cell

Definition: (1) Part of a lens barrel or optical system holding one or more lenses or groups of lenses e.g. front cell focusing. (2) Unit or element of detector for light or other radiant energy e.g. photo-diode of exposure meter. (3) Unit or element whose electrical resistance varies with incident radiation; used in an instrument for measuring light e.g. CdS cell of exposure meter. (4) Unit that temporarily stores electrical energy, usually as part of a battery.

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