Indoor artificial lighting: Prediction of the circadian effects of different spectral power distributions.

The study presented in this paper aims to evaluate if and how the environment affects the circadian impact of a light source by predicting circadian stimulus percentages (CS) resulting from the exposure to different light scenes, using equations reported in studies by Mark S. Rea et al. The main findings of this research are: 1) Above 600 lx at the eyes level the increase of CS is little; 2) Between 50 lx and 200 lx at the eyes level an increase of only 50 lx determines a significant increase of CS; 3) Light sources with CCTs between 2900 K and 4200 K have similar impacts on the circadian system according to the calculation method used; 4) Even an almost neutral environment affects the circadian impact of a light source.