[Digikam-users] Re: Color Management Jeopardy

[David Vincent-Jones]

With so many persons using so few (relatively) camera models I am really
surprised that there is not a wealth of camera profile data sitting out
there for common use.

Canon, unfortunately, now bury their information in a welter of
propitiatory files, it almost appears that this manufacturer is trying
to force the world into its software. Shame!

Maybe it needs the open-source community to assemble and disseminate
reliable information.

David

On Wed, 2011-03-16 at 12:47 -0400, Elle Stone wrote:
> On 3/15/11, Graham Dicker <graham.dicker at antecor.com> wrote:
> > First question that I have is how do I deal with the
> > raw images out of my Pentax K200D? There is no embedded profile in the raw
> > files and I cannot find one for this camera anywhere on the internet. On the
> > CD that came with the camera there are icc files for sRGB and AdobeRGB but I
> > don't know if these have any bearing on the processing of PEF/DNG files.
> >
> 
> Hi Graham,
> 
> I haven't finished exploring the digiKam raw converter. But there are
> three choices for the camera profile: "None", "Embedded", and
> "Custom".
> 
> "None":
> I assume that "None" means use the default camera matrix in the dcraw
> code. That's the only logical conclusion, and the output using "None"
> is identical with UFRaw output, after adjusting for exposure. The only
> thing is, if you use any "Workspace" color space other than sRGB,
> digiKam doesn't seem to handle the Tone Response Curve ("gamma")
> correctly. (TRCs aren't always a true gamma curve; sRGB doesn't have a
> true gamma TRC; digiKam seems hard-coded to use the default dcraw TRC,
> which may or may not be exactly the same as sRGB - I'm too lazy to
> track down the answer - but the default dcraw TRC is most definitely
> not a true gamma curve.)
> 
> The digiKam raw converter uses libraw, which gets its camera matrices
> from the dcraw c-code. dcraw c-code does have a camera matrix for the
> K200D:
> 
>  { "PENTAX K200D", 0, 0,
> 	{ 9186,-2678,-907,-8693,16517,2260,-1129,1094,8524 } }
> 
> The matrix above is what is used to convert your interpolated raw file
> from the "raw" color to a working space.
> 
> "Embedded":
> "Embedded" is an option from the dcraw code that only applies to a few
> cameras. Quoting from the dcraw documentation
> (http://www.cybercom.net/~dcoffin/dcraw/dcraw.1.html):
> 
> "+M or -M Use (or don't use) any color matrix from the camera
> metadata. The default is +M if -w is set, -M otherwise. This option
> only affects Olympus, Leaf, and Phase One cameras."
> 
> 
> "Custom":
> "Custom" requires that you have your own custom camera profile, for
> which you'd need a target, the least expensive of which is made by
> Wolf Faust (http://www.colorreference.de/targets/index.html - you'd
> need to purchase the C1 target).
> 
> So I'm not sure how to respond to your question regarding the K200D -
> is the problem that you aren't happy with the colors you are getting?
> Or you are not sure about the digiKam settings to use? Or something
> else altogether? (Feel free to send a private email if the problem
> isn't really digiKam-related.)
> 
> Martin is correct when he says that the manufacturer's camera profile,
> if you could even find one, isn't likely to work very well when using
> any software other than the manufacturer's own proprietary raw
> rendering software.
> 
> Many people (including myself) do choose to create their own custom
> camera profile because they are not happy with the colors coming from
> the default dcraw camera matrix. My own custom camera profiles are
> simple, general purpose matrix profiles, just like the ones that dcraw
> uses, only the colors are nicer. A lot of people who own Nikon and
> Canon cameras feel that the default dng matrices produce anemic colors
> for these cameras.
> 
> Elle
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