Abstract: The exposure metering circuit comprises a differential amplifier, whose inputs are connected to a measuring bridge consisting of a photo-conductive cell and setting controls for the insertion of exposure factors and whose outputs are connected to light-emitting elements for the indication of a set under-exposure, over-exposure or the correct exposure. The two measuring bridge feed points are connected across a resistor, on the one hand, and across a transistor which is driven by means of a voltage derived from the common emitter circuit of the differential amplifier, on the other hand, to an operating voltage source.

Abstract: A circuit arrangement for the pre-indication of the exposure time to be expected in automatic mirror-reflex cameras in which the brightness of a controllable luminous element, which is constant for the duration of the exposure, is used for the illumination of the photo-receiver of the electronic time-formation system. The voltage dropping over the luminous element, which is proportional to the exposure time, is ascertained by means of a measuring mechanism. The luminous element is formed as luminous diode and in parallel therewith there is connected a current path containing the measuring mechanism fed from a constant current source for the compensation of the response voltage of the luminous diode and for the adaptation of the measuring mechanism to the characteristics of the luminous diode.