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

exposed. Density is only significant when the color quality of the exposing light is rigidly specified. References 1. James A. Larsen, "Improved Kodachrome sound quality with supersonic bias technique," Jour. SMPTE, 57: 60-62, July 1951. 2. John G. Frayne, "Electrical printing," Jour. SMPTE, 55: 590-604, Dec. 1950. 3. John G. Frayne and R. R. Scoville, "Analysis and measurement of distortion in variable-density recording," Jour. SMPE, 32: 648-673, June 1939. 4. J. O. Baker and D. H. Robinson, "Modulated high-frequency recording as a means of determining conditions for optimal processing," Jour. SMPE, 30: 3-17, Jan. 1938. 5. R. G. Lovick, "Densitometry of silver sulfide sound tracks," Jour. SMPTE, 59: 89-93, Aug. 1952. Discussion Anon: I'd like to ask the color temperature and the type of photocell used in the playback on all of your test curves? Mr. Lovick: The color temperature of the lamp used in the reproducer was 2800 K. It does make a difference. We use an unfiltered Type 868 phototube. Anon: It's a cesium cell? Mr. Lovick: It's a cesium surface with an S-l response. H. R. Kossman (Gamer aflex Corp.} : I would like to know a little more about the filter for the sound printer. Is it a glass filter you propose to use there? Mr. Lovick: No, we're proposing to use the Kodak Color Compensating Filters. They are gelatin filters. You have to cool these filters if they're tightly enclosed in some printers, particularly in contact printers. You don't have too much trouble in printers such as the Bell & Howell Model J. Mr. Kossman: You know, we have rather confined space there. Of course, they have a blower system. . . . Mr. Lovick: I realize that in many printers there is quite a confined space. However, you cannot get good sound reproduction unless you make some provision for using filters of this type to adjust the printer light to the color quality that will give you the best results. Mr. Kossman: I notice that some of the labs are using an ultraviolet filter. Mr. Lovick: The ultraviolet filter gives poorer results than you can expect from the color-compensating type of filter. It also takes considerably more light. F. P. Herrnfeld (Herrnfeld Engineering)'. You mentioned a 2-mm heat-absorbing glass. Which one do you use? Mr. Lovick: We use the Pittsburgh 2043. Mr. Herrnfeld: Have you investigated single-layer exposures? Mr. Lovick: Yes, single-layer and doublelayer exposures. It's necessary to use preflash techniques in order to avoid unmodulated silver sulfide density in the other layers. There's some improvement possible for variable-density records particularly in the exposure latitude. We don't lower the minimum distortion but gain in latitude by using a Wratten No. 29 filter to preflash the bottom layer. There's no particular value in trying to remove the middle layer of the film. You get improved latitude at the expense of the signal-to-noise ratio. George Lewin (Signal Corps Photographic Center) : Will you tell us how this new Kodachrome is going to be distinguished from the present type? Mr. Lovick: I believe the last of the old Kodachrome emulsion is 5265-953. The new films are number 1 or later. Mr. Lewin: It will not be necessary to order it specially? Mr. Lovick: No. Mr. Lewin: As time progresses, we'll start getting the new type? Mr. Lovick: The new type will be supplied as rapidly as possible. Mr. Herrnfeld: In your test, how do these filters compare with the emulsion pack you use for picture printing? Mr. Lovick: The filter pack for picture printing is a composite pack consisting of some cyan, magenta and yellow filters. I believe basically it's about 30 cyan, 30 magenta and 10 yellow. That's based again on the 2900 K source that's recommended for Kodachrome picture printing. Mr. Herrnfeld: Have tests been made using the picture printing filter pack to print the sound track? Robert C. Lovick: Sound Tracks on Kodachrome 87