Comment by palish
15 years ago
What I'm saying is that RGB(128,128,128) is not halfway between RGB(0,0,0) and RGB(255,255,255), in the same way that a 4.0 earthquake is not halfway between a 0.0 earthquake and an 8.0 earthquake.
The scale is non-linear.
As far as I can see, the only true linear space is frequency space --- aka "EM spectrum" space.
I believe this is why a gamma transform is made at presentation time. But maybe what you're interested in is adding RGB tuples before presentation?
What he is trying to do is produce a simple relation between RGB values and EM frequencies; which is not possible. There is no simple relationship there, RGB values are only related to how we see light, how our eyes work, not to the EM spectrum.
I believe what you are looking for is the alpha channel--the fourth color component which specifies how to blend two values. It doesn't make sense to add RGB(0,0,0) and RGB(0.5,0.5,0.5). It does make sense to add RGBA(0,0,0,0) and RGBA(0.5,0.5,0.5,0.5).