> I don’t understand why we can’t teach the color wheel as a true wheel.
Is it even a wheel though?
Is it even a wheel though?
You can distort this shape into a circle but you lose the geometric relationship between chromaticities—two points an equal distance along the circumference of the color wheel don’t necessarily feel “as different” from each other.
CIE XYZ accounts for this by projecting SML excitations down to a 2D plane (XY) and making the third dimension a color-independent luminosity (Z). Since it’s luminosity-independent, the 2D slice is directly analogous to the color wheel.
The issue is more that there isn't really any frequency that only stimulates the M cones. There are some that more or less only stimulate the L cones, but as we get bluer, the stimulation curves of the M and L cones mostly converge, so we can't really get fully independent M cone stimulation (at least not without tricks like locating specific cones and using lasers to stimulate just the M ones, while missing the L ones.) This does indeed make them not linearly independent, so your overall point still stands.