[argyllcms] Re: camera profiling with newest version of Argyll

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 28 Aug 2015 11:32:58 +1000

Ben Goren wrote:

Hi Ben,

The first patch has L* a* b* = 96.709 1.8667 -13.059, which is decidedly
bluish

I'm not sure where you get that value from - spec2cie says it is
96.694984 -0.854171 0.157998.

(Note that there is a bug in "spec2cie -n" - you can get wrong values out of
it. I'll
fix this in V1.8.1).

I just plotted the spectrum for that patch. It really does look like it's
full of FWA.

But this chart was measured using a ColorMunki - the ColorMunki uses a white
LED,
so it has no UV illumination, and won't trigger FWA, even if it were present.

Comparing the spectrum to a reference I have of the ColorCheckerSG measured
using the
Spectrolino, the reflectances look very similar from 420-730 nm, but the
ColorMunki
values below 420 are "guestimated", since the illuminant drops off there, and
the diffraction grating looses efficiency.

The A1 white patch D50 L*a*b* comes out at 97.222621 -0.954457 0.777881
for the Spectrolino, and 96.694984 -0.854171 0.157998 for the Munki.

So I think you are on the wrong track.

Graeme Gill.

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