16-bit raw color management woes with Canon 30D

[Carla Schroder]

Raw color input profiles are driving me batty! In fact none of the profile
settings do anything. I have a Canon EOS 30D set to AdobeRGB. I have all of
the 6112 input profiles, which came with the camera, and are also available
here:
http://digikam3rdparty.free.fr/ICCPROFILES/CameraProfiles/CANON/Canon 30D/

This page tells which input profiles to match to the correct camera model:
http://www.maashoek.nl/color_profiles.html

But none of them work in Digikam. They make zero difference- 16-bit RAW images
are very dark, as they are supposed to be with no color management, and
applying the 6112 profiles does not change anything. So I tried some of the
files from
http://digikam3rdparty.free.fr/ICCPROFILES/CameraProfiles/LZ.2.0/

and these actually lighten the images a little bit, but they're still very
dark. There aren't any specifically for the 30D, and I haven't found any
elsewhere.

Has anyone been successful in using the 6112 input profiles? I love Digikam-
it's a great application that outperforms the Canon bundled software, and I
hate using Windows anyway. Is there some other workaround? Should I just cuss
Canon and take small comfort from that? :)

Kubuntu Feisty
Digikam version 0.9.1
RAW decoding settings:
16 bits
Use camera white balance
Bilinear interpolation

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[Carla Schroder]

On Friday 06 July 2007 14:18:57 Carla Schroder wrote:
> Raw color input profiles are driving me batty! In fact none of the profile
> settings do anything.

Forgot to mention that by setting it to 8-bit RAW, all the color profiles
work, including the 6112 files. Shouldn't it work the same at 16-bit?

thanks much!

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Carla Schroder
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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.

Carla Schroder schrieb:
> On Friday 06 July 2007 14:18:57 Carla Schroder wrote:
>> Raw color input profiles are driving me batty! In fact none of the profile
>> settings do anything.
>
> Forgot to mention that by setting it to 8-bit RAW, all the color profiles
> work, including the 6112 files. Shouldn't it work the same at 16-bit?
>
> thanks much!
>


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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
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[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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[Carla Schroder]

On Sunday 08 July 2007 08:56:57 Martin Schmettow wrote:

> 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.

Thanks, that's some useful information. It's confusing because the various RAW
convertors work differently, and most of them do some sort of automatic
lightness or gamma correction even in 16-bit mode. I'm OK with starting with
a completely uncorrected image if I really really want ultimate control. The
confusing bit was all the discussion I've read about using input profiles in
Digikam doesn't make it clear that these aren't really for 16-bit RAW
conversions.

--
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Carla Schroder
Linux geek and random computer tamer
check out my Linux Cookbook!
http://www.oreilly.com/catalog/linuxckbk/
best book for sysadmins and power users
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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