Light - Much More Than Vision

A brief overview of the impact of light on the circadian system is given, which underscores the importance of developing a framework for circadian photometry. The amount of light, its spectral composition, spatial distribution, timing and duration needed for vision is so different from that needed for circadian functioning, that generalizations about “good lighting” will have to be assessed by two very different sets of criteria in the future. Although the framework provided in this paper will undoubtedly be refined as more research is undertaken, little progress will be made in delivering “healthy lighting” to society until researchers and practitioners begin to consider, measure, calculate, and control the fundamental characteristics of light for the circadian system, as well as for the visual system. It is my belief that a new system of photometry for the circadian system should be developed, and that until we do, we will be unable to lay any claim to “good lighting” with regard to human health.