Ok, so the color seen depends on illuminant, which can be shown on the diagram. Each time the illuminant changes, the coordinates of the color shift. Is there a mathematical way of predicting exactly where the coordinates will shift? I say there has to be. Now, what is the formula? Does anyone know? Unfortunately, my knowledge of calculus is ridiculously small, so I can't really derive it on my own Please Register or Log in to view the hidden image! If anyone is interested but doesn't have enough info on the CIE chromaticity diagram, ask and I'll post whatever I was told in class. :m:
I'll assume that you are talking about the coordinates on one of those x-y diagrams. My initial response will be, "I doubt it," but I don't know exactly how those diagrams relate to the spectrum. I am assuming that you mean, "given only the reflected spectrum of sample A (R<sub>A1</sub>) under illuminant 1, illuminant 1 (I<sub>1</sub>), and illuminant 2 (I<sub>2</sub>): is there a way to predict the reflected spectrum of sample A under illuminant 2 (R<sub>A2</sub>)?" For example, consider the extreme case of illuminants given by: I<sub>1</sub> = δ(λ - 650 nm) (pure red). I<sub>2</sub> = δ(λ - 450 nm) (pure blue). If R<sub>A1</sub> = a δ(λ - 650 nm), that tells you nothing about R<sub>A2</sub>, because regardless of what you assign for R<sub>A2</sub>, it will not contradict the given spectrum for R<sub>A1</sub>. This, of course assumes a linear response (i.e. no flourescence).
Whitewolf, It has been a few years since I was up on that diagram and when I was it was for color television. One of the problems if this is what you are looking at is that the triad color system in TV doesn't match actual color mixing. That is to say the phosphors are not in one to one correspondance with theoretical mixing. To see a color they actual mix in different ratios than you would in paint or dye to see the same color. I would have to agree that there probably isn't a formula to get from one color to another. There are to many variables. TV produces a tristimulus signal that is added to the monochrome signal to produce color by exciting the color triad. The eye is more sensitive to red than blue and I forget the offset from the theoretical color triangle to a chromacity diagram but I seem to remember it is almost twice as much blue. A book on color TV should give the ratios.
