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THREE-DIMENSIONAL MOTION PICTURES Four different cameras have been adapted for alter nate frame stereo motion picture photography. With this equipment a wide variety of applications have been possible. It should be noted that the mission of the Stereo Sub Unit, WAD€ Photographic Service Section, Wright-Patterson Air Force Base, is to accomp lish any type of stereo photography which it might be called upon to perform. Sixteen - millimeter cameras which have been adapted for alternate frame stereo photography are: Bell & Howell Filmo, the Eastman High Speed, an Eastman High Speed with Graham transmission, and a Cine Special. Each of the modified cameras listed now accomplish the requirement of exposing the right and left stereoscopic images on alternate full frames of the film. Cameras equipped with barrel type shutters lend themselves conveniently to alternate frame stereo adap tion, In such cases the barrel type polarizer principle can be in corporated as an integral part of the shutter. A split polaroid filter on the lens of the camera then provides for alternate selection of the right and left views on each 180 degrees rotation of the shutter. The axis of polarization of either half of the split filter on the lens is 45 degrees to the vertical and opposed by 90 degrees. Since the axis of polarization of the filter in the shutter is also on a 45 degree diagonal it acts, together with the split filter on the lens, to alternately eclipse either half of the latter during each half rev olution. Thus, when a beam splitter is centered in front of the lens, the displaced right and left views there from, entering their respective halves of the lens,. are recorded selectively on alternate frames of the film. This method of selection is particularly advantageous in high speed work where, otherwise, a mechanical shutter selector would be impractical.