Comfortable level is an essential element that has considerable implications on human circadian rhytms and the perception of the environments. Light has been defined only in terms of the human visual system, not the circadian system. Light parameters should consider the needs of both the visual and non-visual systems. Discussed are the lighting characteristics impacting these two systems and the implications for designing light for various healthcare and medical applications. The paper describes the experiment conducted in climate chamber of Dresden technical university. The results of this experiment allow to elaborate smart lighting control system that is able to adjust to human perception and circadian rhytms.