Digital BW, The Print

>Martin wrote-
>
>None of the modern films has a shoulder to speak of and density is linear to
>exposure.

I'm afraid this is incorrect. Characteristic curves for virtually all 
films are available on the manufacturers' web sites, and comparisons 
are informative. (I know this because I just went through this with a 
class, where we plot curves and compare to the "official" version). 
Tri X Pan, Agfa 400, and Delta 400 all demonstrate classic S shape 
curves. Fuji Neopan 400 is unique, with a pronounced 
shoulder-excellent shadow separation and blow out proof highlights. 
EK has just changed TMAX 100, and the new curve does show less 
shoulder. HP-5 and FP-4 are pretty linear. TMAX 400 has no 
straightline-it is all extended toe, with increasing contrast with 
increasing exposure. Fuji Acros 100 can look kind of similar. Tri-X 
Professional 120 is the worst in this regard, extremely "scooped 
out", with much higher highlight contrast than shadow contrast.

While the curves can be modified somewhat by different developers, 
the differences are real, and obvious on comparison prints (I have my 
4x5 students shoot TMY and HP-5 in the same filmholder). There are 
obvious implications for scanning, as toggling through all 
Silverfast's Nega Fix profiles on a single image quickly 
demonstrates. 8 bit scanning software clearly makes assumptions about 
a (given) film's tonal characteristics, but those assumptions are 
obviously not based on the photographer's actual preferred EI, 
developer, and time.

>However there are other limiting factors and experience tells me
>that the thinnest possible negative that retains all the desired detail
>yields the better print.

Certainly true for condenser enlarger printing of small format negs. 
Large format, not so clear.

>There is latitude but I think that this may still
>hold for digital as well and is a function of the chemical nature of film.
>The toe does remain though but I wonder if PS doesn't give us a way to
>straighten out a good portion of it.

Yes, the "screen"  blending mode works wonders.

>  >
>>  I think if you use film and a scanner there is another calibration step
>>  to the zone system - camera, film, developer and scanner.
>
>Exactly. Which also speaks to the benefits of doing and controlling your own
>scanning.

And another argument for scanning 16 bit.

>In all fairness though I have not had any problems scanning
>negatives that yielded good prints in the darkroom. So while additional
>optimization can be done, I don't think that we are too far off the mark.

The suggestion of cutting back development (N-1) makes sense, as does 
avoiding overdevelopment (especially with TMY and TXPro).

I always calibrated my Zone System times for grade 2 paper by contact 
or diffusion head enlarger. That produces a fairly robust negative, 
and vibrant prints. But as I get more involve with digital, I expect 
to re-calibrate to grade 3 in order to have slightly thinner, more 
scannable negatives.


-- 
Bruce C. Kinch
Associate Professor of Photography
The Art Institute of Boston at Lesley University