1980-12-24
1981-12-01
Gellner, Michael L.
354 49, 354 51, G03B 7083, G03B 7099
Patent
active
043033180
ABSTRACT:
An exposure time control device for a camera which measures the light reflected from a surface of a leading shutter curtain and/or a surface of a film can determine exact exposure time even if difference exists between reflection factors of the surfaces, by means of a simple construction including no special light measuring circuit other than a light measuring circuit originally provided for the exposure time control purpose. A first memory or storage capacitor memorizes logarithmically compressed output of the light measuring circuit fed through a first switch when the first switch is opened in conjunction with start of the leading shutter curtain travel while a second storage or memory capacitor memorizes the output fed through a second switch when the second switch is opened in conjunction with completion of the leading shutter curtain travel. An operational circuit combines the output of the light measuring circuit at a time of full shutter opening with the output in the second memory capacitor subtracted by the output in the first memory capacitor, producing a corrected output. A time count circuit controls timing of trailing shutter curtain release in accordance with the corrected signal.
REFERENCES:
patent: 4126366 (1978-12-01), Watanabe
patent: 4131350 (1978-12-01), Uchiyama et al.
Kitaura Mashio
Yamamoto Koji
Gellner Michael L.
Minolta Camera Kabushiki Kaisha
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