Electric lens

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Pentacon electric 2.8 / 29, There are three contact pins on the lens for transferring the set aperture and a metal pressure pin for mechanical stopping down
Praktica LLC (1969) with the Pancolar 1.8 / 50 lens removed, making the automatic iris contacts visible

The so-called. Electric lenses are in the L-series (models LLC, PLC2, PLC3, VLC2, VLC3, EE2, EE3 ...) of the Praktica -Kleinbild SLR of VEB Pentacon used around the aperture metering to allow, together with an automatic exposure control. When setting the desired working aperture, an electrical potentiometer is adjusted, i.e. the aperture value is assigned an electrical resistance value that is transmitted to the exposure meter in the camera housing with the help of three contacts. During the exposure measurement, which takes place through the lens ( TTL exposure measurement ), the aperture can remain fully open so that the viewfinder image remains bright.

However, the depth of field associated with the working aperture in the viewfinder image cannot be assessed. To make this possible, the electric lenses can be dimmed with a slider (A / M) on the work screen.

The electric lenses have an M42 thread connection, so conventional M42 lenses can also be used on the L-series cameras, but only with aperture measurement.

Most other interchangeable lens 35mm SLR cameras with open aperture metering and automatic exposure have bayonet or thread connections and no automatic exposure.

Working principle

When the aperture setting is changed, the position of the tap on the potentiometer changes and with it the electrical resistance. The resistance ratio forms a measure for the aperture value and is evaluated in a bridge circuit .

Examples of electric lenses

Praktica EE2 with lens Pentacon electric 1.8 / 50 MC; 1977
  • from Jena electric MC Flektogon 2.8 / 20 (also labeled with Carl Zeiss Jena)
  • Pentacon electric 2.8 / 29 MC
  • from Jena electric MC Flektogon 2,4 / 35 (also labeled with Carl Zeiss Jena)
  • Pentacon electric 1.8 / 50 MC
  • from Jena electric MC Pancolar 1,8 / 50 (also labeled with Carl Zeiss Jena)
  • from Jena electric MC Pancolar 1,8 / 80 (also labeled with Carl Zeiss Jena)
  • Pentacon electric 2.8 / 100
  • Pentacon electric 2.8 / 135 MC
  • Zeiss electric Sonnar MC 3.5 / 135 (also labeled with Carl Zeiss Jena)
  • Zeiss electric Sonnar MC 2,8 / 200 (also labeled with Carl Zeiss Jena)
  • Pentacon electric 4/200