Citation

Rea MS, Figueiro MG, Bierman A, Bullough JD. J. Circadian Rhythms 2010; 8(1): 2.

Affiliation

Lighting Research Center, Rensselaer Polytechnic Institute, 21 Union Street, Troy, NY 12180, USA. ream@rpi.edu.

Copyright

(Copyright © 2010, Holtzbrinck Springer Nature Publishing Group - BMC)

DOI

10.1186/1740-3391-8-2

PMID

20377841

PMCID

PMC2851666

Abstract

The present paper reflects a work in progress toward a definition of circadian light, one that should be informed by the thoughtful, century-old evolution of our present definition of light as a stimulus for the human visual system. This work in progress is based upon the functional relationship between optical radiation and its effects on nocturnal melatonin suppression, in large part because the basic data are available in the literature. Discussed here are the fundamental differences between responses by the visual and circadian systems to optical radiation. Brief reviews of photometry, colorimetry, and brightness perception are presented as a foundation for the discussion of circadian light. Finally, circadian light (CLA) and circadian stimulus (CS) calculation procedures based on a published mathematical model of human circadian phototransduction are presented with an example.

Language: en