Trichromatic approximation method for surface illumination

The problem of approximating the tristimulus coordinates of light reflected from a surface from those of the source and the surface is considered. A variation on a well-known and widely used approximate method for accomplishing this task is presented. This variation uses the XYZ primaries that have unique properties that yield a straightforward analysis of the approximation error. We develop the notion of a calorimetric seminorm and derive an error bound by using techniques from functional analysis. This approach gives some useful insight into the factors that affect accuracy.