English: Luminous efficacy of a blackbody radiator within 1000 to 16000 Kelvins. The plotted data are derived by integration of Planck function convolved via the CIE 1924 photopic V(λ) luminosity function (equivalent to the y function of the CIE 1931 color-matching functions). Data points are interpolated as cubic splines by gnuplot. The luminous efficacy is given by the left scale and the grid. The right scale shows the luminous efficiency in percent with 100% referring to the visual maximum for monochromatic light at 555 nm and 683 lm/W efficacy.