From the Wiki site (Thanks Mark, Guillermo, Rich):
RGB Saturation = 1-(Min/Max).
(other color mode equations will be different, I'm sure)
I sampled a green pixel and obtained these RGB values: R 53, G 64, B 85
Minimum is the Red component at 53. Maximum is the Blue component, at 85.
53/85 is .6235.
1-.6235 is .3765,
which rounds up to 38 and is expressed as a percentage— so that particular hue has a saturation of 38%.
At this point there was no need to actually DO the math, because PS does that for you. I soon came to realize that the closer together in value the min and max were, the less saturated they were. (if they were only separated by a few points say 128,130,131, we would have a saturation of 2%.)
The further apart the values were, the higher the saturation percentage.
0, 128, 86 is also green, and shows saturation of 100%.
The 'B' element HSB is even easier to determine—it is the maximum reading obtained from the three components of the RGB pixel expressed as a percentage. In the case above, it is 85%
Hue is a little more complicated, but also uses the Min and Max measurements.
My original saturation question stemmed from a need to understand if or how hue, sat, and brightness affected each other. I see now what Guillermo meant when he said these are all independent of each other.
The relationship instead rests in the RGB values.
Raising or lowering the three RGB components of a pixel equally should only impact Brightness (Max) Changing the relationship between the Min or the Max, though (by raising or lowering them independently of each other), will affect the Saturation and Hue of that pixel.
This amounts to a small, unnecessary, but very satisfying peek under the hood, for me. I hope it is accurate.
