# US 4,394,078 A · Method of controlling exposure

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- Number: US 4,394,078 A
- Document ID: US4394078A
- Status: Granted
- Kind: A
- Application number: 06/193,155
- Filed: 1980-10-02
- Granted: 1983-07-19
- Earliest claimed: 1979-10-03
- Assignees: Fuji Photo Film Co., Ltd.
- Inventors: Takaaki Terashita
- Web page: https://patentgrep.com/patent/US4394078A

## CPC

- G03B 7/091: Digital circuits
- G03B 7/09972: {using the mirror as sensor light reflecting or transmitting member}
- G03B 7/28: Circuitry to measure or to take account of the object contrast
- G03B: APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR (optical parts of such apparatus G02B; photosensitive materials or processes for photographic purposes G03C; apparatus for processing exposed photographic materials G03D)

## Abstract

The exposure of a camera is controlled based on the scene brightness measured by use of a number of light measuring elements located at positions to receive light through from the scene. The light receiving area is divided into several zones. In each of the zones, at least one light measuring element is provided to measure the brightness of the scene in each zone and are used to give the maximum or minimum brightness (Bzi) in each zone. Exposure is controlled based on a weighted mean value ##EQU1## (K.sub.i+2 is a coefficient). In a preferred embodiment of the invention, another brightness (B.sub.0) such as a simple mean value of the outputs of all the light measuring elements is obtained, and the exposure is controlled based on the scene brightness B determined by the formula of ##EQU2##

## Claims

### Claim 1

A method of controlling exposure for a camera based on the scene brightness measured by light measuring elements comprising the steps of;
dividing a light measuring area in a camera into a plurality of zones,
providing at least one light measuring element in each of said zones,
obtaining the maximum or minimum brightness (Bzi) in each of said zones,
obtaining an average brightness (B.sub.0) from the outputs of all the light measuring elements provided in said light measuring area,
obtaining a weighted sum of the brightness based on a formula of ##EQU5## where K.sub.i+2 is a coefficient and n is the number of the zones, computing a scene brightness (B) by use of a formula of ##EQU6## where K.sub.1,K.sub.2,K.sub.i+2 are coefficients, and controlling exposure of the camera based on the scene brightness (B).