[argyllcms] Re: Metameric Mismatch
- From: Gerhard Fuernkranz <nospam456@xxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Sun, 12 Oct 2014 23:20:04 +0200
Am 12.10.2014 um 18:32 schrieb Ben Goren:
Gerhard, what about the reverse? If you have a chart with both reference values
and profiled RGB / XYZ values from a photograph, how practical is it to
estimate the spectrum of the illuminant used for the photograph? Assume, of
course, a chart with lots of different reflective spectra, maybe even some
shifty metamers.
Hi Ben,if you know the reflectance spectra of the patches and the corresponding
XYZ numbers under an unknown light source spectrum, then IMO you still need
samples spanning the full dimensionality of spectral space in order to
reconstruct the spectrum of this light source. And since one can hardly provide
samples with rank of 10 or more in practice, I'd say this reconstruction
problem is eventually ill-conditioned either.[ At least on the fly no other
method comes into my mind than solving the inverse problem - I'd need to think
about it in more detail... ]
Regards,
Gerhard
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