Camera exposure time control circuit

An exposure time displaying circuit for a camera comprising:

• a calculation circuit connected for receiving the logarithmic compression values of an object brightness, a film sensitivity, an aperture value and an exposure factor for calculating an automatic exposure time;
• an analog-to-digital converter and latch circuit for analog-to-digital converting and latching an input voltage;
• an oscillator;
• a conter for counting pulses produced by said oscillator;
• a manual exposure time setting circuit for producing digital data corresponding to a manually set exposure time;
• a digital-to-analog converter circuit having an input coupled to an output of said manual exposure time setting circuit;
• a decoder and driver circuit for decoding received digital data for driving a display element;
• a first switching circuit for selectively applying an output of said analog-to-digital converter and latch circuit and an output of said manual exposure time setting circuit to said decoder and driver circuit;
• a second switching circuit for selectively applying an output of said counter and an output of said manual exposure time setting circuit to said digital-to-analog converter circuit;
• wherein for automatic exposure time control, said first switching circuit couples the output of said analog-to-digital converter and latch circuit to said decoder and driver circuit while said second switching circuit couples the output of said counter to said digital-to-analog converter circuit and for manual exposure time control said first switching circuit couples the output of said manual exposure time setting circuit to said decoder and driver circuit while said second switching circuit couples the output of said manual exposure time setting circuit to said digital-to-analog converter circuit.

An exposure time control circuit for a camera for both automatically and manually controlling an exposure time comprising:

• a manually operated switch for producing "on" and "off" control signals;
• an exposure factor setting circuit for setting an exposure factor in the form of digital data;
• and an exposure time setting circuit to set a manual exposure time in the form of digital data;
• and switch means for applying said "on" and "off" signals to said exposure factor setting circuit in an automatic mode of operation and to said manual exposure time setting circuit in a manual mode of operation.