Ballast An auxiliary piece of equipment designed to start and to properly control the flow of power to gas discharge light sources such as fluorescent and high intensity discharge lamps. The term has been retained from the early days of lighting when a standard candle of a fixed size and composition was used as a basis for evaluating the intensity of other light sources. Candlepower Luminous intensity expressed in candelas. Plots of luminous intensity, called candlepower distribution curves, are used to indicate the intensity distribution characteristics of reflector-type lamps. A measure of intensity mathematically related to lumens.
Candlepower is often to measure the intensity of lamps that project light.
Chromaticity Also called Color Temperature. An international system used to rate a lamp's ability to render object colors. A measurement of the color shift an object undergoes when illuminated by the light source, as compared to a reference source at the same color temperature. Color rendering is measured on an index from 0-100, with natural daylight equal to 100. The general term applied to families of smaller diameter fluorescent lamps, some of which have built in ballasts and medium screw bases for easy replacement of incandescent lamps.