STEREO MOVIES 275be added that this does not interfere at all with non-stereo use of
the camera.
COMMERCIAL REFLEc-roRs.-Please note that the stereo reflector
is NOT a beam splitter, a term which has come into use. It does NOT
divide a single beam, so the correct term is “Reflector” or “Prism.”
The Berthiot and Bolex reflectors are complete optical systems
which replace one of the lenses of the motion picture camera.
They seem to be based upon the conventional reflector design.
The Nord attachment uses prismatic deviation rather than reflec-
tion to keep the fields separate.
We have not had the opportunity to test any of these devices
so it is impossible to give a report of performance based upon per-
sonal knowledge. However if correctly designed and accurately
built they should be perfectly satisfactory, and we hope we shall
have an opportunity to try them before our next edition.
Note that there is no polarization involved in the camera work.
Once the accessories are correctly adjusted and the diaphragm
set for the exposure ‘factor, the rest of the procedure is that of
normal movie making. Objects within 30 feet of the camera, or
so, will provide better results. The film is processed as usual.
PRojEcTIoN.-The two images of the film must be projected in
superposition, just as in regular stereo projection. When a fixed
reflector is used, something is necessary to provide adjustable su-
perimposition. This may be a pair of mirrors at slight angle, or a
series of weak prisms which are placed over the lens base to base.
However, the serious amateur will have an adjustable reflector
made and when this is done, the same reflector used on the camera
will be used with the projector and the mirrors adjusted to pro-
vide the superposition. This is by all odds the best method.
The whole accessory unit of compressor-reflector is removed
from the camera and supported before the projector. In front of
the reflector openings are placed the two Polaroid filters with
their axes at 45 degrees left and right so the standard 3-D viewing
goggles may be used.
When superposition is obtained, no further adjustments are
necessary and projection proceeds in a normal manner.
Filter position is easy to check. If the axes are reversed, dis-
tances will appear in reverse. When correct, relief will be nor-
mal. If a filter is “between” extinction positions, two images will