222 THREE-DIMENSIONAL PHOTOGRAPHY
is that which involves two uncontrolled subjects. For example
you may make an exposure of a model seated in a chair. The pose
must be comfortable so that it can be held for several seconds
while preparing for the second exposure. It is essential that the
camera be mounted upon a rigid tripod.
After the first exposure, which should be less than normal but
not less than 1/2 normal, a second model is introduced, and
a second exposure made. The sum of the two exposures should
approximate the full normal exposure.
The first shot records the first model and the background and
the second exposure repeats this. However the second exposure
has the second model in place. The background behind the sec-
ond model will receive a short exposure as will the second model.
The result is one which shows the second model as a ghostly
figure through which the background is seen. The background is
darkened just enough to suggest the semi-solidity of the second
figure.
This is an old trick in ordinary photography, but it does not
prove very effective in planar work because the second figure ap-
pears to be painted upon the background. In stereo the ghostly
figure stands out in space with the background behind her. This
gives the complete illusion of a fully transparent figure standing
out in space. A true ghost. This is not difficult and provides
possibility for many amusing shots.
It might be added that the sum of the two exposures may equal
1% times normal with no ill effects.
MASKED DOUBLE ExPosuRE.-This is a somewhat more ambi-
tious version of the double exposure. The simplest “mask” con-
sists of arranging some part of the background so that it will be
in deep shadow. The exposure is made, for example, with a male
model who is smoking. A cloud of smoke before the deep shadow
provides an efficient setting for the second shot. This shot may
be made freehand, but it is essential that the position of the
deep shadow be remembered with some accuracy.
The second model is now posed against a dark background, and
the second exposure made. The figure of the model is placed in
the position occupied by the deep shadow, and the finished result
will show the second model in line with the cloud of smoke.
The worst difficulty in this type of work is that the dark back-