The motion picture projectionist (Nov 1931-Jan 1933)

November, 1931 Motion Picture Projectionist 13 scanning cycle as the spot at the transmitting end. The synchronizing means, whereby to keep transmitting and receiving scanning systems in perfect step, takes on various forms. The simplest is the use of synchonous motors operating on a common A. C. power system, since the driving power at both ends is virtually geared by the frequency. Where transmitter and receiver are not utilizing a common A. C. power system, it is possible to make use of a predominant frequency in the carrier wave, which is filtered out, amplified and utilized to actuate an auxiliary motor which accelerates or retards the main motor ever so slightly so as to keep the scanning disc in step with the transmitter. Since standard 60-cycle A. C. systems are almost in perfect step, very little power is required for the necessary acceleration or braking of the receiving scanning disc for perfect synchronism. Two Types of Pickup So much for just the basic principles of television. Returning to program considerations, there are two broad classes of television programs, namely, the direct pick-up and the film pick-up. As the terms imply, the first deals with picking up living subjects either in the studio or outdoors. The second deals with picking up motion picture subjects recorded on film. Direct pick-up, because of inherent difficulties, has been developed more ^B, ■ " : ..**« mw^mwU^SR*' ''-' ^b1 Hi if 1 ■k : < Fig. 2. Projector, Drive Side slowly than film pick-up. Until quite recently, the best television results have been obtained with carefully selected films ranging from the simplest black-and-white or silhouette studies to regular feature pictures. Within the past few months, however, the direct pick-up art has been greatly advanced by improved and refined pick-up apparatus, notably the Jenkins television camera in conjunction with a flood-lighted subject, in place of the flying spot illumination with banks of photo-electric cells. The latest camera is not unlike the motion picture camera. The image PHOTOELECTRIC CELL CONDENSER LENS )djl@ HE LIGHT SOURCE SYNCHRONOUS MOTOR Fig. 3. Graphic Illustration of Pick-up Process is focused by means of a wide aperture lens on to an enclosed scanning disc, which in turn breaks down the image into strips for the photo-electric cells within the camera. The cameraman can tilt or swing the camera, while following the action in a view finder which is, in reality, a monitor radiovisor, reproducing the picked up image exactly as it is being sent to the transmitter. Conditions Encountered With the direct pick-up system we encounter the general conditions familiar to the cameraman. We must have a suitable subject which will provide the desired impression on the sensitive recording means, whether it be photographic emulsion or photoelectric cell. We must have proper lighting so as to secure pleasing lights and shadows. We must have suitable backgrounds. Then there are other requirements such as dressing rooms, properties, carpenters, electricians and so on, all raising the cost of programs to the point where syndication or widespread distribution of programs is economically essential. Unfortunately, there is no available method of transmitting television signals over long wire lines for network syndication. The wide range of frequencies required for pictorial detail cannot be handled over existing telephone lines. Hence the direct pick-up program is limited to a nearby transmitter, and its economics must be worked out on that basis. The direct pick-up has obvious and undeniable advantages. It permits of presenting timely speakers, entertainers, personalities. Ultimately, it must place visual news and sporting events on the air. For the present, however, it is definitely limited to the non-syndicated type of program with its economical restrictions. Moreover, change of locale including scenes impossible of televising by direct pickup, must be presented in some other manner. Film Pick-Up Turning to the film pick-up, we find many immediate advantages to recommend it as the very backbone of the television program. First and foremost, the film pick-up lends itself ideally to syndication. Film produced anywhere, whether in studio or outdoors, can be printed and distributed to any number of associated transmitting stations. Just as the electrical transcription or recorded program brings the finest entertainment to the small broadcaster, so does film bring the finest television entertainment to the remote broadcaster. It takes the place of an elaborate and costly studio, as well as an expensive television studio staff and talent. Properly timed, the program can be simultaneously broadcast to a nationwide audience through a plurality of transmitters. What with air transport and record-breaking flights, the time element in distributing such films is no longer the great drawback it once was. From the standpoint of television technique, the film pick-up permits of excellent detail with the simplest equipment. The subjects may be properly lighted and filmed for television transmission, in the usual motion picture studio or outdoors. In this event the equipment, personnel and experience are already available and add no crushing burden on the infant television industry. Results Very Satisfactory With satisfactory film available, the film pick-up in the television transmitting station faithfully translates the pictorial values into beautifully modulated signals. In the latest Jenkins film pick-up apparatus the image is considerably enlarged and then scanned by a large disc, permitting of far greater precision than in the former practice of scanning the film itself, ^his system makes possible the use of more lines for the scanning system, which in turn spells finer detail. Also, more light can be passed through the film. It is now possible to employ a 240-line scanning system, which provides pictorial detail comparable with the screen pictures obtained with low-priced home projectors. With present direct pickup, it is difficult to go beyond 120-line scanning. The film pick-up comprises a powerful light source, the film itself, a scanning disc and the photo-electric cell, together with the necessary optical system. The light passes through