[Digikam-users] Printers with full Color Management

[Milan Knížek]

Marcel Wiesweg píše v Út 01. 09. 2009 v 19:49 +0200:
> > camera icc profile prepared for Adobe Lightroom will most probably
> > provide different colours in UFRaw. Not saying worse or better, but
> > different. But yet - if you do not have anything better and are happy
> > with the result, do not worry.
> 
> The part about the printer is clear to me, but where is the difference for RAW 
> files? I see there can be differences in RAW development - demosaicing 
> algorithms etc. - but once you have your colors in uncalibrated color space, 
> applying the color conversion using the input color profile should be the 
> same?
I cannot provide much technical details at this area, just a laic
understanding of the information available on ufraw and argyllcms
mailing lists...

AFAIK, the thing is that not all converters apply the same steps in the
same order and that some of the steps are variables affecting the raw
and rgb data. Some of the settings can be set by the user, some may be
hidden (and proprietary).

E.g. UFRaw applies white balance, highlight-reconstruction, wavelet
de-noising, raw curve adjustment, gamma and linearity before assignment
of the camera profile.

Next problem is that the camera sensor does not react fully linearly to
the light - hence an icc profile prepared for a particular
white-balance/raw curve/etc. and used for another
white-balance/curve/etc may provide different result even in the same
raw converter.

If my understanding is wrong, I would be more then happy to know other
opinions.

P.S.2 The difference is quite obvious when using Canon's Digital Photo
Professional and UFRaw. There are methods how to find out, which ICC
profiles are used by DPP in MS Windows. However, people were usually not
able to get the same output from UFRaw with those profiles. (I tried
myself and skipped this approach - the Adobe Matrices in dcraw based
converters provide better results).

regards,

Milan Knizek
knizek (dot) confy (at) volny (dot) cz
http://www.milan-knizek.net - About linux and photography (Czech
language only)