as 30 to 50% reduction in the energy use comparing to the high pressure sodium lights. Mesopic weighting function The mesoscopic weighting function at wavelength can be written as the weighted sum, , where is the standard photopic weighting function (peaking at 683 lm/W at 555 nm) and is the scotopic weighting function (peaking at approx. 1700 lm/W at 507 nm). The parameter is a function of the photopic luminance . Various weighting functions are in use, for blue-heavy and red-heavy light sources, as proposed by two organizations, MOVE and Lighting Research Center (LRC). Some values for are shown in the table below. References Eye Vision