The luminous flux and the radiation power, luminous flux is mainly human feel light power. A large number of people with normal vision, the vision of the most sensitive wavelength is about 555.0nm the green light, the human nature of the wavelength spectrum sensitivity of different visual function by V (lambda) light said. Is the amount of radiation power with visual function V (lambda) physical quantity weighted. The provisions of the international unit of luminous flux, the symbol is Phi units, lumens (LM).
Refers to the luminous flux per unit time by the light emitted by the light source, representing a total amount of light emitted by the light emitting body, the unit with the lumen said. Calculation is the radiant flux through the visual function. One lumen is equal to one candle uniform point source radiation for a solid angle radian in the light flux.
In general, you can use a spectrometer to match an integrating sphere or to use a light meter to measure the flux
The luminous flux represents the total power of light; unit of luminous flux is the lumen (lm). The formula is Radiant flux multiply Luminosity function.