XYZ functions and cone sensitivities appear to play little role in visual perception in that colour computation does not appear to be carried out in cone or XYZ coordinates. In its first incarnation, spectral sharpening was proposed as a method for finding the color space, a linear combination of the cones, that best supported adaptation by a von Kries type model. The term sharpening is used because the resultant sensitivities have narrower support compared with the cones. In this paper we show that spectral sharpening also helps us to understand metamerism and color matching.