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lation between film transport and shutter opening.
As previously mentioned, no motion of the film in the aperture can be tolerated during exposure, therefore the claw must be free of the film before the shutter opens. The camera is timed, therefore, to open the shutter the moment the claw is free of the film at the end of pulldown.
Figure 4 shows the removable assembly consisting of photocell and pipper lamp, designed for ready removal and rapid replacement of either photocell or pipper lamp. Replacement of either does not disturb shutter timing, and can be done in a matter of seconds, without the necessity of shutting down the camera, should either fail during operation.
Film Gate
During the early development stages of this camera, the usual spring-loaded pressure shoe was used in the film gate to hold the film in the focal plane in contact with the aperture plate, and to obtain the necessary film friction in the
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However, it was believed that if another means could be developed which would provide the necessary film friction during pulldown and retain the film securely at the aperture during exposure, without introducing sliding contact pressure on the emulsion surface of the film, long-time operating conditions would be more favorable. This led to the development of the vacuum-actuated film gate now in use in this camera.
The front half of this device contains the aperture plate, side guide rollers at top and bottom, and a spring-retained shoe supporting the film against the claw during pulldown. The use of a spring-retained surface to back up the film is a desirable safety feature. Should the claw lose registry during a stand-by period, the spring permits the claw to ride over the film during the first pulldown stroke until it picks up the per
Fig. 4. "Plug-in" assembly of photocell and pipper lamp. Note coin-slotted captive screws which anchor assembly in place on camera.
f orations. If there was a solid backing at this point, the claw, once out of registry, would tend to make its own perforations, and would not immediately get back into correct index. It should be understood, however, that the claw does not normally lose index with the film, but because there are no register pins, it can do so if the film is accidently moved within the gate during a stand-by period. The rear half is the hinged part of the gate, and is held closed (or open for threading) by a toggle-action device. A rigidly fastened vacuum shoe replaces the usual spring-loaded pressure shoe directly behind the aperture in this rear half. When the gate is closed, there is a total of about 0.012 in. clearance between the surface of this vacuum shoe and the aperture plate. The vacuum shoe is a rectangular steel plate, about 1 in. wide and % in high. Its center portion, which is centered behind the aperture, is relieved for a depth of 0.010 to 0.015 in. over an area corresponding to the picture. This surface is finished with a flat black lacquer. The rest of the shoe surface is lapped and
Gillette and White: New Video Recording Camera
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