > Well since you have arrived at a possible concept for noise in a print,
> > design an experiment to determine a value. I have a Spectrocam
> > photospectrometer on order and I could try some readings across monotone
> > patches. I think that probably the variation may be much less that it
can
> > measure but it can't hurt to check.
>
> That sounds like a plan ;-)  What are the specs for the unit?

http://www.spectrostar.com/indexmsie.htm
>
(snip)
>
> > Now I am confused again. So what attribute of the print would you use to
> > determine min and max if not the whitest white and blackest black
>
> Good!  Confusion IS good...  Seriously.  OK, in the density range
equation,
> "max" IS simply the maximum density value you can measure by direct
> measurement, and "min" IS simply the minimum density value you can measure
> by direct measurement.  Simply put, measure the darkest patch, get your
max
> value, measure the paper, get your min value.

Austin, I have been saying that for post after post. What else could the
Dmin and Dmax of a print would be?
>
> For dynamic range, take dMax (from your density range measurement) and
> subtract your dMin (from your density range measurement), and that gives
you
> "max" for the dynamic range equation.  "min", basically, will be the
> variance across the patch that I've suggested above.

Okay, looks like the density range (or the log expression of ratio of the
reflectance) divided by the noise.
>
> > (snip)
> > > > Why do you say 3?
> > >
> > > X-Rite 810 manual ;-)
> >
> > Can you quote what they say or is it too lengthy? I'm curious because it
> > really is at odds with my own experience.
>
> Be happy to.
>
> Quoted from X-Rite 810 Operator's Manual, p. 51, section 6.0
> SPECIFICATIONS/6.1 Instrument Specifications
>
> REFLECTION SPECIFICATIONS
>
> Measuring Range: 0-2.5D
> Accuracy: +- .02D
> Repeatability: +- .01D
>
> TRANSMISSION SPECIFICATION
>
> Measuring Range: 0-4.0D
> Accuracy: +- .02D (0-3.50D)
>           +-   1% (3.1D-3.5D)
>           +-   3% (3.6D-4.0D)
> Repeatability: +- .01D
>
> Note, I was quoting the reflection specs, but note the transmission specs
> show it consistent across the entire range, up to the max of 2.5D.

Okay that is the X-Rite 810's uncertainly when it measures density but it is
much better at this than the human eye. Like many instruments it is only
linear over a specific range. This may be the case with our eyes as well but
believe me the human eye has a tough time discerning tonal differences above
2.4.
>
> > Doesn't that suggest that the ability for the eye to discern tones is a
> > function of the tonal density?
>
> Of course it is...but I don't see how that applies.

Just that it varies from light to dark so that you could not take a simple
seperation between discernable tones but would need to mathematically
account for this variation.
>
(snip)

> > What would the equation look like then?
>
> Don't know, I'd have to work it out...but as I've said, this is a red
> herring and completely irrelevant to the overall discussion.  It is merely
> an implementation detail.

If it can't be implemented what good is it? If you don't have the values you
need to apply your dynamic range equation, what use is it?
>
(snip)
> > > It depends on the print, of course!  Inkjet, using the Cone
> > system is over
> > > 100.  Silver I have not "counted", but I can easily tell when one
print
> > has
> > > "more" than another.  The same negative printed in a wet darkroom,
that
> > has
> > > a high dynamic range (many tones ;-) shows more tones on the
> > inkjet print
> > > than the wet print.
> >
> > How who is being vague? <G>
>
> Not me.  I am simply relating my direct experience.  It's not scientific,
> but it IS my experience.

And this had nothing to do with the operator but only the materials. <G>
>
(snip)
> > > Get a high range target and scan it ;-)
> >
> > What target do you use?
>
> Q-60...but also check with Edmund's or Stoffers.  Your sensitometer might
> come with one.  Some scanners do too...

Thanks,
Martin