[argyllcms] Re: camera calibration targets
- From: Graeme Gill <graeme@xxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 12 Aug 2011 09:00:45 +1000
Marco Noldin wrote:
> With "-q u -a m -u" I obtain a good result (dE00max = 2) but ColorSync
> reports
> the blue and green primary in red, why (see attachment)?
Because it objects to the -ve values, because the ICC spec.
forbids them. You can prevent these by using the -R flag,
but the profile will probably be a poorer fit to your camera.
Most software will cope with these -ve values (they are just
the transform matrix values).
[The ICC is in error in not allowing -ve values, since
such values are perfectly valid in matching the response
of input devices, even though they are much less likely in
matching the response of output devices that would have to
have primary colorants with such XYZ values. ]
Graeme Gill.
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