306 THREE-DIMENSIONAL PHOTOGRAPHY
In developent, the ratio of time to density will depend upon
the composition of the developer and the temperature. Some de-
veloping agents have steeper progression curves than others. But
as a rule of thumb, use normal development when the meter
range lies within 1: 100, and try 1/2 to 2/3 development time when
the meter range is i:200 or more. Your own experiments will
soon indicate the correct factors. It is better to have the negative
too soft than too hard. You can use a high contrast paper, but if
the highlights are really blocked, you can do nothing short of
chemical reduction.
But nothing systematic can be done unless both extremes of
light intensity in the original scene are measured separately.
Most modern meters are good, but we have been using the G.E.
because it has a triple sensitivity range which is convenient for
deep shadows and because it fits the H8cH color meter attach-
ment, which has been discussed in the color chapter.
Control development is said to result in distorted tonal values.
Of course it does. How else can you reproduce an original range
of perhaps as much as i:800 upon a medium which at best will
give you i:80? You either “distort” the gradation and represent
every tone of the original in reduced form, or you obtain a print
in which most of the highlights are pure white, most of the shad-
ows are ink black and a small middle range is represented as a
succession of harshly stepped tones. It may be said that every
photograph made by sunlight either has such distorted tonal
values or it is worthless as a picture! The distortion, of course, is
but a matter of compression with some true but unnoticeable dis-
tortion of relative values in the extreme tones.
Developer.-Among the developers not commonly used by ama-
teurs, both pyro and glycin are excellent, but both require
experience. Old fashioned staining pyro is really superior to the
nonstaining types, but care must be used to avoid spots.
However, the mild alkali developers such as the borax types are
good: fine grain developers are also good, although the surface
types are not recommended. However, you will probably not care
to try processing unless you are familiar with ordinary planar
processing. You will, therefore, have some favorite developer, and
if it is one which gives you good printing negatives you can use it.
All stereo manuals emphasize the necessity for very soft nega-