[argyllcms] Re: White Point

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 9 Nov 2015 16:35:09 -0700

On Nov 9, 2015, at 3:59 PM, Thomas Mansencal <thomas.mansencal@xxxxxxxxx> wrote:

And I'll bet another cup of coffee that their method could be adapted to
determining an optimal set of primaries...and another cup (not on the same
day!) that the optimal primaries are going to be within shouting distance of
the 450, 550, and 600 nm peaks of the standard observer, with red and its
funky double hump being the farthest from the peak and blue being next
farthest (to compensate for the red).

This is somehow planned indeed, we need to find time for it and implies some
currently being done spectral API refactoring on our end but the document
will be re-visited for sure.

Good to know! I don't want to speak for Graeme, but I know I'd appreciate if
you tipped off this list when you've done so, and I'm pretty sure Graeme at
least wouldn't mind.

And...something else related that I think would be worthwhile that I'm not
right now in a position to do but would likely be right up your alley...would
be a synthetic re-creation of Pointer's Gamut. I'd start with something like
what Mika, Hannu, Pasi, and Markku have done here:

http://www2.uef.fi/sv/spectral/smooth-spectra

and compute the gamut at least using all the standard illuminants (including
arbitrary D- and A-series). Yet another cup of coffee says the result is a lot
smoother than what Pointer came up with...and that there's likely some
relatively simple abstract method of deriving it rather than by brute-forcing
the problem. Maybe it's simply an uniform shrinkage of the total gamut, with
the degree of shrinkage related to how much spikiness there is in the
reflective spectra?

I would like to see more movement toward spectral rendering and related but
there are still some challenges. I speak a little bit about that in the
conclusion of that post:
http://colour-science.org/blog_about_rendering_engines_colourspaces_agnosticism.php

You're approaching the subject from the perspective of synthetic rendering
whilst most here are coming at it from camera and scanner input and display and
printer output -- but that's good, because you have at least the theoretical
ability to work directly with multi-spectral color from the get-go whereas it
takes some really intensive and non-standard capture setups and even more
non-standard workflows to do multi-spectral color from my end of the field.

I've got a spectral profiling workflow figured out with some proof-of-concept
demonstrations I'm extremely happy with, but it's only the profile creation
process that's multi-spectral. I haven't delved into the working space end of
things the way you have...and your source material is simpler and more
idealized than mine, which means you might not be as distracted by certain
irrelevancies as I might be....

Cheers,

b&

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