Radiant flux (Φe), also known as radiant power, describes the energy emitted over the entire spectral range. The unit for radiant flux is the watt (W). Radiation is visible to humans in the wavelength range between 380 and 780 nanometres. Weighted with the spectral brightness sensitivity of the eye, the radiant flux (Φe in W) becomes luminous flux (Φ in lm).
