Abstract: A circuit for detecting back light comprises a time constant circuit including a capacitor selectively connectable in series with either a resistive element, or one of two CdS photoconductive elements used to measure the central and surrounding portions, respectively, of an object being photographed. Three switches separately conect the resistive element and the two photoconductive elements in series with the capacitor. A circuit generates pulses for a length of time governed by a time constant determined by the time constant circuit, and three separate counters store the pulses the number of which is determined by the time constant. An arithmetic circuit processes the pulses stored in the counters to determine the amount of back light present on the object.

Abstract: A camera capable of multiple exposure photography. The camera has a lens shutter for performing a programmed exposure operation and a diaphragm-adjusting operation and a focal-plane shutter. The camera further includes a first selector means and a second selector means. The operation mode of the camera is switched between a lens shutter mode and a focal-plane shutter mode by the first selector means. In the lens shutter mode, the lens shutter is operated as a programmed shutter. In the focal-plane shutter mode, the shutter speed and the aperture are controlled by the focal-plane shutter and the lens shutter, respectively. The second selector means establishes a multiple exposure photographic mode. Also, the second selector means sets up the lens shutter mode irrespective of the setting of the first selector means.

Abstract: A power circuit for a camera comprising a power activation means containing a release switch for activating the camera, a step-up means for starting to step up the voltage of a battery by the power activation means, a CPU which is driven by an output of the step-up means so as to control the operation of the camera and which has a reset terminal for stopping the operation, and a voltage detecting means for detecting the output voltage of the step-up means and for generating a detection signal when the voltage is lower than a set value which has previously been determined, the set value being set to correspond to the limiting operation voltage of the CPU and, when the output voltage of the step-up means is lower than the limiting operation voltage of the CPU, the CPU being reset and stopped to operate.

Abstract: A camera has a shutter device driveable to undergo opening movement to open an aperture to effect exposure operation according to a given exposure value, and a motor actuatable to rotate at an unstable rotational speed for driving the shutter device. A detector operates after the motor starts rotating and before the shutter device undergoes its opening movement for detecting the rotational speed of the motor. A controller adjusts the shutter device in accordance with the detected rotational speed of the motor to thereby enable the shutter device to effect the exposure operation so as to accurately achieve the given exposure value.