Found what I needed
"Fast and accurate model for optimal color computation" by K. Masaoka
https://www.researchgate.net/publication/44673524_Fast_and_accurate_model_for_optimal_color_computation
Thanks for that, Doug.
OBTW, do you know about optprop?
https://www.mathworks.com/matlabcentral/fileexchange/13788-optprop-a-color-properties-toolbox
A really good tool to have in your toolbox.
Jim
See also "A new algorithm for calculating the MacAdam limits for any luminance factor, hue angle and illuminant (https://www.researchgate.net/publication/39435417_A_new_algorithm_for_calculating_the_MacAdam_limits_for_any_luminance_factor_hue_angle_and_illuminant)" by Perales et. al.
Obviously ProPhoto RGB has many colors that are imaginary and so can't be created with lasers or anything else. But what about lowly sRGB and Adobe RGB (1998)? Obviously they are real colors since each of the R, G, and B colors have chromaticity coordinates that are reasonably inside the human gamut.
So, for fun I looked at sRGB and Adobe RGB (1998) to see if they contain colors that are not even theoretically printable.
Good news. sRGB does not. A printer with unlimited and spectrally ideal inks could accurately print all of sRGB. In theory of course. They don't currently come all that close.
Bad news for Adobe RGB (1998). Such a printer can never exist. Specifically, red is a problem. Red RGB values of (240, 0, 0) to (255, 0, 0) are not physically printable. Ever.
This may seem odd since sRGB and Adobe RGB reds have the exact same chromaticies. The reason Adobe fails is that the red luminance at 255 is much higher than sRGB's luminance.
Research for a neon light image reproduction?
Met vriendelijke groet, Ernst
http://www.pigment-print.com/spectralplots/spectrumviz_1.htm
February 2017 update, 700+ inkjet media white spectral plots
displaying prints that appear to be sourcing light, not just reflecting it.
Obviously ProPhoto RGB has many colors that are imaginary and so can't be created with lasers or anything else. But what about lowly sRGB and Adobe RGB (1998)? Obviously they are real colors since each of the R, G, and B colors have chromaticity coordinates that are reasonably inside the human gamut.
An interesting thing is that while ARGB may seem to be within human gamut, that doesn't necessarily mean that it is fully contained within ProPhoto RGB. See the relationship between ARGB and PPRGB below. The area near the saturated unit stimulus blue region of Adobe RGB requires more than unity stimulus from blue ProPhoto RGB primary, i.e., there might be colors that clip for unit stimulus blue primary of ProPhoto RGB but are within the unit stimulus of Adobe RGB.
In a way, yes. I have posted on another thread some of my initial experiments re displaying prints that appear to be sourcing light, not just reflecting it. This is done by illuminating an image with a flood where the unevenness of the reflected light from the flood is corrected. This leaves large portions of the print able to reflect light that appears to have greater luminance than is possible with a purely reflected print.
What this makes possible is displaying prints that have highly luminous sources. For instance light streaming through a window or illuminated signage. The goal is to create a print, that when illuminated, looks somewhat self luminous.
It's also been often noted that an image is expected to look different when viewed on a monitor than when printed absent careful comparison with a proof viewing booth. This is almost entirely because monitors are always viewed in rooms with ambient light, and hence max reflected light in the environs, that is a factor of 2 to 5 times more luminous. The MacAdam limits show that even when luminance of WPs are matched, such as in a viewing booth, monitors still render colors near their primaries that can't be reached by the print. In the case of Adobe RGB, can't be reached by any theoretical printer.
So this was just a side diversion mostly done to improve my intuition while pursuing the goal of super luminous print display. Also, I just find it a lot of fun. I kind of iterate between the intuitive and analytical. They seem to drive each other and it's been my general, productive, approach in many other, unrelated, endeavors.
Bad news for Adobe RGB (1998). Such a printer can never exist. Specifically, red is a problem. Red RGB values of (240, 0, 0) to (255, 0, 0) are not physically printable. Ever.
This may seem odd since sRGB and Adobe RGB reds have the exact same chromaticies. The reason Adobe fails is that the red luminance at 255 is much higher than sRGB's luminance.
So, there aren't any (non-fluorescent) inks that can actually produce those AdobeRGB reds under D50 light. Very interesting. I'm curious what happens when you use Illuminant A (tungsten) instead of D50?
Rounding errors of course. But clipping going from Adobe RGB to ProPhoto? Only in one case and that case involves differences that show up in Absolute Colorimetric and only when using Microsoft's ICM engine. Then and only then, you get the clipping you describe because that engine attempts to preserve the D65 white point of Adobe RGB which it cannot for the reasons you describe. There is not sufficient amplitude to bump up the Z component to the required level demanded by D65.
This, it turns out, was due to an ambiguity caused by a different usage of Relative and Absolute Colorimetry terminology between the CIE and ICC. ICC addressed this about a decade ago by stating that all conversions of matrix colorspaces must use color whitepoint adaptation transforms when changing whitepoints. Even with Absolute Colorimetric Intent.
Adobe's default color engine, ACE, observes this ICC requirement and produces no clipping.