Motion Picture Herald (Jul-Aug 1943)

70 BETTER THEATRES August 21, 1943 On Guadalcanal . . . On Elm Street B&L Microscopes, and the advances in microscopy that optical developments by Bausch & Lomb have made possible, are serving America well today. Bausch & Lomb Microscopes are helping to keep America's righting forces healthy on all the world fronts. Medical research . . . and the routine checkups and analyses that must be done in the field . . . are a vital part of military preventive medicine. On the home front, too, microscopes are performing vital war duty. In doctor's offices, in research laboratories and in the industrial research, inspection and control that speed production of the tools of Victory, microscopes are in constant daily use. Here is another instance where optical skills, experience and facilities acquired in the years of peace are helping to see us through a critical period. For Bausch & Lomb Instruments essential to Victory — priorities govern delivery schedules. BAUSCH & LOMB OPTICAL CO. . ROCHESTER, NEW YORK ESTABLISHED 1 853 AN AMERICAN SCIENTIFIC INSTITUTION PRODUCING OPTICAL GLASS AND INSTRUMENTS FOR MILITARY USE, EDUCATION, RESEARCH, INDUSTRY AND EYESIGHT CORRECTION SOUND TROUBLESHOOTING CHARTS ■ We have arranged a special printing of the invaluable sound trouble-shooting charts which supplement the second revision of the sixth edition of F. H. Richardson's Bluebook of Projection. There are 19 practical, detailed charts that provide a simplified guide to quick trouble-shooting, enabling the projectionist to spot and repair sudden breakdowns both in the projection and sound apparatus. A limited supply is available in brochure form at minimum cost. $1 00 POSTPAID QUICLEY BOOKSHOP ROCKEFELLER CENTER NEW YORK OP between reflector and aperture? I really am interested in finding out about this. "I can sympathize with Frank Sheets and his matinee yellow screen. When we were using Strong low-intensity lamps our light would almost look like high-intensity after 10 p.m., yet the amperage and voltage readings would not budge a fraction. The generator would begin to sing, but readings remained the same. We made all kinds of tests but never found the reason for this extra light, nor could the power company find it. "We are at present using 'Cyclex' arc lamps. How does the amount of light compare with a 42-ampere, 27-volt arc? What are the projectionists doing to overcome feeding troubles? "I have discovered a few equipment kinks and I will send them along if you feel that they could be of any mutual help. I know that the ideas of others have always been of assistance in my work and we always are interested in anything that improves our work." This is an interesting letter which I am sure will be instrumental in helping to clarify several points. In answer to the first question, I have investigated the size reflector and type lamp used by the projectionist who asked information on shutter width and find that he was using a Strong Utility H. I. lamp having a 10^4-inch reflector which had an optical speed of f :2.2 and a working distance of 24^4 inches. He was using suprex carbons for which this lamp was designed. There are several lamps manufactured by The Strong Electric Corporation identified by the word "Utility." The lamp using the 11^-inch reflector is the Strong Utility Intermediate high-intensity lamp Type 14050-1. You are correct in assuming that the II ^8-inch reflector should have a working distance of 30 inches, and that the relative aperture or optical speed would be f:2.5. For the benefit of other projectionists using the lamp with the lljHs-inch reflector, the following data are given : The light beam measures 2 15/16-inches in diameter, 5 inches from the aperture at the point at which it is intercepted by the rear shutter of Simplex or Super-Simplex type, and the covering angle is 38° when the distance from the center of the shutter shaft to the center of the light beam is 3 15/16-inches. A reflector set at a relative aperture of f :2.5 requires approximately 98° in each blade of the shutter if the projector is in new condition and does not have too much lost motion between the intermittent and shutter shaft. In answer to your second question, the 40-ampere, 27^2-volt d. c. one-kilowatt arc, and the "Cyclex a. c. one-kilowatt arc operated at 66 amperes, 22 volts ; both produce approximately 4,300 screen lumens without the shutter running when used with a four-element uncoated projection lens of f :2.5 relative aperture. There is no difference in light output. By all means send along your discoveries, "kinks" and ideas, Daniel, for I am sure they will be welcomed by all of us who are honestly trying to do our best.