International projectionist (Jan-Dec 1950)

Progress in Carbon Arc Lighting Appended are excerpts from an address given recently by W. W. Lozier, of the National Carbon Co., before the American Society of Cinematographers. While this address naturally focussed upon carbons for studio lighting, it has interesting implications for the theater field. IT WOULD perhaps be foolish to predict the course of future developments in carbon arc lighting. However, we can outline the direction of some of our experiments, our thinking and experience in other fields. Of course, just how much will be applied to any given field will depend upon the needs of that field, new developments, etc. During the past decade we have done a large amount of experimentation with water-cooling of carbons, particularly as applied to specially designed carbons. We have found with carbons of suitable composition and construction that water-cooling, properly applied, increases the ceiling on operating current and brightness. Arc Light Rivals the Sun For example, 13.6-mm diameter carbons can be operated at as high as 300 amperes giving a crater brightness of more than 1600 candlepower per square millimeter, which is equivalent to the apparent brightness of the sun. Other caibons have been operated at a brightness of over 2000 candlepower per square millimeter. Carbons presently used for studio lighting in general do not much exceed 900 candlepower per square millimeter brightness". The higher brightness of these newer carbons may find application where very intense beams must be projected. It has been demonstrated that "flame swallowers" can be used to control the positive tail flame and the products of combustion of the arc. A negative carbon in the form of a circular disc has been used abroad to obtain long burning life in small physical space. Air-blown arcs have been studied for special applications. Whereas these things may have been originally studied for application in other fields such as searchlights and motion picture projection, they are being scrutinized for studio applications. Phenomenal Amperage Levels Last year we carried out some experimental tests in Hollywood on 16-mm carbons burned at 500 amperes to produce at least twice as much light as the present maximum of the 225-ampere, 16-mm carbon used . in the Type 450 "Brute" spot lamp. Considerable numbers of searchlights were used in Europe during the war at very high currents, some of these ranging up to 1000 and 1200 amperes. Work was carried out here and also abroad on arcs at even higher currents for searchlights. These operated in some instances at currents as high as 4000 amperes. It is theoretically possible to generate all of the light needed for a large set with a few very powerful units. There would, of course, be problems of control and distribution of the light, getting it to the right places on the set. Perhaps we could turn back toward very early practices in motion pictures lighting where the light from the sun was used and directed into various parts oi the set by means of suitably placed reflectors. There would, however, be one important difference. The light source, instead of being the sun with all of its uncontrollable features caused by atmospheric and astronomical variables, would bo carbon arc lamps generating controllable and reproducible amounts of light of constant color. Summary of Arc Advantages Our laboratories are continuing their work with modern and improved equipment and are finding new and better ways of fabricating new and better carbons. . . . The result of these developments over Report Kodak Sets Jan. 1 Next For Nitrate Stock Exit Eastman Kodak Company is reliably reported to have set Jan. 1, 1951, as its goal for 100% conversion to acetate film by all film studios. The report emanated from a meeting of producer and technical representatives in New York at which was discussed the most feasible means for disposing of nitrate film prints as they outlive their usefulness. There is general agreement that even though acetate film will be used in production beginning next January, nitrate prints will continue to circulate for at least two years beyond that point before they are practically eliminated from the theater field. This means that projectionists will have to observe the same precautions as they do now with respect to identification and proper handling of both types of film. the past decade or so is that it has given us a well-rounded group • of lamps and coordinated carbons which produce highly successful results. It is perhaps well for us at this stage to stop and take stock, reviewing the attributes and advantages of carbon arc light. 1. Wide range of types and sizes of lamp units. These range from the 7500lumen output of light well diffused for broadside illumination from the Duarc lamp through the Type 90 and the Type 170 spotlamps on up to the Type 450 spotlamp with its maximum of a quarter million lumens output. 2. Very powerful units. The usage of powerful lamps such as the Type 450 "Brute" makes it possible to illuminate large sets with reasonable numbers of lamp units and obtain desirable modeling effects and directional control over the lighting. 3. The color of the light is best suited to the requirements of color photography. The color has a desirable daylight quality and there is no need for any mental compensation to allow for visual color distortion in order to anticipate the end photographic result. The essentially continuous radiation spectrum of carbon arcs very effectively furnishes all wavelengths important photographically. 4. The lamps have a fixed output. The light output and its color remain constant throughout the life of a trim and from one trim to another. Life, Cost, Dependability 5. Fixed life. At any given condition of operation carbon electrodes have a definite predictable life and you know just how long they will last. 6. Known costs. Due to definite bfe and other factors the operating cost can be reduced to definite tangible figures. 7. Carbon arcs are of proven dependability. There is no doubt about the light being available when it is wanted. 8. Immediate availability. The light from carbon arc lamps is instantly available without any need for warm-up, ovens, simmering current, etc. 9. Basic simplicity. A carbon arc source is fundamentally a very simple device. All that is required is that two electrodes connected to a proper source of electric power be touched, separated and then held a fixed distance apart. 10. Instant accessibility. Lamps can be examined and serviced immediately after shutting them off. There is never any need to defer examination of lamps until after they have been taken to a shop. 11. Carbon arc lamps are safe. Since they operate at normal atmospheric pressure, no undue precaution need be taken. Also, all voltages are in the range ordinarily accommodated without special provisions. 14 INTERNATIONAL PROJECTIONIST • MARCH 1950