[argyllcms] Re: Quality of camera profile - colour banding

Klaus Karcher wrote:
> edmund ronald wrote:
>> In my experience, current dSLRs are pretty well linearized in Raw mode.
>> Obtaining decent color from them is a matter of locating the primaries.
>> The raw2xyz transform can be considered to be a matrix.
>> The problem resolves into a one line Matlab or Ocatve program.
>> Whether you want to deal with flare, or other secondary phenomena, is
>> a different issue.
>
> Is it usual to get primaries way beyond the spectral locus or even
> with negative components (e.g. like those in Milan's profiles) with
> current cameras? 

It depends on the method being used. There are several methods proposed
in the literature for deriving the 3x3 matrix, which claim to work
better than a simple minimization of an error metric in a least squares
sense, for a given a calibration target. Some of them seem to make use
of additional constraints like exact mapping of white, positivity of the
captured spectra, or particular assumptions about the correlation of the
captured spectra (e.g. smoothness of the spectra), etc. I haven't yet
looked into these subjects in detail though.

Regards,
Gerhard

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