232 THREE-DIMENSIONAL PHOTOGRAPHY
To result in stereoscopic perception then we must have par-
allax... this parallax must be multiple ,.. it must be differen-
tiated... it must be dynamic... then and only then do we have
that stereoscopic vision which because we always have had it, we
regard as a simple and unremarkable thing.
If you wish to know just how important this is, get a black patch
and tie it over your eye and leave it there for as brief a period as
a single hour. Then remove it. You will then begin to appreciate
the fact that stereoscopic vision is something far more important
in our lives than being merely the phenomenon which makes
stereo photography possible!
These principles will serve to make the explanation of space
control more easily understood.
SPACE CoNmoL.-Space control is a type of trick work which is
based wholly upon stereoscopic principles and has no counterpart
in planar photography. Incidentally, nothing equals it as a demon-
stration of the full realism of stereo and of the shortcomings of
planar photography.
Visual judgment of distance is based upon parallax. To repeat,
it is possible to list and describe a half dozen other factors which
are supposed to have some bearing upon it, but the fact remains
that the actual perception of distance is solely a matter of the
parallax involved. In fact, when the parallax is such that the
resulting size is unreal or even impossible, the visual perception
is unaltered and we actually see objects in impossible size rela-
tionships, regardless of all of the other so-called “distance factors”
combined.
Therefore, it is obvious that if an abnormal parallax can be
introduced, an abnormal distance will also be introduced. The
whole system of space control lies in this simple manipulation.
In the above figure, L and R represent the two camera lenses.
T is a table in the foreground and 0 is a living model twice as
far from the camera as the table.