[argyllcms] Re: Calculate RAW importer profiles ?

  • From: Pascal de Bruijn <pmjdebruijn@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Mon, 27 Jul 2015 20:42:42 +0200

On Mon, Jul 27, 2015 at 9:41 AM, Adriaan van Os <gpc@xxxxxxxxxxxx> wrote:

My apologies if this has been discussed again. I searched for the word RAW
in the archives but got quite a large number of hits.

A well known problem is that the output of RAW importers doesn't match the
gamut of the camera JPG output. For example, when I import a Nikon .NEF
with Nikon's proprietary Caputure NX 2 software, the produced TIFF matches
the JPG exactly. When I import the same .NEF with (say) the OS X built-in
CGImageSource RAW importer, the colors don't match. And I assume that
importers like dcraw and ufraw have similar problems.

"Problems" yes... except that it's a problem intentionally created by the
camera vendor, by keeping their color handling secret.

Assigning different profiles to the TIFF imported RAW after import gives
different levels of deviation from the camera JPG. Of course, the problem
is that camera manufacturers keep part of the RAW image data format secret.
And maybe, the RAW importers should do a better job at color management.

This problem is entirely a vendor problem. Most RAW converters color
management is just fine. They just can't know the magic parameters (LUT?)
the vendors use. And even if they did, they might not be able to legally
use them. So you end up in a situation where isn't a single reason why it's
reasonable to expect the same output from a third party RAW converter to be
the same as the camera JPG.

But many cameras do have an option to output both RAW and JPG. And the JPG
does reveal the secret of how the imported RAW should look like (for a
specific set of camera settings). So, why not take the JPG and the RAW
imported TIFFs, compare them and calculate a "raw importer" profile from
both. That profile, when assigned to the RAW imported TIFF would then
represent the best possible color match with the JPG (for a specific set of
camera settings).

I've cobbled this up, with some help from others on this list, in the past.


It's very experimental, so it may or may not work well for you. Please do
read the included README thoroughly before trying.

Pascal de Bruijn

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