Samenvatting
In 1951 the CIE defined the scotopic standard observer V'(h). Up to now there is no standard observer for the mesopic region (10-3-3 cd.mm-²), mainly due to the complicated relation between brightness and luminance. To get some information about luminance in this region the best way is to start with the model of Palmer given in the formulas (3). On basis of this model table 2 gives the apparent changes in efficacies of the light sources SOX, SON, HPL-N and HPI.