[Digikam-users] Re: Processing RAW images to get to the look of the jpg preview

[Martin (KDE)]

Am Freitag, 24. Juni 2011 schrieb Remco Viëtor:
> on Friday 24 June 2011, Sven Burmeister wrote:
> > Am Donnerstag, 23. Juni 2011, 11:48:20 schrieb Martin:
> > > I don't think your problem is gamma only. The gamma curve only
> > > depends on the colour model you use to view the picture (sRBG,
> > > Adobe RBG, Apple RGB ...). It should almost never be necessary
> > > to adjust this by hand. But I have no clue what the problem of
> > > digikam is here.
> > 
> > Could you please try the digikam demosaicing tool with highlights
> > set to "blend" or "rebuild". I tried to avoid the gamma setting
> > (1,7) but while it works without gamma and adjusting the
> > luminosity curve for most parts of the picture, areas that are
> > almost black (dark blue) remain far too dark. If I
> 
> use
> 
> > gamma it works better. So I wonder how it could be done without.
> 
> Iirc, Digikam (at least in certain modes) develops the RAW files
> with a linear curve (i.e. gamma=1.0), like dcraw in its default
> settings. So you will have to set gamma to the value you want (2.2
> usually, except for old Macs, that used 1.8). Luckily, the values
> you set is remembered for next use.

As digikam works with CMS this should never be necessary. If they use 
a gamma of 1.0 for raw development the display module has to take care 
to convert it to the display intent. This is why colour management 
systems are used.

By default most raw data are set with gamma to 1.0 (so not have a 
gamma set at all). During process they got a gamma of about 2.2 (for 
sRGB and AdobeRGB) or 1.8 (AppleRGB) or no gamma at all (LAB). It is 
up to the display or printing software to take the right gamma and 
recalculate it for the display or printer.

Martin

> 
> Remco