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.