PHOTOMETRIC STANDARDS

PHOTOMETRIC STANDARDS
The candela-The standard candle has been redefined as the new candle or candela (cd). One candela is the luminous intensity of 1/60 of 1 of the projected area of a black body radiator operating at the temperature of the solidification of platinum (2045 K). The candela emits one lumen per steradian (1 lm sr-1).

Note that the luminous intensity emanating from a source with a spectral distribution that differs from that of the standard candle may be evaluated by using a sensor whose relative spectral response is identical to that standardized for photopic vision.

The lumen-The lumen (lm) is defined in. terms of the candela. The luminous flux per steradian from a source whose luminous intensity is 1 candela is 1 lumen.