STEREO MOVIES 277PRACTICAL DETAILS8MM STEREo.-we have made 8mm stereo movies in the Guild
laboratory as well as 16mm and have found no significant differ-
ences. As the reflector may lie as much as an inch or so before the
lens, the field diameter rather than the lens aperture is the critical
dimension, so even the smallest lens openings operate satisfactorily
with the normal reflector.
OTHER METHoDs.-There are several other methods of making
stereo movies, but all of them demand more complex preparation.
First of all, there is the obvious method of using two cameras
and making two complementary films. This, then, requires two
projectors, but that is not the great objection.
Such a system demands exact synchronism in the projection,
and it demands double film expense. It demands the greatest care
in editing to keep both films identical, for even one frame mis-
match would cause trouble. Each film break means the same pains-
taking care. All in all it is simply too much trouble for amateur
use when the simple reflector method is available.
CONVERTED 8MM.-This is an excellent method, as it eliminates
the need for the compressor. But it requires some very accurate
camera conversion, and makes the camera unfit for planar use.
Any standard 8mm camera may be used as the basic equip-
ment. The aperture plate is removed and widened so that it is
full width (iomm) just as in a 16mm camera, BUT the height is
not changed, This provides the full size of an 8mm frame for
each of the stereo units, and when the reflector is used, the stereo
pair is recorded in normal format.
The camera will work after a fashion with no more alteration
than this, and it is simple. But for really good results it is neces-
sary to shift the lens center 2.5mm toward the film center so that
the lens is centered on the dividing line between the two images,
and this is difficult. The lens must retain its distance from the
film to maintain correct focus. The only practical solution is to
dismount the lens, make a new eccentric base to replace the old
one and substitute it. This requires the attention of an expert
instrument maker or camera repair man. The projector requires
a similar aperture plate conversion, but the lens shift is not as
critical as in the camera. Nevertheless, for a first class job, the