SU239796A1 - EXPONOMETRIC DEVICE FOR MIRROR PHOTOGRAPHIC APPARATUS - Google Patents

Description

Exposure meters are known for mirror devices, in which the light reception is located on the verge of a single prism in the main beam reflected from a fixed mirror.

The proposed device differs from the known ones in that its photoelectric receiver is connected to a switch, one of the contacts of which is connected to an additional photoelectric receiver mounted on the end of a collective lens with a reflecting surface at an angle of 45 ° to the optical axis.

Such an implementation of the device Ensures the measurement of the integral and local brightness of the object being photographed.

The drawing shows a schematic diagram of the exposure meter.

A beam of light passes the lens /, is reflected from a fixed mirror 2 and falls on a collective lens 3 with a reflecting surface 4 located at an angle of 45 ° to the optical axis.

After that, the beam of light passes on the pentaprism 5, one of the faces 6 of which is made translucent, and then on the ocular p 7.

A photoelectric receiver 8 mounted on the translucent face 6 of the pentaprism, measuring the integral brightness of the object, is electrically connected to

the end of the collective lens 3 is an additional photoelectric receiver 9, which measures the local brightness of the subject, since the semi-transparent surface 4 lies

in the central part of the optical image. The key 10 switches the device from measuring the integrated luminance to measuring the local luminance.

Photodetectors can be included in one of the known electrical circuits, for example. A bridge, with a galvanic device. Another option is to make the photoelectric receiver movable, hingedly mounted on a lever with two

fixed positions: when the lever is rotated, the photoelectric receiver 1 is installed either at the edge of the pentaprism to measure the integrated luminance, or at the end of the collective lens to measure the local

luminance.

Subject invention

An exposure meter for mirror photographic devices containing a mirror mounted behind a shooting lens, a collective lens and a viewfinder pentaprism, at one of the faces of which a photoelectric receiver is installed, characterized in that

of the object being photographed, the photoelectric receiver is connected to a switch, one of the contacts of which is connected to an additional photoelectric receiver mounted on the end of the collective lens, which is partially inside, reflects a surface at an angle of 45 to the optical axis.