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August, 1952
KEMP : NEW TELEVISION RECORDING CAMERA
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aperture plates with sound and silent register pins are provided.
Tests showed that the gate stability was best when the silent aperture plate was used. With sound film variations in registration tended to occur on the side remote from the register pins.
The 90° pull down required was obtained by driving the triangular cam mechanism used with a shuttle gate at twice the normal speed and utilizing every other stroke only. This gives a pull down in 60°, and leaves 15° each side of pull down for moving the shuttle gate.
(v) Viewfinder
This of the " through the film " type, using a prism behind the gate. As mentioned earlier, it is possible to illuminate the gate by this prism so that the camera can be used as a projector. While recording the viewfinder is seldom used as once camera and cathode-ray tube have been aligned relative movement is unlikely to occur. Even the initial alignment is usually done by projecting the gate aperture on to the cathode-ray tube.
(vi) Driving Motor
This is a 4-pole 1500 v.p.m. synchronous motor coupled Jh
directly to the triangular cam shaft so that the rotor acts as a flywheel. The stator is rotatable through 270° to adjust the relative phasing with the television signals. . I
(vii) Phasing Indicator
A disc with one witness mark on its circumference is mounted on a motor-shaft. This is illuminated by a neon lamp (see Figs. 4 & 5) which is driven from the television frame synchronising pulses in such a way that one flash occurs at the start of every frame sup
Fig. 5. 16 mm. T. V. Recording Camera {reverse view).
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pression period. The duration of the flash is so short that movement of the witness mark is arrested, and the position of the motor at the commencement of the frame suppression period indicated.
(viii) Film Magazine
This is a 16 mm. version of a standard 35 mm. magazine. The film capacity is 1 ,000 feet, and the light traps are of the three roller type. The take up is by friction disc and direct gear drive, as trouble has been experienced with the more usual belt drive.
(ix) Sound System
This was of the variable area type, using noise reduction, and was provided by RCA Photophone Ltd. The question of sound recording for 16 mm. is still under consideration, and it may be that ultimately synchronised magnetic tape will be employed. This has the advantage of providing a high quality master from which 16 mm. married prints can be made by re-recording, thus eliminating the printer losses.
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