THE CONCEPT OF VARIABILITY

Photographers are by necessity experimenters.
Although they are not thought of as scientists
operating in a research atmosphere,
they most certainly are experimenters: Every
time an exposure is made, and the negative is
processed, a genuine experiment has been
made. There is no way the photographer can
precisely predict the outcome of such an experiment
in advance of doing the work. The
objectives of the experiment derive from the
purpose of the assignment, and the procedures
flow from the photographer’s technical
abilities. The success of the experiment will
be determined by evaluating the results. Finally,
conclusions are reached after interpreting
the results, which in turn shape the
performance for the next assignment/experiment.
It is the last step in the sequence,
namely, the interpretation of test results and
the conclusions reached, that we will be concerned
with in this section.
A great deal of what is written about the
practice of photography consists of opinions.
When someone states that “black-and-white
photographs are more artistic than color photographs”
or that “condenser enlargers are
better than diffusion enlargers,” it represents
an expression of personal judgment. Such
statements are properly referred to as subjective
because they arise from personal attitudes.
Because opinions are statements of
personal feelings, they are neither right nor
wrong and, consequently, are always valid.
The problem with subjective opinions is
that they lead to conclusions that are not
easily tested and analyzed. Therefore, when
one relies solely on personal opinion, the
possibilities for obtaining new insights into
the photographic process become very
limited.
Because of the potential ambiguity of subjective
opinions, it is often preferable to use
numerical expressions that have been derived
from measurements. Such numbers
can be considered objective in that they are
generated outside of personal attitudes and
opinions. For example, the blackness of a
photographic image can be measured with a
densitometer and the result stated as a density
value. Such a numerical expression of
its appearance can be obtained by independent
workers and therefore verified. Although
there may be many subjective opinions
about the blackness of the image, there
can be only one objective statement based on
the measurements. Consequently, a goal of
anyone who is experimenting is to test opinions
with facts that usually are derived from
measurements.
Whenever an experiment is performed and
a result obtained, there is a great temptation
to form a conclusion. For example, a sample
roll of a new brand of film is tested and
found to give unacceptable results; most
photographers would not bother to purchase
another roll. On the other hand, if the temperature
of a processing bath was found to be
68° in the bottom of the tank, many people
would act as if it was the same everywhere.
Such conclusions should be resisted because
of a fundamental fact of nature: No two
things or events are ever exactly alike. No
two persons (not even so-called identical
twins) are exactly alike and no two snowflakes
are ever identical. Photographically
speaking, no two rolls of the same brand of
film are exactly alike. No two frames on the
same roll, no two areas within the same
frame and indeed no two silver halide crystals
are ever truly identical. If the inspection
is close enough, differences will always be
found. Stated more directly, variability always
exists.
In addition to these differences, time creates
variations in the properties of an object.
The photographic speed of a roll of film is
not now what it was yesterday, nor will it be
the same in a few months. Using this point of
view, an object, say a roll of film, is really a
set of events that are unique and will never be
duplicated. As the Greek philosopher Heraclitus
long ago said, “You cannot step in the
same river twice.”
With this view of the real world, it should
be obvious that an essential task of the photographer/
experimenter is to determine the
amount of variability affecting the materials
and processes being used. This will require
that at least two separate measurements be
made before reaching a conclusion about the
characteristics of an object or process. A photographer
who ignores variability will form
erroneous conclusions about photographic
materials and processes, and will likely be
plagued by inconsistent results.