PICTORIAL STEREOGRAPHY 137All of the so-called distortions of violent perspective are lost in
stereo, and the stereogram has a wholly normal appearance. Per-
haps there is no stronger evidence than this that the conventional
photograph is highly artificial, while the stereogram is wholly real-
istic and does actually reproduce direct vision to the last detail.
LIGHT AND SHADE.-If you look at a large white ball with the
light coming from directly behind you, the shape of the ball is not
definite. It may be a flattened or an elongated ball, but you cannot
be sure. If a planar photograph is made, the ball has the appear-
ance of a disc, but in a stereogram exactly the same vagueness of
form will be noted which is characteristic of the direct vision.
If the ball is lighted from above and at one side, the contour
shadows make its shape unmistakable to direct vision. To the
planar photograph these shadows impart a character which en-
ables the shape to be “read.” That is, we do not actually see it
standing out in relief, but we can see from the shadows that it
does have a round shape. The stereogram gives us the same defi-
nite perception that is seen in direct vision.
If a disc is skillfully painted with imitation contour shadows, it
does not readily fool direct vision, nor is the deception effective in
the stereogram. Both show it for what it is, while in the planar
photograph the painted disc and the true ball are hardly dis-
tinguishable, if at all. Thus it will be found that stereograms are
more decisively visible if a quartering light is used. This applies
to portraits and to landscapes, to large objects and to small.
Dramatic lightings may be freely used in stereo, because the
absence of the modeling light does not eliminate stereo relief.
But empty shadows should not be used, nor should light be used
as a positive element in the composition, for in the stereogram the
light will follow the contours of the surfaces upon which it falls,
and these will not have the same pictorial weight as in the planar
photograph. In a planar photograph a shadow or a highlight is in
essence a solid. In stereo a shadow is simply a shadow without
form other than the form imparted by the surface upon which it
falls, while light is simply light. These values are those of real
life which is considerably different from the “solid” values they
have in planar composition.
One exception to this is the definite beam, as from a spotlight
or a sunbeam from a window. If made visible by dust or smoke,