Exposure time control circuit for camera with flash light device

Exposure time control apparatus for a photographic camera of the type provided with an electronic flash light device having means for producing a "ready" signal when said electronic flash light device is in condition to be triggered to emit a flash of light in response to operation of the shutter mechanism of said photographic camera, said exposure time control apparatus comprising light measuring means for measuring the brightness of a scene and for producing a brightness signal representing the measured brightness;

• means for producing a signal representing the sensitivity of the photographic film in said camera;
• means for producing a signal representing the stop size selected for said camera;
• combining means for combining said signals representing measured brightness, film sensitivity and stop size to produce a first exposure signal representing the duration for which the shutter of said camera should remain open to expose said photographic film;
• manually operable exposure means for producing a second exposure signal;
• an exposure time signal generating circuit having a plurality of outputs, each adapted to provide a respective control signal, said exposure time signal generating circuit being selectively responsive to said first or second exposure signal to produce said control signal at the one output thereof corresponding to the selected first or second exposure signal;
• decoder means coupled to said output of said exposure time signal generating circuit to decode the control signal produced at said one output to an exposure time signal;
• digital timing means responsive to the opening of said shutter for generating a digital timing signal, said digital timing signal being changed periodically;
• digital comparator means for comparing said digital timing signal to said exposure time signal to release said shutter when said digital timing signal becomes equal to said exposure time signal;
• and inhibit means responsive to said "ready" signal produced by said electronic flash light device for inhibiting control signals from being supplied to said decoder means except for a control signal representing a predetermined duration for which said shutter should remain open to expose said photographic film to the scene illuminated by said flash of light, whereby said decoder means supplies to said digital comparator means an exposure time signal indicative of said predetermined duration.