[argyllcms] Re: ProPhoto to sRGB device link problem

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Fri, 02 Oct 2009 10:28:34 +1000

Ben Goren wrote:

Hmmm...Graeme, would that make sense for an addition to Argyll? Maybe something like an option to tiffgamut that creates a new working space profile just for that image? One could then (for example) re-process the RAW file and do a gamut-mapped conversion directly to the new space. Tedious to do by hand, but probably not that bad as part of a script that's in turn part of a batch process.

It's certainly possible, but I'm not sure that it's really
tackling the right problem. The are really two distinct situations,
depending on whether imagery has been rendered into a restrictive
gamut or not.

If the imagery has been fitted into a restricted device
space (ie. it's been rendered into that space, making the best use of it),
then the colorspace gamut is a good representation of the gamut of the
imagery, and can be used to guide re-rendering to some other output media.

If the imagery is input referred (ie. it encodes real world
colors) or if it has been rendered into an output colorspace
that is noticeably larger than that of the image, then the encoding
colorspace doesn't represent the imagery gamut, and you'll get
bad results if you use it as if it does. To get good results
you have to determine a gamut that does represent the imagery.

Argyll can support this sort of workflow using tiffgamut.

[ Note that ProPhoto is actually the basis of the RIMM and ROMM
 standards for input referred and output referred encoding.
 See <http://www.colour.org/tc8-05/Docs/colorspace/PICS2000_RIMM-ROMM.pdf> ]

Graeme Gill.

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