Exposure control device

Claim 1

An automatic exposure control device for a camera, said device being capable of accomplishing at least the aperture dominant exposure control operation, the shutter dominant exposure control operation and manual exposure control operation, said device being of the type having a logarithmic compression circuit for developing voltages V E , V D , V A and V B dependent on the APEX indicating quantites Av, Tv, Sv and Bv, respectively, of aperture level A, manual exposure time T, film sensitivity S and brightness of an object B, so as to carry out the APEX operation in accordance with the relationship of Av + Tv = Sv + Bv; shutter speed control means for said camera having an input circuit means, said shutter speed control means being adapted to control the shutter speed in dependence upon the voltage applied to said input means, an aperture level determining means selectively operative to start adjustment of the aperture mechanism of said camera in response to the shutter release operation of said camera and to carry out said adjustment at a predetermined speed; said logarithmic compression circuit means including an aperture transducer means coactive with said aperture level determining means to develop said voltage V E dependent upon the Av quantity; the improvement being characterized by, (a) automatic aperture circuit means responsive to the voltage corresponding to the Bv, Sv and manually set Tv quantities for stopping the aperture level determining means when the aperture mechanism is closed down an amount to cause said developed voltage V E to become equal or greater than (V A +V B -V D ), said automatic aperture circuit means being selectively connectable and disconnectable with said aperture level determining means for shutter dominant and aperture dominant operations, respectively, (b) switchable shutter circuit means for selectively applying to said input circuit of said shutter control circuit, a voltage dependent directly upon V D for shutter preferred operation and a voltage dependent upon (V A +V B -V E ) for aperture preferred operation, and (c) indicator means connected to said logarithmic compression circuit for selectively operating as an aperture indicator and a shutter speed indicator.