Digital BW, The Print

As I teach both the Zone System and Digital printing now, I've been 
pondering this for a while...

>
>My initial questions/thoughts are:
>
>A – How can I carry out Zone system calibration digitally?  Or .

The traditional Zone System "tests" determine film speed (usually 
Zone I density .1D over film base plus fog to ensure printable shadow 
density) and developing time (to adjust film gamma to a given paper's 
ISO range at a specific highlight value, usually Zone VIII or IX). 
Neither are necessary for digital scanning/printing, but applying the 
principles can simplify workflow and adjustments.

For example, using a film speed that places Zone I at .1D above film 
base density allows setting the black point on the clear film and 
avoids clipping shadow detail.

Zone VIII highlight negative densities are usually between 1.0D and 
1.5D, depending on paper grade and type and enlarger (cold light 
needs more). That is a fraction of the density range capability of 
even flatbed scanners, of course.

While silver paper has a fixed ISO range, being able to select any 
white point in digital would seem to negate any need to adjust film 
gamma. Well, yes, in the same way auto focus eliminates the need to 
focus. The trade-offs include a loss of predictability, control, and 
subtle effects.

With many films, changes in development changes curve shape, 
graininess, and local tonal separation as well as overall contrast. 
These are all part of the "pre-visualization" which is the creative 
(as opposed to problem-solving) side of the Zone System. "Fixing it 
in Photoshop" is not unlike depending on dodging, burning, and 
split-filter printing to remedy poor exposure/development decisions. 
Why intentionally make image adjustment (darkroom or digital) more 
difficult?

One way to bring more predictability to the negative scanning process 
is to set the white point at a fixed value. You can do this by 
including a Kodak 96 2.0 neutral density filter in the scan, and 
setting the white value there rather than in the individual negative. 
A 2.0D range is roughly equivalent to the ISO range of a grade 00 
silver paper, so the image will look dark and flat . The 256 steps 
will then be mapped over a density range which will not stress the 
scanner, and you will have plenty of room to adjust the contrast by 
moving the 90% point up in PS curves (detail above 90% will be 
compressed much like a film shoulder when you do this).

Alternatively, scanning with an 21-step Stouffer wedge alongside the 
negative allows setting the white point in predictable increments, 
much like doing N+/- developing, or using contrast filters. This 
particularly fun with 16 bit raw scans.


>. .
>
>B - Should I carry out all negative and proofing procedures
>normally in the "wet" darkroom and then scan the resulting
>negatives for digital output?

Yes, if you envision making conventional prints for any reason. But 
if you only calibrate for digital, I'd concentrate on N and N- times 
and techniques. Expose for the shadows and develop for the highlights 
still applies. N+ times increase graininess and sacrifice shadow 
detail in a trade off for contrast.


>  Or . . .
>
>C - Do a classic "ring-a-round" for various lighting
>conditions
>and analyze the histograms for the best digital output?
>
>Option "C" sounds intriguing, has anybody tried this?  ALL
>opinions on these or other options are most welcome.

Edward Steichen was famous for this approach: 2000 exposures of a 
teacup and saucer, as I recall. In digital, if you set endpoints 
within the image, the software will try to eliminate differences. 
While this makes sense in the pre-press/transparency density range 
compression application the scanner software was designed for, it 
frustrates the control the Zone System was intended to provide.

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