[Digikam-users] Re: Color Management Jeopardy

[Gilles Caulier]

Elle,

In my TODO list, i must improve this CM panel in RAW Import tool to be
able to use digiKam CM settings from config dialog. The idea is to
provide the list of profile set and available in this settings to
simplifly configuration.

Gilles Caulier

2011/3/16 Elle Stone <l.elle.stone at gmail.com>:
> 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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