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

[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