[argyllcms] Re: sRGB/AdobeRGB98 vs Lab (was Verifying profile quality...)

Milton Taylor wrote:

Question for you: what energy levels are required to generate the colors that are at the extremes of this chart? Are they dangerous? If so, then I'm not sure this chart is all that useful...it would need to be bounded by a safe/reasonable energy limiting shape. 

The energy is approximately 1/CMF value, and since CMF's
go to zero out of visible wavelengths, the energy has to
go to infinity. I stopped at 380nm and at which the Y sensitivity
is 0.000039097450, so on the order of 26000 times the light
level at our most sensitive wavelength (555nm). At 380nm,
this may give you a really good sun tan.

Most color work simply assumes that it all looks
the same, as long as it's photopic, and doesn't assume a maximum.
Only some color appearance models (ie. Hunts model) and safety
folks worry about absolute light levels once it's out of
the scotopic region.

On the other hand if it's all safe...then does it not answer the original question about what colors the eye can see? (Also, how do you know this is what the eye can see? i.e. what is the basis behind this shape?) 

It's all in the Colorimetry theory. Basically a monochromic source
must be able to generate the most difference in cone responses, hence
most saturated colors (or two sources along the purple boundary).

Now that's a very interesting suggestion. Suppose you leave the panel's backlight at 250 cd/m2, why could we not get the profiler to take advantage of this fact, still scaling white to 125, but allowing the other colors that the eye is less sensitive to, to go brighter, to the max of 250? Or am I missing something here? 

It should be practical to create a LUT based profile that does this sort
of thing. The main problem is that the windowing system will sabotage
the effort. It will send direct RGB values to the screen via the RAMDAC
tables (for window decoration) making sure you're adapted to the 250 cd/m2
white point. You'd need a full screen application that used the profile to
be able to exploit this approach.
(I'm not sure any of the OS/windowing systems actually properly send
 everything through a display profile, nor is there a way of stopping
 some applications bypassing such a default behaviour.)

Graeme Gill.

Other related posts: