[Digikam-users] Jpeg export changes image

[Guillaume Castagnino]

Le vendredi 19 octobre 2007, Arnd Baecker a écrit :
> Hi Bill,
>
> I think that your question is related to this wish,
>   http://bugs.kde.org/show_bug.cgi?id=142055
> but I might be wrong.
>
> Guillaume, maybe you can explain things? ;-)

Hi,

No I don't think help here.
The problem encountered by Bill here is probably the lack of color 
management profile that impacts the color rendering far more than (in 
fact more acuratlly) setting a right color balance or an auto exposure.

Currently, the raw converter in 8bits will do auto-exposure of the raw, 
so it's not problematic, the "lights" will be correct
My patch will help setting more preciselly the raw white balance.

But IMHO, the problem that bill have here is some wrong color rendering 
more than exposure or white balance. A color managed view will change 
in a non-linear way the color balance of the picture.
Look here for example, and especially the pictures on the right : 
http://ufraw.sourceforge.net/Colors.html
Some colors have a big change (look especially at the purple balloon, 
the pink shirt, and the yellow trousers), this is what color management 
do : some color are renforced, some other are attenuated, and so 
picture saturation can greatly change, in order to better fit the real 
colors (profile depending on the camera used).

For the story : I generally get the same pale result without using any 
color profile with my Canon 400D. Using the right color profile solves 
those color fidelity problem :)

Regards,
Guillaume

-- 
Guillaume Castagnino
    guilc at laposte.net / casta at xwing.info
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