Abstract: A circuit system designed to realize fully digitalized automatic exposure controls is provided in which the read-in brightness information is logarithmically compressed directly into a digital quantity without the aid of any diode element that exhibits a logarithmic characteristic. This enables full utilization of the merits of digitalization while affording further advantages including increased stability against temperature and voltage variations.

Abstract: A circuit for digitally computing the information necessary for controlling the shutter speed or aperture in an automatically exposure-controlled camera is based on a unique algorithm. Based on this algorithm, the shutter speed, for example, can be computed by first generating a number of pulses corresponding to the preset aperture and film speed and deciding to which of three predetermined values this number corresponds. Then the brightness value, which has been separately measured, is repeatedly doubled according to the decision made with respect to the number of pulses generated. The resulting value is exponentially compensated as required to obtain the shutter speed.