Ernst Leitz Wetzlar Gmbh

Leica Camera Ag

Rolf Magel

Walter Bletz

Gerhard Kranz

Robert Denk

Willi Wiessner

Fritz Keiner

Helmut Bill

A device for exposure metering in photographic cameras including a reflector located in the imaging beam path. The surface of the reflector is provided with a reflecting structure whose size corresponds at least approximately to that of the image recording format. At least one photoelectric receiver records the light intensity of a portion of the image reflected from the reflecting structure. The reflector is pivotally mounted in the camera housing such that during exposure metering the reflector surface is in the vicinity of the film plane of the camera. A limited portion of the reflector is transparent and a photoelectric receiver is set into the backside of the reflector behind the transparent portion.

Device for exposure metering

A circuit arrangement for reducing the settling time of amplifiers to which photoelectronic components are connected. A control circuit is provided which, operating in conjunction with components of this circuit arrangement, prevents the parasitic capacitance of the photoelectronic component from being charged up when the circuit arrangement is connected to the operating voltage.

Circuit arrangement for reducing the settling time of logarithmic

A circuit containing a photodiode for determining when there is sufficient illumination for an optical device to operate having provision for compensating signal variations due to temperature-dependent operation of the photodiode by supplying logarithmic means with an input from a potentiometer connected to a temperature-dependent distributor circuit.

Circuit arrangement to ascertain and indicate that a luminous density

In a switching circuit for an electronic exposure meter in optical devices with a photoelectric converter at the input of an amplifier which logarithmizes the output current from said converter, with a temperature compensation circuit and a photoelectric current limit value circuit and with an indicator, a voltage supply source having a main switch, means are provided on the device for coupling to the main switch. These means effect automatic connection or disconnection of the switching circuit to or from the supply source.

Circuit arrangement for an electronic exposure meter

Disclosed is a method and apparatus for automated exposure control in a photographic camera having a lens equipped with an automatically adjusting diaphragm. A measuring signal is provided which is proportional to the luminance of the subject, the sensitivity of the film and the initial aperture at which the diaphragm is set. A control device is provided which stops the moving aperture at its working opening. A reference signal is provided by combining the measuring signal with a signal proportional to a shutter speed limit value. The diaphragm automatic adjustment is initiated and the variation or change in diaphragm aperture is converted to a signal which is combined with the measuring signal. This varying signal is continuously compared with the reference signal and a control signal to stop the automatic adjustment of the diaphragm is issued when the signals being compared are equal. In one embodiment of the invention, the reference signal is provided by combining the measuring signal and the shutter speed limit value in a 1-to-1 ratio. This ratio can be changed to provide either shutter speed or aperture priority if desired.

Method and apparatus for automatic exposure control on a photographic

An arrangement for compensating the temperature coefficient of the semiconductor junction connected in a circuit, comprising first, second, and third transistors of the same predetermined type, each having a base-emitter junction and operatively connected to have a respective collector current, and a resistive voltage divider having two ends in a center tap. The transistors and the divider are operatively connected such that the voltages of the base-emitter junctions of the first and second transistors are summed and applied across the ends of the voltage divider. The voltage from one end to the center tap of the voltage divider is connected across the base-emitter junction of the third transistor. The collector current of the third transistor thus corresponds to the geometric mean of the respective collector currents of the first and second transistors and is substantially less temperature-dependent than the collector current of the first transistor. The arrangement is particularly useful in circuits for exposure measuring and control in photographic devices.

Circuit arrangement for the compensation of the temperature coefficient

A single lens mirror reflex camera with spring biased diaphragm and with exposure metering and controlling system having a central operation mode selection switch for switching between several operation modes, is improved by providing indicators at the camera which are switched in when the 'automatic aperture' operation mode is selected and are recognized as warning displays by the user, and by providing switching means at the stop preselection ring of the objective and at the camera, which turn off the indicators in the camera proper when the smallest aperture is set at the stop preselection ring.

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Fernwald, Germany

Rolf Magel