Candela (cd)
From The Glossary of Digital Photography
The base unit of luminous intensity in the SI measurement system. It has been defined by the 16th General Conference of Weights and Measurements since 1979 as: 'The luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 x 1012 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. The frequency chosen is a green that the human eye is most sensitive to. A common candle produces about 1 cd, while a 100-watt light bulb produces about 120 cd. See also candle-meter; lux
