CdS — Cadmium Sulphide: in photographic terms, this refers to an electronic light meter using a CdS light-dependent resistor as a sensor. These became common in the early 1970s, largely replacing the less sensitive Selenium meters. Unlike Selenium, which was powered by light, these meters required a battery, and were sufficiently power-hungry that the meter needed to be switched on for as short a time as possible. Thus CdS meters need some sort of switch, where Selenium meters were just left to run all the time.

Glossary Terms
Community content is available under GFDL unless otherwise noted.