Exposure control circuit for camera of TTL reflective photometry

Details Exposure control circuit for camera of TTL reflective photometry Exposure control circuit for camera of TTL reflective photometry

1982-01-25

1983-01-04

Perkey, William B.

354 31, 354 51, G03B 7083

Patent

active

043670229

ABSTRACT:
An exposure control circuit for camera of TTL reflective photometry type includes a shutter blind of a lower reflectivity than that of a film. The circuit is arranged such that until a given proportion of the film surface becomes exposed as a result of running of a first shutter blind, a correction semiconductor element is rendered conductive to supply a current, which represents a magnified version of minimal current from a photoelectric transducer element when reflected light from the surface of a first blind is incident on the transducer element, the current being supplied to an integrating operation. However, after the given proportion of the film surface has been exposed to increase the magnitude of the photocurrent, the correction semiconductor element is rendered non-conductive, thus allowing an integrating operation of only the photocurrent.

REFERENCES:
patent: 4064517 (1977-12-01), Maitani et al.
patent: 4072961 (1978-02-01), Yamada
patent: 4295720 (1981-10-01), Mizokami et al.

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