So... how do I use this?

If I go to that website link I only get one value for n and k, I can't find anything that tell me the RGB parts,

also if I compare the presets values with the info in that website, they look different.

Any ideas?

Thanks.

The RGB wavelength values are taken as the median of their ranges typically. If you look up red on wikipedia for example, its range is 620-740, so the 650 value used in the map is an approximation of its average. You would then find that number for each color, and input it into the wavelength box on the refractive index page.

For example (the copper values), inputting the R value of .65 gives you an n=.27105 and k=3.6092, hence the .271 and 3.609 in the map. Inputting the same RGB wavelength values under a different material from the index pull down will give you the corresponding n and k values for that material (ie: for aluminum, R value of .65, n=1.3424, k=7.4737, which aligns with the values on the fresnel map)

These are estimated numbers of course, not exact values.