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

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Discussion for This Reprinting By Pierre Mertz The paper by Messrs. Collins and Macnamara describes a proposal that will be followed with great interest, for the application of television to motion picture production techniques. The objective "that, to be acceptable, motion pictures made by the process described in the paper must to all practical intents and purposes be indistinguishable from those made by ordinary optical methods" will appear especially challenging. A point which the authors undoubtedly have in mind, but do not emphasize, is that in large measure the television processing which they are proposing is to be inserted in tandem with the photographic and optical techniques at present existing. Thus to set detailed objectives on quality it is necessary to investigate not merely the performance of the latter processes, but also the additional impairment expected from the insertion of the television processing. In such a case, in general, the inserted impairments need to be not simply of the same order of magnitude as those already existing (in the optical and photographic processes) but one or two orders of magnitude lower. The authors are diffident about the tentativeness and controversial nature of their data and conclusions on photographic and television performance. Because of this it would seem helpful in a number of places if they could give documentation for the data they introduce. In particular, the authors have not referred to the extensive work At the request of the Chairman of the Society's Board of Editors, at the time of reviewing this paper, this discussion was prepared by Pierre Mertz, Bell Telephone Laboratories, Inc., 463 West St., New York 14, N.Y. of Otto Schade1 on many questions which apply closely to their problem Other specific points upon which documentation would be helpful are: (a) The film density ranges mentioned by the authors seem modest compared to the projection density measurements reported by Tuttle2 in 1936. Tuttle's minimum densities run a bit higher than the authors': at low, 0.18; median, 0.41; and high, 1.05. His maximum densities, however, run substantially higher: namely, low, 1.90; median, 2.21; and high, 2.65. The influence of stray light in the theater on the projection contrast was discussed in a symposium of the SMPTE in May 1951.3 S. K. Guth, in particular,4 mentions a maximum desirable level giving 0.07 ft-L on the screen (which has a clear screen brightness of 5 ft-L). This leads to an equivalent density of 1.85, which still is over the authors' allowance of 1.7. (b) The authors' figures on motion picture definition correspond generally with those found by an SMPTE committee in 1946 and referred to by Schlafly5 in 1951. It would be interesting, however, to have more specific information on the "good-quality 35mm lenses of today . . . capable at full aperture of resolving from 8 to 10 times the fineness of detail normally required for making a film optically." (c) The explanation which the authors give of "dynamic resolution" is the conventional one. However, in any casual experience which I have had, the increase over the "static resolution'* was not realized, possibly due to "jump" and "weave" of the picture. It would be interesting to have any documentation on actual experiments which the authors might know of. (d) Again on the subject of definition, 458 December 1952 Journal of the SMPTE Vol. 59