Programed exposure control device

Details Programed exposure control device Programed exposure control device

1980-12-15

1982-04-13

Hix, L. T.

354 23D, G03B 7097

Patent

active

043244670

ABSTRACT:
A programed exposure control device for changeable lens type camera of the type in which the object brightness information is corrected in accordance with other exposure informations including the open F value and the corrected brightness information is ranked to permit the determination of the aperture value in accordance with the rank in a stepped manner and the determination of the shutter speed in accordance with the rank and the brightness information. Said device is further including at least one comparison circuit to compare whether the open F value is greater than the smallest aperture value corresponding to the rank or not. Said device is so constructed as to provide, when the open F value of the lens to be used is greater than the smallest aperture value corresponding to the rank, a shutter speed signal representing a shutter time length which is longer than the shutter time length corresponding to the rank which provides the open-side aperture value closest to the open F value of the lens and to the brightness information, by a time length corresponding to a predetermined light value. The aperture is beforehand set at a constant aperture value which can substantially eliminate the influence of difference of the open F value of the lens. The aperture value for the actual photographing is determined in accordance with the TTL light measurement information at the first-mentioned aperture value, while the shutter speed is determined in accordance with the thus determined aperture value.

REFERENCES:
patent: 3896460 (1975-07-01), Sahara
patent: 3928858 (1975-12-01), Sakurada et al.
patent: 4213682 (1980-07-01), Yamada

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