Digital BW, The Print

(snip)

> I think a silver print does have a DyR.  I'm not sure what noise
> would be in a silver print but I think the minimum perceptible change
> could be determined -- with some difficulty.  Perhaps it could be
> done by precisely exposing  and developing greyscale step wedges with
> veryfine increments in the grey.  If they were in say 1cm squares
> then the point at which you could no longer tell the difference
> between the measured densities of the squares would be the smallest
> discernable change.  No?

Kevin,

My reasons for believing this have to do with fact that crystal growth or
image stain are the result of chemical processes that can be very well
controlled in a stepless manner at least to the molecular level.

However, for the moment let's put aside my claim about infinite tones and
consider that the goal of a nice print would be to convince the eye that it
is truly continuous so that a subtle gradient in the image such as a sky
does not have discernable step changes in tone. Would you agree that is
generally our goal in printing?

If you cannot perceive the variation that Austin suggests might be the noise
of a print, then for practical purposes it is zero and the equation no
longer gives a meaningful result. Austin's equation would only seem to be
valid for systems that fail to produce prints that convince the eye that
they are continuous tone. You could use his definition to compare how close
they got to mimicking continuous tone. Once you have passed that point and
are comparing two systems that both convince the eye they are continuous
tone then his definition does not help you compare them in a meaningful way
and you are left with the old Dmax minus Dmin.

I also want to stress that the comparison of the dynamic range (whatever you
understand it to be) or the density range of systems is a technical
comparison and not an artistic one. Photography and especially digital
photography is so full of technical processes we tend to spend an inordinate
amount of time on them and often mix them in with considerations that are
purely artistic.

Martin