Yes I agree that there is an arbitrariness to this, but it must be possible to settle on some safe energy limits (that correspond to the typical energy for 'white' on a good LCD (250 cd/m2 ?) regardless of the color?I can see it would be useful perhaps to have two shapes then, i.e keep them separate. One for 'safe emissive conditions', and one for typical reflective conditions, assuming D50 white point with optimal lighting, perhaps as you might find in a gallery [and not the average home loungeroom].
For some purposes, yes. The emissive one is still pretty arbitrary however (how much light to you assume it can generate at an individual wavelength, compared to the white point ?), and even the reflective one has a degree of arbitrariness, in the choice of illuminant.
I still see value in having them as two separate shapes for gamut comparison purposes, but there's nothing to stop you - if it was seen as useful - from then taking the union of the two, representing the gamut of human vision for all practical purposes. Mathematically that might well have discontinuties in it, but that's probably a lot easier than trying to model both gamuts in one set of transforms?Having two "visible gamuts" defeats the original purpose I think, since it was to compare different types of output devices.
Yes that's true, but I don't see a problem with that. If you do this with an LCD, and it's set to maximum backlight brightness you're doing this anyway since any adjustment in the monitor's white balance color temp is just ultimately fiddling with the input values, so one might as well let the profile do it all.An associated factor (which is largely being overlooked in all this I think), is that the color gamut of an emissive device can be manipulated by the choice of white point.
Using display calibration to set maximum brightness defeats this idea, and the normal ICC way of storing relative colorimetric information also works against it, but if the maximum brightness was set in the profile (and this might be something as simple as setting a white point below the level of the maximum output, depending on how the profile was subsequently used), the effective gamut of a display can be boosted considerably in the area of bright saturated colors. I'm not sure this would help much in making a display encompass more of a printing gamut (since printers tend to be large in the darker saturated colors area), but it could help (particularly when modern LCD monitors have brightness to burn.)
..Milton
