[argyllcms] Re: Tuning ACR Calibrator script w/ ColorChecker and illuminant spectrum readings

  • From: Niccolò Belli <darkbasic4@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 09 Nov 2010 03:16:28 +0100

I'm sorry, playing with color conversions until late does bad jokes
sometimes :)
--cat is obviously not needed, because argyll already knows the
reference white (illuminant.sp) and the PCS white (D50 for prophoto.icm).

So the command will be:
spec2cie -i my_custom_[A|D50|D65]_illuminant.sp -o 1931_2 -n --rgb
Prophoto.icm colorchecker.ti3 copypasteme.ti3

Anyway, having an option to save chromatic adapted XYZ/Lab values can
still be useful for other purposes.


Il 09/11/2010 01:04, Niccolò Belli ha scritto:
> Hi, I'm writing because it's actually quite hard to do it with Argyll
> and I have a wishlist for spec2cie.
> Tindemans ACR calibrator script
> (http://www.21stcenturyshoebox.com/downloads/ACR-Calibrator-L-v31.jsx)
> stores the ColorChecker reference values in ProphotoRGB. It stores
> values for three illuminants: A, D50, D65.
> If you convert spectral readings w/ spec2cie
> spec2cie -i illuminant.sp -o 1931_2 -n measurement.ti3 converted.ti3
> then you have to do CAT from the source illuminant (illuminant.sp) to
> the destination illuminants (A, D50, D65) and also convert the XYZ/Lab
> values to ProphotoRGB.
> This is a *VERY* long work to do manually with the help of the Bruce
> calculator (http://www.brucelindbloom.com/). Also, the Bruce calculator
> only supports few illuminants, so you have to implement your own CAT
> into an excel sheet if you want to use your custom illuminant.
> So I suggest to add two more parameters to spec2cie: --cat and --rgb
> The first will do chromatic adaptation transform to the given
> illuminant, the second will convert the chromatic adapted values to the
> selected profile.
> So the command will be:
> spec2cie -i myilluminant.sp -o 1931_2 -n --cat [A|D50|D65] --rgb
> Prophoto.icm colorchecker.ti3 copypasteme.ti3
> Cheers,
> Darkbasic

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