International projectionist (Jan-Dec 1950)

capable of realization at this time. The result would be an increase of approximately 30% in available screen illumination with no increase in film difficulties or the demands made upon film. It appears from the work so far that condition C, an increase of approximately 60% could be obtained by efficient utilization of the information we have herein presented, and we have successfully obtained such an increase with no film diffir ulties in excess of those normally found under condition A. At this upper limit, however, the increase can be obtained with safety only through careful attention to the details of the cooling system. Some Limitations of System Throughout this discussion, little mention has been made of noise from air cooling, which is quite variable, depending upon the design of the nozzles, their location in the projector, the design of the projector itself, and even the source of compressed air. In our equipment, the air necessary for condition B can be applied with the noise of the air itself less than the normal operating noise of the projector. The air necessary for condition C in our equipment produces a noise level that is on the borderline approximately equaling the projector noise. If one attempts to use air in excess of this amount, however, the noise level increases rapidly and, as pointed out previously, the increase in cooling is slight. Additional drawbacks of this system are that a source of low-pressure air must be provided, that an additional control must be operated, that for optimum results in most cases a new projector design would be desirable (specifically planned to provide proper air nozzles, and so forth), and that at the higher ranges some safety provision must be incorporated to prevent damaging the film if the cooling air should fail during operation. Suggested Projector Changes We believe that the most practical application of these results will be in the provision of air cooling for new projectors designed for high-level application, and that in such design when room is provided for adequately streamlined nozzles, proper flow paths, and so forth, a result much superior to what we were able to obtain with existing equipment can be realized. In particular, such new design should make it possible to reduce still further the noise level encountered in our experiments and to reduce the required pressure and power of the compressed air. Inasmuch as the methods suggested by these experiments require consideration early in the design stages of projection equipment, the results are being reported now in order to make them available as early as possible to the designers of equipment — and for the assistance of those who must increase the performance characteristics of present equipment. Finally, it should be pointed out that the improvement obtained through the use of air cooling is not restrictive and that to these advances may also be added the previously outlined advantages of increased directional effect of the screen and the reduction of the heating from nonvisible components through the use of heat-absorbing glass, shutter modifications, dye images, and so forth. Conclusions (1) Present projection practice subjects film bearing a silver image to a radiant-energy flux near the maximum that film will stand without loss of image quality and film damage because of the high-intensity projection effects. (2) A substantial increase in screen illumination can be obtained if the film at the instant of projection is cooled and mechanically restricted by highvelocity air jets. (3) The increase in screen illumination so obtainable should be 30 to 60% beyond the present safe maximum. (4) Optimum use of air cooling during high-intensity projection requires the provision for such cooling in the design of the projector mechanism, and of the other components of a projection system. DISCUSSION: Dr. Norwood Simmons: In view of the fact that in process or background projection in Hollywood wherein the camera film is integrating the positive image on the process screen during its entire stay on the screen, what is the effect of this drift of emulsion position or change of best focus? Would you say that this is evident in background work as poor resolution or lack of maximum sharpness in the final print? Dr. F. J. Kolb, Jr.: It has always seemed to us that this negative drift we described must result in a lack of sharpness in background projection. The camera has no psychological mechanism such as the eye does, and the camera sees the image in all of the stages of drift from near-flat to maximum negative. Most of the time, the camera sees an out-of-focus image. Unfortunately, our experience with background projection in Rochester is quite limited, and we have no photographic verification of the lack of sharpness in a negative exposed to a process screen. We should certainly be surprised, however, if it were not an important factor in the quality of background projection. Mr. David B. Joy: I believe this is probably one of the most important papers from the standpoint of projection that we have heard here for a good many years, because all of us who are connected with light and its projection on the screen have realized that we have come up against an upper limit with the necessity of having to use some kind of a heat filter which at the same time absorbs an appreciable amount of light. With the way pointed by this paper, that upper limit has been raised, and it would look as though it should be a great stimulus to the theaters in getting more and better light on a screen. I assume that this method is open to anybody who wants to make a practical application of it. Is it, Dr. Kolb? Dr. Kolb: We should be pleased to cooperate with anybody who is interested in making use of air cooling. EXPORTS OF MOTION PICTURE VISUAL AND SOUND REPRODUCING EQUIPMENT 1949 1948 Equipment Units Dollars Units Dollars 35-ann Projectors 2,424 837,579 4,154 1,637,67? 16-mm Silent Projectors 4,046 382,602 4,830 543,753 16-mm Sound Projectors 9,017 2,245,499 8,440 2,357,505 8-mm Projectors 5.887 363.884 9,278 636.362 Total — -21,374 3,829,544 26,702 5,175,299 Sound Recording Equipment — 615,674 — 1,591,696 Sound Reproducing Equipment — 1,474,259 — 1,882,988 Arc Lamps 1,151 267,003 1,887 419,233 Motion Picture Screens — 264.890 — 347.323 Total 2,621,826 4,241,240 Total Equipment: 7,621,485 10,972,516 INTERNATIONAL PROJECTIONIST • MARCH 1950 11