Abstract: A novel photometric circuit for a camera is disclosed wherein the operational amplifiers common to conventional photometric circuits are eliminated from that part of the circuit which solves the exposure Apex indication equation: S.sub.v + B.sub.v = A.sub.v + T.sub.v. The variable resistors which are used to convert the film sensitivity and aperature settings into electrical quantities are positioned in the feedback circuit of the transistor which is connected to the electro-optical transducer and which develops a voltage dependent upon scene brightness.

Abstract: A camera which is capable of automatically determining exposure time and which is also capable of providing for manual determination of exposure time either in a manual-mechanical range of exposure times or in a mechanical-electrical range of exposure times. The automatic exposure-time determining structure includes an electromagnet which is energized when the shutter is opened and which is deenergized to bring about closing of the shutter so as to terminate an exposure.

Abstract: A circuit for disabling the LED display L1-L5 in the light meter of a single lens reflex camera in response to mirror movements. When the mirror 21 is raised the switch 17 is closed which reverse biases the LEDs. After the mirror is lowered the switch 17 is opened to enable the LEDs, but a short time delay is provided to allow transients to settle out by reason of a capacitor 18 which must first charge through a grounding resistor 19.

Abstract: An SLR camera includes a light measuring and computing circuit 1-7 whose output is fed to a comparator 8 together with the analog output of a D/A converter 12 coupled to a bidirectional counter 13. The counter is servo-loop driven to achieve circuit balance through AND gates 10, 11 in response to the comparator outputs, and the decoded counter outputs energize an appropriate LED display element L1-L16. The AND gates are disabled by the closing of switch 17 in response to the raising of the reflex mirror, to thereby lock the counter and display and prevent fluctuations therein. A capacitive time delay may be provided after the reopening of the switch following the lowering of the mirror to allow circuit transients to settle out.