Automatic sensitivity controller for electronic still camera

Claim 1

An automatic sensitivity controller for an electronic still camera which performs flash photography, said automatic sensitivity controller comprising: an image pickup device; distance metering means for measuring the camera-to-subject distance; a variable-gain amplifier circuit having a control terminal and amplifying a video signal supplied from said image pickup device at a gain determined in response to a control signal applied to said control terminal; a gain control means for applying a control signal relating to a measured value of the camera-to-subject distance to said control terminal, wherein said control signal output from said gain control means is a dc-voltage signal, said gain control means having: a control voltage producing circuit having a plurality of output terminals through which a plurality of different dc voltages are taken out in parallel with each other; a change-over switch for selectively connecting one of said plurality of output terminals to said control terminal of said variable-gain amplifier circuit in response to a change-over control signal; and switch control means for supplying the change-over control signal relating to the measured value of the camera-to-subject distance to said change-over switch; said automatic sensitivity controller further comprising: an aperture device for adjusting the quantity of light introduced to said image pickup device; aperture value calculating means for obtaining an aperture value by dividing an equivalent guide number determined from the gain of said variable-gain amplifier circuit by the measured value of the camera-to-subject distance; and aperture control means for controlling said aperture device so that the aperture value of said aperture device becomes equal to the aperture value calculated by said aperture value calculating means.