[argyllcms] Re: Custom Illuminant

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 8 Jul 2014 10:58:10 -0700

On Jul 8, 2014, at 10:01 AM, Roger Breton <graxx@xxxxxxxxxxxx> wrote:

> My very humble experience is leading me to believe that there are very few
> instances of saturated colors in photographs or every day pictorials?

Saturated colors are very uncommon. Most colorants have spectral profiles 
similar to those of the paints artists and home painters use. Yellows, oranges, 
and reds all reflect nothing shorter than a certain wavelength and have a steep 
transition to being highly reflective (and basically flat) at some point; where 
that point is is what determines their color, and how sharp the transition is 
determines their saturation. Greens and blues and violets have a single 
spectral peak that doesn't tend to be all that bright. The wavelength of the 
peak determines hue again, and the slope of the peak determines saturation. 
Then, of course, there're all the mixtures, including many metameric matches 
with much more complex spectra.

To get truly saturated colors you generally need quantum mechanics: diffraction 
gratings and variations on that theme (including butterfly wings), or lasers. 
(There are other sources, but none common).

But, even if you're photographing something iridescent or a laser light show or 
the like...how are you going to output those saturated colors?

Your monitor isn't going to come close. Your printer doesn't stand a chance.

Unless you're doing some sort of empirical analysis, the fact that you've got a 
digital file with numbers representing those colors really doesn't do you much 
good.

There might be some large gamut monitors or printers that are finally pushing 
the boundaries of BetaRGB. It's probably a good time to start thinking about an 
update (GammaRGB?) with a gamut expanded enough to accommodate the next couple 
generations of devices. But, unless you're already outputting to something with 
a gamut larger than BetaRGB, you're basically not going to find a better 
compromise than what BetaRGB already represents.

b&

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