Samenvatting
This paper analyses the work relating to the visibility curve as well as to spectral efficiency of radiation in regard to visual acuity and contrast sensitivity. Methods of calculation of the visual efficiency for various types of light sources are presented. The results of an investigation of the brightness-luminance relation are analysed. Recommendations recording the photometric conditions for the small luminance range are indicated. Certain physiological characteristics of the spectral sensitivity of the eye are examined.