Electrical exposure control devices for use with a photographic camera

Claim 1

An electrical exposure control device for use with a photographic camera of the type having a light receptive element for receiving light through the objective lens and means movable prior to shutter actuation from a first to a second position in response to shutter release operation and wherein light measurement is made with said movablE means in said first position and light is blocked from said light receptive element with said movable means in said second position, comprising: means including said light receptive element for generating a first signal proportional to the logarithm of the light received by said light receptive element; means for storing said signal; first switching means for connecting and disconnecting said means for generating respectively to or from said storage means; means for operating said first switching means prior to actuation of said movable means; means for generating a second signal proportional to the inverse logarithmic transformation of said stored first signal; a second switching means for initiating operation of said means for generating said second signal simultaneously with the initiation of shutter opening; means for integrating said second signal; means for effecting shutter closing when said means for integrating reaches a predetermined level; and said means for generating said second signal comprises a transistor, said first signal is a voltage, said second signal is a current, said first signal is applied to the base of said transistor for generating said current in the collector thereof with said first switching means connecting said stored voltage to said base; and further comprising a power source, said second switching means connecting the emitter of said transistor to said power source with the initiation of shutter movement, said means for integrating is a capacitor and the collector of said transistor is connected to said capacitor.