Radio age research, manufacturing, communications, broadcasting, television (1941)

TELEVISION RECORDING New Development Permits Filming of Video Programs From Screen of Kinescope Picture Tube, Together with Sound, for Distribution to Non-Network Stations. By Robert M. Fraser Engineering Developinent Group, National Broadcasting Company THROUGH the use of a new NBC development called the Television Recorder, television pro- grams including picture and sound can now be recorded on film direct from the screen of a television re- ceiver for distribution to stations not yet interconnected by coaxial cables and radio relays. As the quality of the basic television image improves, the quality of recordings in kinescope photography will be enhanced to a degree where the average viewer will be unable to tell if the program he is seeing is "live" or "canned." The kinescope recorder method will permit not only the es- tablishment of a coast-to-coast video network before cables or relays are installed but will allow retention of television programs for documen- tary, historical, legal or critical pur- poses in a manner similar to record- ings of radio programs. The development of this recording system was started in 1938 with ex- perimental cameras operating at 8, 15, and 16 frames per second. They were followed by a prototype camera operating at 24 frames per second. This model was the forerunner of the $10,000 i-ecorder cameras in use today. In the earliest experiments, a decade ago, it was found that the amount of light obtainable from available kinescopes was not enough to produce a full exposure on the [10 RADIO AGE] fastest films obtainable at a l/30th second exposure in a 16-frame-per- second camera. The cameras used in the early efforts were spring-motor driven and the shutter rate was not syn- chronous with the frame rate of the television system. This caused a flaw in the pictures called "shutter bar" or "banding" in which a black- and-white bar moved across the film image when projected. Much research work in finding an accurate method of operating the motor-driven shutter in conjunction with the sequence of television images finally led to an acceptable mechanism free from banding effects. Commercial Camera Designed Engineers of the Eastman Kodak Company and National Broadcast- ing Company working together de- signed a commercial camera along the lines of the original model. However, the design of the new camera was complicated by many factors. First the commercial ver- sion had to be able to record a half- hour show with a 1,200-foot load of 16mm film instead of the 200-foot roll used in the first model and in regular Cine Specials. The shutter had to rotate with a minimum of flutter since even a slight change in angular speed resulted in band- ing of the film image. Success even- tually came through the use of a synchronous motor to drive the shutter at the necessary speed through a set of precision gears. Another synchronous motor of larger capacity drives the film trans- port mechanism and the Geneva in- termittent which is the device that pulls down the film strip from one frame to the next. The two motors are kept in step during the starting and stopping periods by an in- genious coupling which allows the stronger of the two motors to assist the weaker until both reach proper speed. The coupling then floats so that there is no physical connection between the motors. Nylon Solves Emulsion Problem Nylon which has a low coefficient of friction is used in the film gate and pressure plate to minimize the accumulation of emulsion from the film, always a source of trouble in motion picture cameras. All friction points in the takeup side of the 1,200-foot magazine are equipped with ball bearings so that takeup of film progresses smoothly from the two-inch core diameter of the empty reel to the 10-inch diameter of the full 1,200-foot roll. Focussing and framing of the pic- ture are carried out by means of a right-angle view finder equipped with a magnifying lens. Visual focussing is done by means of this DUDLEY GOODALE, PIERRE BOUCHERON, JR., AND GEORGE M. NIXON OF THE NBC ENGINEERING DEVELOPMENT GROUP EXAMINE LATEST MODEL OP A TELEVISION RECORDER WHICH RECORDS BOTH PICTURE AND SOUND ON THE FILM STRIP.