Illumination engineering applies photometry, optics, electrical design and controls to place useful light where people need it. Lighting calculations distinguish luminous flux in lumens, luminous intensity in candelas, illuminance in lux and luminance in candelas per square metre. These quantities describe different parts of a lighting system and should not be used interchangeably.
The articles below cover light theory, lamp operation, source types and lighting schemes. A design also needs suitable illuminance, distribution, glare control, colour appearance, colour rendition, flicker performance, controls and maintenance. Compare source efficacy with complete-luminaire efficacy, because the driver, optics and fixture affect delivered light and energy use.
