Milton Taylor wrote:
Mmm...that would be really useful...what is the obstacle to defining the curves of the visual gamut...are they simply not known, or do they vary too much from one person to the next?
The obstacle I've run into, is that to get a usable gamut, you have to choose some rule on the energy in the possible light being converted to color.
For instance, if you compute the gamut of the spectrum locus for all XYZ numbers with Y values up to 100, you get quite extreme colors in the purple region (Something like a* 1172, b* = -984 if you stop at 380nm), and this corresponds to very high energy levels being used at wavelengths in which the eye is quite insensitive. In a technical sense, this is the true visual gamut, but in practical terms, it's not very meaningful to compare this with output devices. An output device that attempted to cover this gamut would have to put out extremely high light levels at extreme wavelengths, something that would probably be quite dangerous, and highly impractical.
You can choose other energy rules, and they would probably give other results. For instance, one could assume a reflective environment illuminated with a particular white spectrum (ie. completely flat, or daylight of some kind), and then compute the gamut of every possible spectrum that could be produced by subtracting from the illuminant. But this gamut would exclude large areas that could be produces by quite practical (and safe) emissive devices.
Other people have (perhaps) tackled this quandary. I'm not sure what conclusion they came to.
Graeme Gill.
