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. The scaling of the cone fundamentals given below is relative to each originally being scaled to unity peak (as in the corresponding cone fundamental tables).
In terms of quanta for the field size of 10°, VF,10,q(λ) = 0.673905 + 0.356563 , so that:
For to peak at unity, .
In terms of energy for the field size of 10°, VF,10(λ) = 0.692839 + 0.349676 , so that:
To scale to unity peak, .
Note: The MacLeod-Boynton chromaticity coordinates calculated from quantal and energy data are identical. The S-cone coefficient is given to 7 dp so that peak of to one to 6 dp. The peak is at 418.1 nm.
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.
Stockman, A., & Sharpe, L. T. (2000). Spectral sensitivities of the middle- and long-wavelength sensitive cones derived from measurements in observers of known genotype. Vision Research, 40, 1711-1737.