[Digikam-users] converting Pentax RAW problem

[Gilles Caulier]

2007/6/8, Martin Schmettow <schmettow at web.de>:
>
> Hi Sebastian,
>
> when you load a raw image directly with the editor the gamma is not set,
> meaning that the original linear curve of the cameras sensor is used.
> You can either shape the lightness correction curve to a convex form
> (last tab in the CM dialog). Or, which is easier,  use the
> Lightness/Contrast/Gamma filter afterwards and set the gamma to a value
> usually between 1.8 and 2.2. You may have to enhance the contrast
> afterwards. Find your raw image with gamma=2.2 and contrast=80 here:
>
> http://www.flickr.com/photo_zoom.gne?id=535788069&size=o
>
> Btw. I'm of the opinion, that opening a raw in the editor should set
> gamma and contrast to a reasonable value by default (or at least ask the
> user). I recently reported this as a bug, so I suggest you vote for it:
>
> http://bugs.kde.org/show_bug.cgi?id=146393



The reason that RAW 8 bits gamma is correct at loading in editor and not RAW
16 bits is duing to dcraw itself.

Look the dcraw web project page : in  16bits color depth,  RAW are converted
in linear mode without gamma correction. In 8 bits, the gamma is automaticly
corrected. This is why 16 bits color depth RAW file imported come become too
black...

I don't know why Dave have not add an option to auto-correct gamma with 16
bits color depth. The user must always has the possibility to do it.

Of course we can do it in digiKam automaticly, but if dcraw can do it
instead, like it do it with 8 bits color depth, this will be more
homogenous...

Gilles
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