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

1949 TELEVISION FORUM DISCUSSION 127 Mr. Moderator, I should like to ask Mr. Blount if the visual luminosity curve he showed was based on equal energies or on tungsten at 3000 degrees Kelvin. MR. RICHARD BLOUNT: Equal energies. DR. SIMMONS: Is it not then true that the visual-luminosity curve, in order to be fairly compared with the product curve of the tube sensitivity multiplied by the light-source-output curve, should also be multiplied by the relative output curve for the particular light source being considered? MR. BLOUNT: In both cases, to be highly accurate we should have used fluorescent lamp or the 3000. I do not feel that for the basis of this presentation that degree of accuracy is warranted. MODERATOR HYNDMAN: Dr. Simmons, do you not think that there has been confusion here this afternoon, with some in the television industry and some in the motion picture industry continually talking about controlling contrasts by controlling gamma, when we think of gamma as applying to a development factor only? Literally the problem is, in the majority of motion picture films produced, there is a brightness latitude greater than the television system or chain is capable of accommodating. For illustration, a latitude brightness range of 1 to 40 in a motion picture film may be common, and the television system has about 1 to 20, then television-image distortion of tone occurs regardless of gamma or density. DR. SIMMONS: I quite agree with you. I was extremely interested in Mr. Bertram's samples and should like to congratulate him on an excellent set of tests and to tell him that had we had such a set of tests in Hollywood at any time in the last six months, it would have straightened out a great many people. I am thinking of the nontechnical people involved in making these films for television, and we have tried to straighten them out without the aid of such tests. This was a very illuminating test to me. I think it is important, though, to point out that, at least as I saw it, the 1.705302 print appeared less "contrasty" on the screen than the 1.25 fine-grain master positive which is because we are dealing with toe portions of the characteristic curve. If we consider that the fine-grain master positive has a steeper and shorter toe than regular release positive film, then, in consequence, the true contrast of the screen image is not in proportion to the gamma values as read. Therefore, it behooves us to consider the curve shape. I may be deviating somewhat from your question, but I did want to mention that in Hollywood the National Broadcasting Company and others have given thought to that matter of curve shape. That is cutting it rather fine possibly, but since there is less toe on the fine-grain film, therefore, we have more high-light contrast relative to middle tone and high-density contrast. Some people think that helps. Personally, I do not think the art or science of television has advanced far enough to allow us to see any difference yet, and I agree with you, Mr. Hyndman, in saying that at the present time the contrast of the print provided is of secondary importance. MR. EDMUND A. BERTRAM: To answer Dr. Simmons' question or agreeing with him, it is too bad I do not have time to make a slide of the curve characteristics, but I do have all the characteristic curves of the particular films shown in the 35-mm form. The print at gamma 1.70 is made on a high-contrast film, and printed on 5302, developed in negative developer in which we tried to develop a shadow density well up on the curve to produce transparencies in the black and at the same time bring up the toe.