[Digikam-users] Dark 16 bit RAW decoding

[Gerhard Kulzer]

Am Friday 25 January 2008 schrieb Paul Waldo:
> I stumbled across a discussion of dark RAW conversions in the FAQ. 
> Apparently Digikam cannot use the manufacturer-supplied camera profile, yet
> UFRaw can. This puzzles me, since they both are just front ends to dcraw...
>
> My manufacturer-supplied camera profile works great in UFRaw, with gamma
> set to 0.45.  When I use the same profile with Digikam, I get a dark image.
>
> So, I tried to take the FAQ's advice.  I created a profile by photographing
> an IT8 target and using lprof to create a profile.  When I use this new
> profile for Digikam RAW conversion, I get an image that is even darker than
> when I used the manufacturer-supplied camera profile! :-O
>
> I'm sure that someone out there has gotten 16-bit decoding of Canon raw
> images to work well.  Any hints?  Thanks in advance!
>
> Paul

As I understand it, Canon profiles that come with the camera lack tone mapping 
and gamma correction parameters. digiKam does not touch these properties 
during raw conversion, but Ufraw does. They have a whole lot of code to 
supplement dcraw in the conversion process. One day dcraw will hopefully do 
it as it does it already for 8 bit, or we'll integrate the ufraw code.

On the other hand Bibblepro and selfmade lprof profiles work well with digiKam 
in my experience since they have tone mapping included, images come out 
normally bright.

Gerhard
> On Wednesday 16 January 2008 10:30:47 am Paul Waldo wrote:
> > Thanks for the reply, Jakob.  Comments below...
> >
> > Jakob Østergaard Hegelund wrote:
> > > On Wednesday 16 January 2008, Paul Waldo wrote:
> > >> Hi all,
> > >>
> > >> When I try to edit a RAW image, it is very dark.  Yes, I did RTFM; I
> > >> have color management enabled :-)
> > >>
> > >> I'm running digikam 0.9.2-final on KDE 3.5.8
> > >> Here are my digikam settings:
> > >>
> > >> Color Management
> > >> ------------------------------
> > >> Enable Color Management: on
> > >> Launch Color Management plugin with RAW files: on
> > >> Use color managed view: on
> > >> Color profiles selected for Monitor, Workspace (Adobe RGB), Input,
> > >> Soft Proof
> > >> Black point compensation: off
> > >> Rendering Intent: perceptual
> > >
> > > My guess would be that you're using the wrong profile.
> > >
> > > I had a *lot* of problems with this, but with the right profile for the
> > > camera (and none for the monitor as it's sort-of close to sRGB which I
> > > also use as workspace), everything works.
> >
> > I'm using the same profiles that work great in UFRaw.  That got me to
> > thinking about the differences.  When I convert using my profile in
> > UFRaw, I set the gamma to 0.45 and linearity to 0.02.  I see no way to
> > do this in Digikam...
> >
> > >> RAW Decoding
> > >> --------------------------
> > >> 16 bit color depth: on
> > >> Interpolate RGB as four colors: off
> > >> Use camera white balance: on
> > >> Automatic color balance: on
> > >>
> > >> Thanks for any insights!
> > >>
> > >>
> > >> Paul
> > >>
> > >> PS
> > >> Is there any way to select a specific color balance when converting
> > >> RAW?  Camera WB works most of the time, but sometimes I need a manual
> > >> WB, such as when photographing with a grey card.
> > >
> > > The RAW converter uses the cammera supplied WB, which means, if you set
> > > the custom WB on the camera when you use grey card (select the grey
> > > card image for custom WB before shooting the real photos), the correct
> > > WB will be applied automatically during conversion.
> > >
> > > At least this is how it works in 0.9.2 with my EOS 350D.
> > >
> > > For actual WB adjustments later on, use the WB adjust tool in the
> > > editor.
> >
> > Ah, OK.  I had not seen that before.  FWIW, I tried setting gamma here,
> > but it had no effect.  The only thing I could do was the the EV
> > Compensation way up (3 EV).  In order to do a manual WB with the picker,
> > I had to guess where to click because the image was so dark!
>
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