[Leica] Sensitometry and gradation

[Mike Johnston <michaeljohnston@ameritech.net>]

> Comparing both concepts acutance or edge steepness (sharpness) and maximum
> range of grey values (tonality), is there anything that suggests that both
> are at odds with each other. Not at all!

> It is the fuzziness in the original statement that may produce confusion in
> sketching a dichotomy that does exist.


It is the fuzziness of your misreading of the original statement which is at
issue. Photographers pay lots of attention to sharpness and relatively
little to tonality. This is out of balance. That's all that was said. No one
ever suggested an "either/or" relationship between the two properties--that
is something you've supplied yourself, evidently to give yourself a windmill
to tilt at.

Second, you obviously know very little about tonality and tonal gradation in
black-and-white prints. Subject brightness range is interpreted as density
by the film and the the film density range is interpreted by the paper as
shades of gray in the end result. Different combinations of film, film
developer, and paper (FDP) produce different interpretations of the same
scene brightness ranges when the materials translate them as grays on the
paper: thus, with the same film and paper, one developer might tend to
render a middle value a little lighter relative to fixed endpoints, another
a little darker; another might expand highlight values and compress low
values, still another the opposite. The variations are as endless as the FDP
combinations themselves.

Tonality. Tonal properties of materials. The science is called sensitometry
and there is nothing in the slightest subjective about it.

It has nothing to do with your theoretical quasi-scientific maunderings
about the number of shades of gray between white and black. It has to do
with how different sets of photographic materials produce ranges of grays in
the print differently. Some quite markedly differently. Most every
practicing black-and-white photographer knows this happens, or has at least
recognized the practical effects in some vague way. Or were you under the
impression that all sets of materials translate similar subject brightness
ranges to the paper identically?

Go read Phil Davis's _Beyond The Zone System_ and then come back and give us
a book report. Davis invented a computer program that takes film/developer
data and paper data and plots the two together (it's much more complicated
and flexible than that, of course--you can set your own ES, select flare
value, development time, speed point, etc.). Adams's zone system is
hopelessly crude and scientifically inaccurate by comparison. Davis has
gathered densitometric data for hundreds of different film/film
developer/development time combinations and dozens of different papers. The
Plotter/Matcher plots the two against each other and the end result is a
graphic presentation of a specific FDP combination's gradation
characteristics helpfully plotted against a "standard" zone chart to help
users quickly and easily identify the gradation characteristics of any
specific set of materials they've chosen. Then, you can compare the
gradation characteristics of one FDP combination against another, match a
known one to a different combination, or in fact learn anything you want to
know, quickly and easily. You can learn more with this computer program and
data set in one evening than any photographer can learn about materials in a
year of hard work in the darkroom--even presuming first that that
photographer has a correct understanding of what he's looking for. Thus, the
program can demonstrate instantly how the gradation characteristics
(tonality) of, say, T-Max 100 in HC-110 printed on Kodak Polymax will
compare to, say, APX 25 developed in Rodinal and printed on MCC. Or any one
of a thousand other comparisons. The program is available commercially but
the data set that makes it so valuable is only available to students who
take BTZS workshops. Once you have the program you can also run your own
film and paper tests and enter your data in the database, provided you have
a densitometer and are willing to do the work. The database is infintely
expandable.

You might know something about optics but you don't know beans about
sensitometry, or about black-and-white materials and how they behave. At
least not yet.

- --Mike