converting luminous flux to lumens
Luminous flux in lumens = Radiant power (watts) x 683 lumens/watt x luminous efficacy. The luminous flux is the part of the power which is perceived as light by the human eye, and the figure 683 lumens/watt is based upon the sensitivity of the eye at 555 nm, the peak efficiency of the photopic (daylight) vision curve.he lumen is the standard unit for the luminous flux of a light source. It is an SI derived unit based on the candela. It can be defined as the luminous flux emitted into unit solid angle (1 sr) by an isotropic point source having a luminous intensity of 1 candela.