Abstract
This paper discusses the effects of lighting systems on involuntary human action. It shows that objective orientation is largely a function of the visual stimulus, and that safe reactions to environmental hazards are therefore dependent on specific lighting distributions. The orientation reflex is described in some detail and its remote effects in the body illustrated by an experiment on muscular tension. The use of the flux diagram in avoiding lighting distributions that generate inadequate visual clues is described, and typical situations involving misleading visual clues are illustrated. Data are also given with respect to safety lighting levels, and a revision of our thinking on this phase of the subject is indicated.