and form rendition, views, and the temporal lighting qualities may justify this careful design requirement and additional analyses.

LIGHTING AND ITS IMPACT ON THE VISUAL AND CIRCADIAN SYSTEMS

When evaluating the performance of any lighting system, electric or daylight, its impact on two biological systems—the visual and the circadian—needs to be considered together with the physical attributes of light that differentially affect these systems (Figure 4.1).

FIGURE 4.1 Light as it affects human performance and health through the visual and circadian systems. SOURCE: Lighting Research Center.

The Visual System

The visual system functions as a very quick remote-sensing mechanism that alerts us to changes in the environment and enables us to identify threats and opportunities around us. The visual system is fairly well understood for normal adult populations in regard to the effects of light on both appearance (what things look like) and visual performance (how well



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