International projectionist (Jan-Dec 1953)

VOL. 28 NO. 6 JUNE 1953 Wide-Screen Single-Film 3-D Predicted Appended hereto are excerpts from a paper presented recently before a distinguished scientific organization by John A. Norling, whose accomplishments in the stereoscopic motion picture field have won world-wide acclaim. Mr. Norling has contributed profusely to the technical literature on the art, including articles which appeared in IP during the past 20 years. This is the first integrated 3-D camera as developed by J. A. Norling, as contrasted with the double-unit cameras which were hastily assembled and pressed into service for the first 3-D pictures. The Norling camera is unique in that it is the only one that permits variable interaxial spacing of from IVz to 4 inches. A micrometer knob mounted between the lenses enables the cameraman to quickly adjust convergence. The single camera body compactly accommodates two film strips and handles as easily as a conventional camera, for extreme flexibility. //^^■HE FULL possibilities of 3-D have not been ex II plored," John A. Norling told 400 optometrists at ' the recent Central Atlantic Optometric Assembly in Atlantic City. "We look forward to wide-screen 3-D as an early embellishment of the art," predicted Mr. Norling, chairman of the Stereoscopic Motion Picture Committee of the SMPTE, "and to the eventual wedding of binaural sound with wide 3-D" Shown in full color, 3-D pictures carry naturalness to a point where the illusion is substantially complete and observers are likely to lose all sense of looking at pictures, said Mr. Norling, "provided the 3-D presentations do not contain depth distortions and exhibit other technical faults." Limits of Binocular Vision Any sensation of visual discomfort in viewing stereo movies is the penalty for exceeding certain geometric limitations imposed by Nature upon the use of our two eyes simultaneously, Mr. Norling explained. "Its cause is cumulative and lies in the breaking of one or more of a few exceedingly simple rules." The cine-stereo expert continued: "Complete visual comfort can be attained in stereo movies only if the two images are projected simultaneously, if they are rocksteady, if they are of equal brightness, if they are of equal contrast, if far distant points are not separated too far in one image from that of the other, and if they are of exactly the same size." Requirements for Good 3-D Mr. Norling discussed and demonstrated with stereo slides how 3-D films are made and projected so as not to exceed the tolerance of visual functions. In his opinion, good 3-D depends on: 1. Using lenses closely matched in focal length to limit differences in image sizes to one half of one % ; or one inch difference in height size between two superposed images on a 18 by 25 foot screen. 2. Vertical alignment: one image should not be higher or lower than the other. 3. Rotation : two images should be in accurate attitude alignment. 4. Illumination negatives should be matched in contrast and density. The depth effect disappears and visual discomfort ensues when one image is darker in projection. 5. Normal depth and appearance of objects and people. 6. The use of a "stereoscopic window" — that imaginary portal through which the projected picture is viewed — is another requirement of good 3-D presentations. To form the "window," 3-D cameras must have a means of INTERNATIONAL PROJECTIONIST • June 1953