American cinematographer (Jan-Dec 1949)

as an important factor. The motion picture camera can be equipped with RCA sound recording equipment to place the sound track and picture on the same film, or the sound signals may be fed to a separate sound recorder which permits editing, re-record¬ ing, and dubbing. MAGNETIC SOUND ( Continued from Page 206) movie amateurs had attempted to satisfy their desire for sound through use of sound on discs and record playing turn¬ tables. The culmination of the Foundation’s efforts to perfect a method of application of magnetic sound to 8mm. movies is told by Dr. H. A. Leedy, Director, Armour Research Foundation, in an article in a recent issue of the Foundation’s publica¬ tion Frontier, part of which is reprinted here: "The possibility of recording sound di¬ rectly on 8mm. motion picture film has always been intriguing to motion picture engineers and to others interested in the field of sound recording. Attempts in the past to record sound on 8mm. film have proved unsatisfactory primarily because of the small space available for the sound track and because of the very low film speed — approximately 2.7 in. per second. "The development and improvement of recording heads and magnetic powder has made possible for the first time the satisfactory recording of sound on 8mm. film. In 35 mm. sound film the optical track is 0.100 in. wide and is well re¬ moved from the sprocket holes and edge of the film. This is, of course, necessary for optical recording since uneven de¬ velopment in the neighborhood of the sprocket holes and the edge of the film results in a distortion of the optical track. "A magnetic track can be used instead of the optical track on 35mm. film. With improved magnetic powders, it is possible to obtain high-quality magnetic records on 35mm. film. Recent experiments have shown that at 24 frames per second it is easily possible to obtain a reproduced sig¬ nal having a signal-to-noise ratio in ex¬ cess of 45 db and a frequency response which is flat within plus or minus from 50 to 16,000 cycles per second. "For 16mm. sound film the sprocket holes have been removed from one edge of the film to make space for the optical track. This optical track can be replaced by a magnetic track, or, on 16mm. silent film, the magnetic track can be placed between the sprocket holes and the edge of the film. In either case, at the same film speed, the results are equally satis¬ factory. "For 8mm. silent film, the sprocket VARIABLE SPEED MOTOR with TACHOMETER for CINE SPECIAL CAMERA AND MAURER CAMERA • 115 V. Universal Motor — AC-DC • Variable Speed 8-50 Frames • Separate Base for Cine Special • Adapter for Maurer Camera Interchangeable Motors: 12 Volt DC variable Speed 8-50 Frames. 115 Volt AC 60 Cycles, Synchronous Motor Single Phase. 220 Volt AC 60 Cycle, 3 Phase, Synchro¬ nous Motor. Animation Motors for Cine Special. Maurer and Mitchell Cameras. Motors for Bolex and Filmo. Cameras. Time Lapse Equipment. National Cine Equipment, Inc. 20 WEST 22nd St. NEW YORK 10, N. Y. ART REEVES’ NEW ADDRESS: ART REEVES MOTION PICTURE EQUIPMENT AND CAMERA SUPPLY COMPANY 7512 Santa Monica Blvd., Hollywood 46, Calif. Only Art Reeves Can Sell The New Model SENSITESTER Will Handle Modern Fine Crain Film. SYNCHRONOUS MAGNETIC C O R D E R S PLEASE SEND FOR BROCHURE 3 5 0 3 B WEST OLIVE AVENUE • BURBANK, CALIFORNIA June, 1949 American Cinematographer 219