[argyllcms] Re: Extract L*a*b, XYZ values from a target image using scanin

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 12 Feb 2013 12:00:51 +1100

David Irisarri wrote:

> 1. Take a picture of the Color Checker chart with the camera and
> export it in TIFF AdobeRGB (biggest color gamut of the camera, no
> color patches out of gamut)

> 2. Extract color values of these patches and create a CGATS file
> according to these values. I want these values in L*a*b and XYZ.

> 3. Process the same image with dcraw (no color management raw color)
> and create a color matrix using the reference previously created.

Hi,

You haven't really explained what you are trying to do. If you are
trying to create a profile for the dcraw output that is colorimetricaly
accurate, then you are on the wrong track, since you aren't basing
it on any measured CIE values. If your aim is to reproduce the
"look" of the in camera processing using dcraw, then I guess this approach
may (sort of) work. [The assumption would be that you feed the output
of dcraw though the profile and then through AdobeRGB.] The limitation is
that such in-camera processing may not be perfectly captured by a profile
(particularly a matrix profile), and certainly can't capture dynamic white
point selection, nor automatic exposure adjustments.

Graeme Gill.

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