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1948-49 Theatre Catalog, 7th Edition, Page 545 (530)

1948-49 Theatre Catalog, 7th Edition
1948-49 Theatre Catalog
1948-49 Theatre Catalog, 7th Edition, Page 545
Page 545

1948-49 Theatre Catalog, 7th Edition, Page 545

FIGURE NUMBER 4. Functional diagram of intermediate h'lm system.

film processing machine, and third, the conventional 35mm theatre film projector. Shown, in Figure 4, is such a system which can be soiintegrated that the film runs through the complete cycle at the conventional speed of 90 feet per minute, completing the cycle so that the elapsed time between the image appearing on the kinescope and its projection

on the viewing screen is less than one minute.

Television Recording

Let us examine each section individually. In Figure 5 we have the special monitor equipment. This consists of a high quality television receiver using a special 5 inch kinescope having a blue

FIGURE NUMBER 5. Television recording equipment.

phosphor screen of high actenic value. The tube, a RCA 5WP11, operates at 27 kilovolts and produces blue images of excellent sharpness and contrast. Since the film used is blue sensitive, the average beam current is. low ensuring long tube life. A negative television image is used on the kinescope screen in order that the film processing will result in a positive image ready for projection.


A special camera had to be devised which would compensate for the timing difference of television at 30 frames per second and motion picture film at 24 frames per second; this camera must also provide for sound on film recording resulting in a single film system.

To illustrate the camera problem refer to Figure 6. The figure is divided into intervals of 1/60 of a second representing the television field frequency. Since the 1/24 second frame rate is 2%. x 1/60, five television fields represent 1/12 second or 2/24 second which is the time interval of two motion picture frames. The problem then is to fit the exposure and the film transport of two film frames into five television fields. If we start to expose the film starting at field ifA" and continuing to the end of field ffBil we have one exposure of 1/30 of a second, a complete interlaced television frame. We have used two fields of the television picture and two more would be required for a second exposure leaving one field out of five to be used for two film transport intervals. This means that half a field or 1/120 of a second is left for each film pull-down. Following the first exposure we allow for the pulldown interval which brings us to the middle of the next television field and it is here that the exposure must begin and continue for another two fields or 1/30 of a second to complete exposure of another film frame followed by pulldown of the film to start a new cycle. The film transport or pull-down interval of 1/120 of a second is one half that of the normal motion picture camera so the faster pull-down is the first special requirement of the camera.

Exposure Control

A precision shutter is required to give the proper exposure on the film. The exposure in terms of the television system must be accurate to less than one half of a scanning line or one part in 30,000. The rigid requirement arises from the fact that the start and stop of the exposure are brought together and a direct comparison is apparent especially in the alternate frames where the splice occurs in the middle of the television field. The shutter motor is specially damped, and the gear train and the bearings have been given special attention to provide exposures of the desired accuracy. The camera and shutter are driven by synchronous motors; it then follows that precise exposure depends on synchronism with the television system, otherwise, the difference in synchronism will change the exposure making an over or under exposure depending on the under or over synchronous speed of the camera. Improper exposure shows up as a band of when the wrong number of a

1948-49 Theatre Catalog, 7th Edition, Page 545