The luminosity (luminous flux) indicates the amount of light produced by a lamp. In illuminants that emit all-round light, the luminous flux is specified in lumen (lm). In reflector lamps, which emit focused light in one direction, the light intensity for certain beam angles is given in candela (cd). The nominal luminous flux denotes a numerical value for the identification of the illuminant, the rated luminous flux the measured value.

See also:

Luminous Flux
Reflector illuminant