Journal of the Society of Motion Picture and Television Engineers (1950-1954)

J. M. Calhoun, "The physical properties and dimensional behavior of motion picture film," Jour. SMPE, 43: 227-267, Oct. 1944. C. R. Fordyce, "Improved safety motion picture film support," Jour. SMPE, 51: 331-350, Oct. 1948. scussion S. J. Begun (Clevite-Brush Development Co.) : tfore I ask my question, I would like to press to Mr. Dedell my appreciation for very excellent presentation on this par;ular subject matter. Now, to my quesm. You mentioned, I believe, that you uld store dispersions for approximately I days. I wonder whether any particular mditions during storage have to be mainined as far as temperature is concerned, id whether any other precautions have to 5 observed? Mr. Dedell: We ordinarily store the dis;rsion in 8-oz bottles. We usually make b dispersion in gallon mills and pour it 3m the gallon mill into 8-oz bottles; you ;t something like five 8-oz bottles of dis>rsion. These are kept tight and are set i a shelf for as long as 30 days, and we ;e them up to that length of time. Just ifore we use them we tumble them for 3out 30 minutes. Outside of that there •e no special conditions for keeping, hey do not have to be agitated the whole ) days, or anything like that. j Mr. Begun: Might I ask another queson then? I am wondering whether you el that this method of applying a magnetic riping to film could be brought to a point here the individual processor, or maybe )ie smaller camera shop, might be able to pply it? | Mr. Dedell: I think the answer to that is lie cost of the machine. The coating lechanism is a precision instrument. You lave to have the idler roll and the appliator roll within about a ten-thousandth f an inch of being a perfect circle, and lat adds quite a bit to the cost of the achine and the maintaining of it. Anyne can make the coatings if they can Eford the machine, and anyone here ith about 10 minutes' instruction could lake coatings on it. E.W. D'Arcy (De Vry Corp.} : What factor f control do you have over the recording naracteristics of your striping? Mr. Dedell: Only in following the direc tions which I have just given for making up the dispersion formula. That is, you have to weigh out the quantities accurately, the viscosity must be controlled correctly, and distance between the applicator roll and the film must be accurately set. With proper attention to these points, you will then end up with tracks of uniform quality. George Lewin (Signal Corps Photographic Center) : I might have missed this point in your presentation, but did you indicate whether or not this coating can be applied on the inside half of the track, or does it have to be on the outer edge of the film? Mr. Dedell: I didn't mention that. The coating can be made in widths up to 100 mils, any width you like, and it can be positioned any place you want to put it. Mr. Lewin: Also, you gave some figures on percentage of amplitude modulation. Could you tell us a little bit more as to how you measure it? What I'm getting at particularly is what rates of amplitude variations are included in your figures? The percentage figures seem rather low. J. R. Horak (Kodak Research Laboratories) : These amplitude modulation figures were taken at 3000 cycles at 1\ in. per second, and they are average readings. They are not peak readings at all; they're average fluctuations. Mr. Lewin: In other words, they don't show very rapid fluctuations, do they? Mr. Horak: No, only up to 500 cycles. Mr. Lewin: They do show up to 500 cycles, however, do they not? Mr. Horak: Yes, we have a 500-cycle low-pass filter following the detector. Mr. Lewin: That just doesn't seem to jibe with graphs that I've seen. Mr. Horak: Well, we have a rather high pressure on the pressure roller holding the tape to the record head and that may account for the difference. Mr. Lewin: Were these figures taken on the new Eastman projector? Mr. Horak: No, this is a special machine we have built in our own laboratory just 4or making tests on £-in. tape. It has very high pressure on the record head and also pretty high tension on the loop drive. Mr. Lewin: In other words, it doesn't represent what you'd realize on commercial projectors. Mr. Horak: We are trying to find out exactly what the tape is capable of. There Thomas R. Dedell: Magnetic Tracks for Processed 16mm Film 499