[argyllcms] Re: Beta RGB As a Color Workspace

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Thu, 17 Jul 2014 08:19:18 -0700

On Jul 17, 2014, at 1:59 AM, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote:

> Consider : if you set exposure correctly, then every possible light spectrum
> will generate camera RGB's that are within the range 0..1.

An excellent way to observe this in a way that will make the matter instantly 
intuitively obvious is to photograph a spectrum (such that it doesn't clip) and 
then examine the channels independently. Each will be a continuous ramp (save, 
of course, for any absorption or emission lines). Adjust the levels, and it 
becomes *very* obvious where the IR and UV cutoff filters are. But, that aside, 
you can clearly see that you've got every possible monochromatic color -- the 
very definition of the largest possible gamut -- and each has an RGB value 
associated with it.

Is each value unique? Well, that depends on the filter array design, but the 
Canon 5DIII at least has response curves that at least superficially look an 
awful lot like the S, M, and L curves of the standard observer. I'm sure it's 
not a perfect match, but I'm also quite confident that the camera isn't going 
to be the weak link in the color processing chain.


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