MacLeod-Boynton chromaticity coordinates based on the Smith & Pokorny cone fundamentals.
The MacLeod-Boynton chromaticity coordinates are defined as:
, and ,
where , and are the three cone spectral sensitivities scaled so that (i) , and (ii) peaks at one. Traditionally, the Smith & Pokorny and cone fundamentals are already scaled in this way.
In a space where Cartesian coordinates represent the excitations of the three cone types involved in color vision, a plane of constant luminance provides a chromaticity diagram in which excitation of each cone type (at constant luminance) is represented by a linear scale (horizontal or vertical), and in which the center-of-gravity rule applies with weights proportional to luminance (see p. 1183 of MacLeod & Boynton, 1979).
MacLeod, D. I. A. & Boynton, R. M. (1979). Chromaticity diagram showing cone excitation by stimuli of equal luminance. Journal of the Optical Society of America, 69(8), 1183-1186.
Smith, V. C. & Pokorny, J. (1975). Spectral sensitivity of the foveal cone photopigments between 400 and 500 nm. Vision Research, 15, 161-171.