Journal of the Society of Motion Picture and Television Engineers (1950-1954)

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center of the picture aperture, the arrow also being projected onto the viewing screen. The picture gate contains only a mirror for bending the light path. As shown by Fig. 3, the single screw A permits removal of the entire lamp mounting assembly, and the screw B releases the complete condenser and heat filter assembly for cleaning. Sound Reproduction The quality of reproduced sound is considerably better from the standpoint of frequency characteristic, signal-tonoise ratio and flutter than that which is usually associated with film-editing devices. The optical-scanning system is substantially the same as that in general use in theater reproducers. The magnetic head is a conventional commercial type. A four-stage amplifier is used for photographic sound reproduction and one additional stage is connected for magnetic reproduction with magneticreproducing equalization provided. The photographic input circuit contains a narrow dip filter tuned to 1 20 cycles to attenuate the light modulation resulting from operating the sound lamp on a-c. This feature combined with the relatively high thermal inertia of the 7.5-amp lamp gives a saitsfactory signal-to-noise ratio for this use. A tone control is provided on the amplifier and its knob appears through the top of the equipment box. An output jack is also provided at this point to plug in an extension speaker to be used with wall projection if desired. Motors The picture film is driven by a variable-speed torque motor which in combination with the foot-pedal resistance control is capable of driving the film at variable speeds from essentially standstill to double normal speed and is instantly reversible while running. The sound film is driven by an induction motor, which is substantially con stant speed, and is equipped with an electrical brake. A circuit is arranged to charge a condenser with rectified a-c from the line. When the foot pedal is released, back contacts on the switch connect the charged condenser to a relay coil and operate it for a short intri\,il which is determined by the discharge rate of the condenser and (lie associated circuit. The relay momentarily connects a second charged condenser across the field winding of the motor, and, depending on the adjustment of a currentlimiting resistor, the motor can be stopped within two picture frames. This type of braking is fully automatic and has the advantage of having no braking torque applied when the machine is turned by the handwheel. In conclusion, it is felt that the Westrex Editer will fill a long-existing need of the motion-picture industry for modernized film-editing facilities with increased efficiency and improved convenience in operation. References 1. F. Ehrenhaft and F. G. Back, "A nonintermittent motion picture projector," Jour. SMPE, 34: 223-231, Feb. 1940. 2. F. Tuttle and C. D. Reid, "The problem of motion picture projection from continuously moving film," Jour. SMPE, 20: 3-30, Jan. 1933. 3. Howard J. Smith, "8000 pictures per second," Jour. SMPE, 45: 171-183, Sept. 1945. 4. J. Kudar, "Optical problems of the image formation in high-speed motion picture cameras," Jour. SMPE, 47: 400402, Nov. 1946. 5. J. L. Spence, "An improved editing machine," Jour. SMPE, 31: 539-541, Nov. 1938. 6. John H. Waddell, "Design of rotating prisms for high-speed cameras," Jour. SMPE, 53: 496-501, Nov. 1949. 7. Charles W. Wyckoff, "Twenty-lens high-speed camera," Jour. SMPE, 53: 469-478, Nov. 1949. Crane, Hauser and Manley: Westrex Film Editer 323