[argyllcms] Re: Calculate RAW importer profiles ?

  • From: Adriaan van Os <gpc@xxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 27 Jul 2015 14:35:40 +0200

Graeme Gill wrote:

Adriaan van Os wrote:

You could try using a real photographic test chart like the ColorCheckerSG,
but this has it challenges, and would limit the gamut and detail possible
in characterizing the two RAW processors.

My thinking is, not to use a test chart, but the existing photo library that a photograher has on his hard-disk and let statistics do its work to compensate for lack of full test-gamut in single photos. So, we have a JPG with a known profile and we can convert the JPG RGB pixel values to XYZ. And we have a raw-converter produced TIFF with different colors. So, the task is to calculate the color transform that would produce the same XYZ vales for the TIFF as in the JPG. That color transform then constitutes the Profile to be assigned to the TIFF after the raw converter has done its work. This is repeated over many photos and a statistical average (mean or median) is calculated. The standard deviation would be a meaningful value too.

How would an algorithm that does this, roughly look like, apart from the statistics, so for a single photo combination ? I assume the algorithm is much like what color matching systems do, or with reverse math.


Adriaan van Os

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