On 2010 Jun 6, at 1:51 PM, Elle Stone wrote: > But really even ProPhoto isn't big enough for all images. It's even worse than that, I'm afraid. The spectrum locus lies at least partially outside both Lab and XYZ color spaces. That is, there are huge swaths of spectrally-pure colors that no color space in use today can encode without clipping. The good news is that these colors are rarely encountered outside of lasers or tunable diffraction gratings. (And prisms.) The better news is that few input devices can capture these colors -- and no output device can even come vaguely close to reproducing them. Some time back this whole point was driven home to me in a pretty emphatic manner when I tried to create a digital rainbow. I created a .ti3 file that was all zeros except for a single frequency at 100, and used fakeread to convert that to Lab colors. Much beyond the far red and violet portions of the spectrum, Argyll began reporting Lab values well beyond 100 L* and 127 a* and b*. So, after some experimentation, I kept the single peak at 100 but added values of 50 on either side. It brought the Lab values closer to within range, but still waaaay out. It eventually took a very wide-band bell curve to get something that would fit in Lab space -- and that, of course, was still waaaaay outside any other color space. Attached is the end result in sRGB. (I think I just used Photoshop to convert from Lab to sRGB, so it's decidedly not the best possible representation, but not all *that* bad.) Even aside from the banding from the very low resolution, it's pretty obviously not what one sees in a sparkling crystal. Yet it's probably about as close as you'll ever see on anything even vaguely resembling an LCD display, picture tube, or any similar device. A wide-gamut monitor would obviously do better, but even those are so far from being capable of creating spectrally-pure colors it's not even funny. And printers? Don't make me laugh. When the pixels in our displays are made not of three primaries (or even twice that number), but are made from tunable diffraction gratings (or something along those lines), then it'll be time to worry about the limits of modern color spaces. Until then, it's just an exercise in futility. For printing, barring some truly radically revolutionary advances in chemistry and physics, it'll never even pretend to be a problem. Cheers, b&