Photographic camera with an automatic exposure-control circuit i

Details Photographic camera with an automatic exposure-control circuit i Photographic camera with an automatic exposure-control circuit i

1977-03-09

1978-06-20

Hix, L. T.

354 51, G03B 708

Patent

active

040964914

ABSTRACT:
The camera has a shutter release, a shutter, a device responsive to activation of the release for performing a retarded opening of the shutter, and a device operative when activated for causing the shutter to close. The exposure duration is controlled by an exposure control circuit. When the scene brightness level is within a first range, the automatically selected exposure durations are so short that, during a substantial part of the exposure, the shutter is in the process of changing from its closed to its fully open state. When the scene brightness level is within a second range, the automatically selected exposure durations are so long that, during a substantial part of the exposure, the shutter will already be in its fully open state. The exposure control circuit includes first and second light-sensitive elements, used alternatively for scene brightness levels in the first and second ranges, respectively, and first and second electronic switches connected in the current paths of the respective light-sensitive elements for switching one or the other light-sensitive elements into the exposure control circuit. A master-slave flip-flop has an information-signal input, two mutually complementary outputs and a clock input. The two controllable electronic switches have control inputs connected to respective ones of the flip-flop outputs. A brightness-measuring circuit determines whether the scene brightness level is in the first or the second range, and correspondingly applies to the information-signal input of the flip-flop one or the other of two information signals.

REFERENCES:
patent: 4021822 (1977-05-01), Tsujimoto et al.

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