Posted: May 12, 2017 11:39 am
GrahamH wrote:scott1328 wrote:GrahamH wrote:DavidMcC wrote:
I don't "prefer" to call a yellow square "yellow", I just think it is appropriate when the pixels in it are not resolved (unless you use a magnifying glass), so that green and red areas merge to yellow, so that the avearge physicakl colour is yellow.
And you wanted to make a distinction between perceptual and physical colour? All you are saying here is that you want to call it yellow because you aren't looking at the details and it looks yellow to you. Your reply acknowledges that the photons have wavelengths we would perceive as red and green. If the photons aren't the "physical colour" WTF is?
Even when there are only photons of "yellow" wavelength, they are only perceived (normally) as yellow because they excite the MW and LW cone cells roughly equally. This can also be achieved by a fine mixture of rd and green. (NB, Forget animals with completely different colour vision - they are irrelevant, even from the POV of the names of physical colours.
I will credit you with knowing that mixing "red photons" and "green photons" doesn't create "yellow photons".
If you do some wavelength arithmetic, they would average to yellow photons, doesn't that count?
There would be no yellow photons present. All that counts for perceiving yellow is to have similar excitation of L and M cones and negligible stimulation of S cones, which could result from all sorts of spectra.