Preflash measurement technique

Details Preflash measurement technique Preflash measurement technique

1989-09-29

1991-03-05

Gellner, Michael L.

G03B 700

Patent

active

049981285

ABSTRACT:
An automatic exposure system for an electronic flash camera incorporates an arrangement for measuring the reflectivity of a scene illuminated by the electronic flash prior to exposure in order to determine certain photographic scene characteristics for use in controlling a subsequent photographic exposure, an arrangement that substantially reduces the complexity and energy consumption of the electronic flash system while improving the ability of the exposure control system to accurately determine these characteristics. The arrangement includes the pre-exposure firing of the electronic flash to illuminate a scene with a pulse of light for a short, fixed period of time. A reflection of this light pulse is integrated for a portion of this fixed period of time. The final integrated value of the reflected light is a measure of subject reflectivity. This integrated value is then employed to derive the desired photographic scene characteristics.

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