Journal of the Society of Motion Picture Engineers (1930-1949)

Letters to the Editor Re: Three-Dimensional Motion Picture Nomenclature I have read with great interest Major Bernier's article on "Three-Dimensional Applications" which appeared in the Jour. SMPTE, 56: 599-612, June 1951. Major Bernier is to be congratulated on his paper and also on the interesting experimental work which he and his unit are conducting. The writer would, nevertheless, like to draw attention to a few points in the paper in connection with which there seems to be some confusion. On page 599 in the Journal, reference is made to "the composite or lenticulated system," but just what Major Bernier is endeavoring to convey by this terminology is not clear. There are three main groups of processes (embracing hundreds of different modes of application) which might conceivably, but should not, be referred to in this way. These three groups comprise: (1) integral processes, which had their genesis in the idea conceived by Gabriel Lippman and disclosed by him in 1908 (Compt. rend., 746: 446-51); (2) parallax stereogram processes, all of which are derived from the principle described in Frederic Ive's U.S. Pat. 725,567 (application date, Sept. 25, 1902); and (3) parallax panoramagram processes, which depend on the principle of G. W. Kanolt, described by him in his U.S. Pat. 1,260,682 (application date, Jan. 16, 1915). The problems involved in producing spherically lenticulated film as proposed by Lippman were not solved during the inventor's lifetime, but the earliest practical process (for still photography) employing a cylindrically lenticulated screen with which the writer is acquainted was described by Walter Hess in 1911 in his Brit. Pat. 13,034. The most important of Dr. Herbert Ive's ideas relating to stereo kinematography are those embodied in Brit. Pat. 348,118 (application date, Feb. 7, 1930) and his corresponding U.S. application (convention date, Feb. 9, 1929). Very many other processes involving the use of line or lenticular grids, for both still and motion pictures, were evolved between 1911 and 1929. In discussing, on page 601 of the Journal, the various factors contributing to depth I perception, Major Bernier has again departed from accepted terminology, and this may be confusing to some with limited knowledge of the subject. For example, factor No. 4, in Major Bernier's list should read "Accommodation," not "Focus reaction," and factor No. 6 should read "Binocular vision," not "Stereoscopic vision." The word "stereoscopic" means (freely translated from the Greek), of course, "seeing solid" or, as we are accustomed to say, three-dimensionally or stereoscopically. Accordingly, the term "stereoscopic vision" applies to the net effect resulting from the various contributory factors. In compiling a "short list" of these factors, it is, in the writer's opinion, difficult to improve on the custom of dividing them into two groups: (1) monocular factors; and (2) binocular factors. In the first group the chief factors are accommodation and perspective, and in the second group we have parallax and the faculty of convergence. There are numerous subsidiary factors, some of which are mentioned by Major Bernier. Referring to the comments in the second paragraph of page 601, whilst it is, of course, true that accommodation becomes of decreasing importance with increasing distance of the object, neither this fact nor any other warrants definition of a distance of 20 ft as "optical infinity." The reasoning on the next paragraph of the paper is based on a fallacy. It can best be demonstrated experimentally that the faculty of accommodation is stimulated practically always when one is watching projected motion pictures. The apparent size of the image is no less important than the distance of the screen in determining the degree of stimulation. Let us suppose, for example, that the film being projected depicts an object moving toward or away from the observer so that it is progressively either increasing or decreasing in size. If the object depicted is a familiar one, and the apparent size of the image corre 70