[Digikam-users] 16-bit raw color management woes with Canon 30D

[Gerhard Kulzer]

Am Sunday 08 July 2007 schrieb Thorsten Schnebeck:
> Am Sonntag 08 Juli 2007 schrieb Martin Schmettow:
> > Hi Carla,
> >
> > this problem is related to two bugs I recently reported:
> >
> > http://bugs.kde.org/show_bug.cgi?id=146259
> > (Note the comment of Gilles Caulier)
> > http://bugs.kde.org/show_bug.cgi?id=146393
> >
> > In short: There is at the moment no adjustment of 16bit images due to a
> > restriction of dcraw. Instead, 16bit mode preserves the linear curve of
> > the original raw image. In my humble opinion the raw converter should
> > present an easy-to-use function to adjust the curve. If you agree, you
> > might want to vote for the second bug.
> >
> > --Martin.
>
> .. and another hint:
>
> it does not matter what kind of color space you have chosen when you shot
> in raw. The tag oder the differend filename (IMG vs. _MG) are only hints
> for Canons rawfile decoder to create an non raw image in the colorspace you
> select in your cam.
>
> But the raw data itself does not have any interpretations of the embedded
> color space or white balance informations.
>
> Starting with the raw decoding process you transfer 12bit into a
> colorspace. You can not see this depth of color on you screen. Screens have
> only 8 Bit per color so the higher dynamic of 16bit per color is only in
> the data but its not visible.
>
> So the presentation of the 16Bit images in digikam depends on the color
> profiles. For my 20D Bibbles canon1.icc is the one that transfers the
> presentation in a direction that the 16bit image looks like the cams 8bit
> jpeg in terms of color and light but its a little bit darker.
>
> As mentioned there is some kind of auto-adjustment missing in digikam to
> get the same visual interpretation like ufraw - but digikam has a different
> workflow compared to ufraw.
>
> HTH
>
>   Thorsten

I use a 30D too and agree mostly with Thorsten. 
If you want a lightness-corrected image, use the 20D profile from LZ.2.0

It's not so interesting to reproduce the JPG conversion, therefore I often use 
various 6112 profiles. They are different between each other, for example the 
ntl has much more vibrancy than the others, but can only see the difference 
when you have the lightness corrected. So I have a setting saved that I can 
recall for lightness correction.

Gerhard
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