The candela per meter squared (cd / m 2 ) is the standard unit of luminance. It represents a luminous intensity of one candela radiating from a surface whose area is one square meter.
Formally, the candela is defined as the magnitude of an electromagnetic field ( EM field ), in a specified direction, that has a power level of 1/683 watt (1.46 x 10 -3 W) per steradian at a frequency of 540 terahertz (540 THz or 5.40 x 10 14 Hz). This is in the middle of the visible-light spectrum.
Luminance is sometimes quoted when specifying the brightness of computer displays. Cathode-ray tube ( CRT ) monitors generally provide greater luminance than thin-film transistor ( TFT ) displays. However, the best criterion for choosing and adjusting a display is the user's own viewing comfort. This will depend on the level of illumination in the room where the display is used.