The MacAdam gamut limits are the gamut of all colors that can be reflected by
any ideal surface. It's somewhat wider than Pointer's gamut which is more real
world. Here's a description:
https://philservice.typepad.com/Pointer_MacAdam_Wide-Gamut_Displays_v2.pdf
Three "wide-gamut" RGB color spaces - AdobeRGB, DCI-P3, and Rec. 2020 - are
compared to the gamut of real surface colors (Pointer's gamut) and the optimal
color solid (MacAdam limits).
