Exposure control system having dual mode photodetector

Details Exposure control system having dual mode photodetector Exposure control system having dual mode photodetector

1985-05-02

1986-12-30

Adams, Russell E.

G03B 7099

Patent

active

046325425

ABSTRACT:
An exposure control system for a photographic camera of the type employing a scanning type shutter, a controllable source of artificial illumination and a photodetector for sensing scene brightness levels both prior to and during film exposure preferably includes a light diffuser that is automatically movable, in response to a selected camera function, between a first position where it can collect scene radiation from a field of view substantially greater than that of the photodetector and then direct the collected radiation along an optical path onto the light sensitive surface of the photodetector, and a second position displaced from the photodetector where the diffuser has no effect on the amount of scene light measured by the photodetector. Scene brightness level is normally measured before actual film exposure in order to determine the amount of artificial illumination that must subsequently be added to the scene during film exposure and is measured during film exposure to control the extent of shutter blade opening for proper film exposure. By increasing the effective size of the viewing angle over which scene brightness level is measured prior to exposure, the photodetector is precluded from classifying an otherwise low light level scene as a high light level scene if a relatively bright, but localized light source should be present in the scene to be photographed, thereby avoiding the possibility of an underexposed photographic image being caused by such a localized light source.

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