A camera having a digitally operating structure for determining exposure time according to a digital value corresponding to the light intensity. The camera also has an adjustable diaphragm. The latter is adjusted in accordance with the difference between the digital value used for determining the exposure time and the actual value of the light intensity where the latter does not coincide with the digital value for the exposure time, so as to increase the precision of the exposure.

The invention provides a charging rate adjusting circuit for a cell combination 1 comprising cell modules 11 each comprising one or a plurality of cells and connected in series and adapted to uniformize the cell modules 11 in charging rate. The adjusting circuit comprises a pair of discharge lines 12, 13 extending from opposite electrodes of each cell module 11, a discharge resistor 2 and an on-off switch 3 provided between the discharge lines 12, 13, a timer circuit 4 comprising a CR circuit for feeding a control signal to a gate of the on-off switch 3, and a photocoupler 5 for initiating the circuit 4 into operation in response to a discharge command.

A device which determines the exposure time in a camera for a sensed scene brightness and in accordance with exposure time factors such as the ASA number of the film and the f-stop setting. The brightness of the scene is converted into a pulse train which is fed into a binary counter which develops the exposure time count. A switch is settable in accordance with the exposure time factors changes the input position of the pulse train into the counter thus varying the magnitude of the exposure time count for the number of pulses in the pulse train. The exposure time corresponds to the mangitude of the exposure time count and thus is determined in accordance with the brightness of the scene bring photographed and the predetermined exposure time factors.

In a photographic camera having programmed automatic exposure control, a light measuring output is produced by measuring scene light and an exposure value signal is generated in response to the light measuring output. A time value and aperture value signal are automatically varied as a function of the changes in the exposure value signal, which function is adapted to be altered in a predetermined manner by the change in the exposure value signal. The aperture size is determined in response to the size in the aperture value signal and the exposure time is determined in accordance with the time value signal.

An electronic camera shutter control circuit having an indicator for indicating when the camera shutter is open. A circuit responsive to a control signal controls a current flow through an electromagnet which is energized during the opening of the camera shutter to prevent the shutter release mechanism from closing the shutters. An indicating element indicates that current is flowing through the electromagnet and therefore indicates that the shutter is open. A control circuit having a photoresponsive element develops a control signal determined by the brightness of the scene to be photograhed and applies the control signal to the circuit responsive to the control signal. The control circuit includes a capacitor which is charged at a rate determined by the conductivity of the photoresponsive element which varies according to the light sensed. When the voltage stored in the capacitor exceeds a predetermined value, the circiut responsive to the control signal deenergizes the electromagnet so that the camera shutter closes. The circuit responsive to the control signal comprises a pair of transistors with their respective emitters connected to the indicator.