International projectionist (Jan 1959-Dec 1960)

New Strong Electric Corp. 35/70-mm Arclamp Looking toward the future, the Development Section of Strong Electric Corp. has supplied IP with the appended details of its new 35/70 arclamp which was specifically designed to accommodate both the standard 35-mm and the anticipated 70-mm feature film releases. THE recent introduction of several new 70-mm projectors presented a number of complications which had to be resolved in the design of the new Strong "35/70 Special" arclamp. Heretofore, the distance between the film line and the rear of the projector has been fairly standardized in 35-mm projectors, but different dimensional requirements are encountered in many of the 35/70 units. The "35/70 Special." accordingly, had to be designed with an optical system which matched the requirements of all these 35/70 projectors, including the Century, National 70. Victoria X, modified Simplex XL. and Philips. Result: an optical system accommodating a film line to rear of projector distance of from 5 to 9 inches. Prime requisite of an arclamp for 70-mm projection is that it projects a spot which completely covers an aperture more than twice the width of that common to 35-mm projection. Additionally, since higher quality is inherent with and expected of 70-mm. the aperture must be covered more uniformly than usual with the narrower-gauge film. Carbon Size Selection These two factors, while demanding a new optical system, narrow down the choice of elements employed. An example of this restriction is the size of the carbon selected. With a reflector of practical magnification of from 5-7 to 1. only the 13.6-mm positive, burned at from 120 to 130 amperes, affords peak efficiency together with efficient screen uniformity. Incidentally, this carbon probably would have been selected even though greater latitude of size were possible, since the larger crater and greater brilliancy precisely met the demands for full aperture Strong's new 35/70 Special arclamp. coverage and uniform distribution. Notably, an 18-inch diameter Strong Tufcold reflector is employed. Resultant heat at the aperture is so low as to permit projection of the wider print without film damage or buckling, which impairs focus. The greater expanse of screen to be covered and the photographic quality of 70-mm prints dictates that a screen light constant in color temperature be obtained if good picture rendition is to be achieved. Accordingly, the Strong Lightronic automatic arc crater positioner has been integrated in this lamp as standard equipment at no extra cost. Arc Crater Positioning The Strong arc crater-positioning system enables the "35/70 Special" to maintain a screen light of constant intensity and color automatically. The carbons are advanced by means of separate feed motors as the carbons are consumed, to maintain a uniform arc gap length and to position the positive arc crater at the exact focal point of the reflector. A single adjustment controls both carbon feeds. Long experience has enabled simplifying the air-cooled carbon contacts; a water circulator or special plumbing is not required. This reflector-type. 70-mm projection arc accommodates a full 20-inch positive trim of carbon which, burned at 125-130 amperes, permits more than 120 minutes projection time, amounting to as much as an extra full double reel from a single positive carbon. Original, Operating Cost This projection arc is a compatible equipment, since it can be used as efficiently with 35-mm film as with 70-mm film. Without change of reflector, the lamp may be switched from 35 to 70-mm and back, with only a few seconds adjustment. Since the automatic crater-positioning system maintains the positive crater at a predetermined distance from the positive contact assembly for most effective carbon burning, it requires only the turn of a single knob, thus moving the entire arc-burning assembly in relation to the reflector focal point to make the change from 35 to 70 or 70 to 35 projection. This special arc is priced comparable with that of 90 to 135-ampere lain))-. This lamp can now improve considerably 35-mm projection and still be ready to move to 70-mm, regardless of the make of projector. The 13.6-mm carbon, because of its large crater, can be operated at a very low-cost burning rate, while maintaining high screen brightness. Were it possible to employ a smaller carbon with greater magnification for 70-mm projection, the carbon-burning rate and operating cost would be considerably higher. As designed, the cost of operating the "35/70 Special" is not higher than that of many 35-mm lamps. Low current of 120-130 amperes, and the attendant low arc voltage of 58 to 63 volts, will ordinarily effect further saving for the theatre equipping for 70-mm presentation in that in many cases presently-installed rectifier or motor-generator equipment, as well as wiring, may be used with this lamp. William P. White is Named Strong Elec. Field Man The appointment of William P. White as national traveling field representative has been announced by Arthur Hatch, president of The Strong Electric Corp., Toledo, manufacturers of motion picture projection arc lamps, graphic arts equipment, spotlights, and slide projectors. Mr. White is moving his family William P. White, new Strong Electric field representative. to Toledo from Charlotte. North Carolina, where he has been operating the Southeastern Theatre Equipment Co. He has been identified with theatre equipment throughout his business life, and has managed the National Theatre Supply and Wil-Kin Co. branches in Charlotte. INTERNATIONAL PROJECTIONIST • JUNE 1959 Wonders Never Cease High-speed movies have been used as dust-control tool. Locating leaks in dust-control systems often is difficult with standard air-sampling methods. Also, designing control systems is difficult without knowing exact sources and pattern of dust. High-speed movies (500 to 3.000 frames a second ) show where dust originates, where it goes, and shape of dust clouds. 13