ABSTRACT
In addition to ensuring people can see what needs to be seen, most lighting installations are designed to ensure visual comfort. But what is visual comfort? One view is that visual comfort is simply the absence of visual discomfort. This is logical but not particularly helpful. While it is undoubtedly true that some lighting conditions can cause discomfort, is it also true that there is a positive sense of comfort to be manipulated after all sources of discomfort have been eliminated? Zhang et al. (1996) and Helander and Zhang (1997) examined the question of perceptions of comfort and discomfort for seating. They found that perceptions of comfort and discomfort were independent of each other, rather than a continuum. Specifically, the perception of discomfort experienced when sitting was characterized by feelings of pain, soreness, and numbness that changed over time and could be related to the physiological stresses the seating produced. Perceptions of comfort were related to feelings of well-being and esthetics that changed little over time, and could be linked to perceptions of luxury and plushness. Applying this framework to lighting suggests that the most of the recommendations made by authoritative bodies about desirable lighting conditions are concerned with eliminating visual discomfort while how lighting designers make a living is to provide visual comfort. This chapter is devoted to the topic of light and visual discomfort.
