A photoelectric cell is a light-sensitive device used to measure or respond to light, commonly found in photographic exposure meters. There are two main types: selenium cells, which generate an electric current proportional to the light falling on their surface, and cadmium sulfide (CdS) cells, which change their electrical resistance in response to light.
Cadmium sulfide cells are more sensitive than selenium, particularly in low-light conditions, making them ideal for precise exposure measurement in photography. Photoelectric cells play a key role in achieving accurate exposure, helping photographers capture well-lit, correctly balanced images across a range of lighting conditions.