Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@y..., Todd Flashner <tflash@e...> wrote:
> Roy,
> 
> I'm sensing that some of us have locked horns when we are probably more in
> agreement than out of agreement. Perhaps if we all surrender a little ground
> we can turn this back into a useful discussion.
> 
> Is it possible that *some* people used the term dynamic range to describe
> something one step more complex than density range? I think behind Austin's
> absolutist rhetoric that is what he's saying.

Hi Todd,

I believe that other than Austin being an instance of "*some* people", no-one
uses the term like Austin.  Obviously,  I've have not polled everyone in the world.
But I really think if Austin is claiming "there are others" he ought to be able
to cite a couple.  Correct me if I'm wrong but I'm asked for a reference many
times so far and they don't seem to be forth coming.  On the other hand I've
cited some fairly noteworthy people that agree with my interpretation.  I
really don't think its a "I SAY" versus "HE SAYS" issue.  I'm just the messenger.
I think it is a IMAGING WORLD SAYS versus AUSTIN SAYS issue  -- and since
that may not to obvious I'm trying to show that.

Just to reclarify a little:  Dynamic range is the range of useful light values or
their representation in an Image.  Range is defined by a Maximum and a Minimum.
Describing  the range is the max and min, the size of the range would be the difference.
By "useful" (I liked Ansel's use of this word) I mean there may be light values
too dark or too bright to discern any information.  In photo language high values
that are blocked up or shadows that have no detail are NOT useful and
would not be included in the Dynamic Range.  Finally I say "light values" or
"their representation", what I mean is:  Imaging goes thru lots of steps, we
start out with actual light waves from a scene.  The range of useful light
intensities i.e. what you measure with your spot meter is the dynamic range
of the scene.  Here the dynamic range would be stops or EV (exposure values).
Once we put the image on film, the film itself doesn't have "light", it 
represents the information as densities.  Now the dynamic range is the
useful density range of the film.  Down in the film-base+fog doesn't count nor
does the blown out highlights (dense  part of negative).  Here we could
actually talk about the dynamic range of the type of film i.e. DyR of Tmax
for instance or we could talk about the DyR of a specific image on film.
When you get to the scanner, you've its DyR has be at least as large and
its min thru max has to completely cover the DyR of the image on film.
Again here DyR of the scanner is measured in density and its also
important to qualify with "useful" density range -- i.e. it has to discern
information within that Dynamic Range.   Most specs only quote the max
density because its assumed that everything from 0 to max is "useful".
So its a little more complex than just density range, but it never has the
flavor of "number of tones".   The staircase model seems so perfect
I'd like to keep pointing back to it.

> 
> Working with my sense of logic, which doesn't prove anything, let's look at
> the bigger picture. Lets consider a common situation we as photographers
> experience. Say through careful exposure and development we have a negative
> with a beautiful delicate distribution of tones throughout it's useful

This is a nice example, I'll throw some comments in as we go.

> range. It would perfectly fit all it's tones on a given grade 2 paper. Let's
> say that print's density range would be 2 units. If we could measure the
> print on a pixel by pixel basis it would yield a perfect distribution of
> tones in a histogram, right to the ends with no clipping. We could then
> print that negative on a grade 3 paper, which may also yield a density range
> of 2 units, but we "clip" tones from the image on both ends due to increased
> contrast. It's histogram shows the clipping accordingly. We could even
> extend the scenario to where we keep the print on grade 3 paper, but dodge
> the shadows and burn the highlights, thus maintaining a higher internal
> contrast through the midtones, without clipping the ends. It's density range
> is still 2 units, and it's histogram looks more like the grade 2 print, at
> least at the ends.

Great, the paper itself has a density range of 2 in each case.  Notice
however that how that range maps into the original scene is different.
Think about the dynamic range of the original scene that is now captured
on the two different prints.  In the grade 2 case, every tone in the original
scene (i.e. every tone in the original dynamic range) is represented in the
dynamic range of the final print.  Now in the grade 3 case, a section of the
darkest tones in the original all map into black on the print. Likewise a
section of the lightest tones all map into white.  So only part of the original
dynamic range of the scene shows up in the dynamic range of the picture.
Seeing how human beings are, they are more interested in images than
paper.  So when they say one print has more dynamic range they are really
thinking about how much of the dynamic range of the original image they
are seeing in the final print.

Makes me also wonder about doing a grade 1 print.  Here the DyR of 
original scene would be the same as in the grade 2.  But we wouldn't be
using the whole DyR of the paper, (no pure whites and no pure blacks)
and our "perception" would pick that up as the deficiency.  Interesting
how our brain would notice a deficiency either way.

> 
> Something *is* different in each of these prints, but it is not the density
> range. Is it possible that some people would say that the grade 2 print had
> a greater dynamic range than the straight grade 3 print, and that the
> manipulated grade 3 print might have had the greatest dynamic range of the

We're certainly getting in a nebulous area here.  Maybe what we are effectively
simulating more dynamic range in the original than was really there.  
Remember we are always manipulating the brain to produce a perception.
I guess the local contrast would be higher and the perception of
sharpness would also be enhanced.  Kind of like "unsharp masking" using the
real film method not the photoshop filter.

> three? If not dynamic range, what would be that term?
> 
> Todd
> 

Roy