[Digikam-users] Showfoto and raw NEF files; Gamma and Linearity?

[Hal V. Engel]

On Monday 29 October 2007 08:33:55 Ari El wrote:
> Thanks for the hint on the workingspace... I'll definitely looks for
> another one. I thought adobergb1998 was wide-gamut, but I turned out i was
> wrong.
>
> On the other side, ufraw also uses lcms I believe, and  it loads the nikon
> profiles with no problem. Actually digikam also loads and shows the details
> of this profile. What I can't find is digikam's equivalent of the gamma and
> linearity that ufraw takes as an input necessary to do the raw
> conversion....
>
> thanks!

And that is one of the reasons you are getting different results.  And also 
why the profile you are using is not valid with showphoto.

>
> Hal V. Engel wrote:
> > On Sunday 28 October 2007 20:50:18 Ari El wrote:
> >> I've been using showfoto to do all my essential photo processing; I
> >> started
> >> to shoot raw in my nikon d80 and I'd like showfoto to do the raw
> >> conversion
> >> as well, since the recent versions do support color management.
> >>
> >> I've been playing with UFRaw and their posted D80 profile
> >> (http://ufraw.sourceforge.net/Colors/Nkx_D80_5_1691_06_000_434.icm),
> >> using
> >> gamma = 0.45 and linearity = 0 I get really good results (in the sense
> >> that
> >> it looks extremely similar to the cam's generated jpg)
> >>
> >> Now when I open the NEF with showfoto (ubuntu 7.10 / showfoto 0.6), i am
> >> presented with the color management dialog (or plugin); with it, I
> >> select the above mentioned input profile, and as workspace profile I
> >> select adobe
> >> rgb (same thing I do in UFRaw). However I can't find the way to set the
> >> gamma and linearity parameters in showfoto. The "target" displayed, and
> >> the
> >> result after I click OK, looks very different to the cam's generated
> >> jpg, with way too much color saturation.
> >>
> >> I guess I'm doing something wrong in showfoto here... can someone point
> >> me
> >> in the right direction?
> >
> > In general you should be using a profile that was created for your work
> > flow.
> > That is different work flows require different profiles and using
> > different
> > software means that you are using a different work flow.
> >
> > My experience with my D70 using a custom profile in UFRAW is that the
> > camera
> > gamut is significantly larger than AdobeRGB-1998.  AdobeRGB-1998 has a
> > gamut
> > that is about 50% of Lab and my D70 has a gamut that is closer to 70% of
> > Lab.
> > So you will definitely loose some gamut and dynamic range if you do a
> > conversion to a smaller color space like AdobeRGB-1998 at least for some
> > images.  So you may want ot consider using a working space with a larger
> > gamut.
> >
> >> ps. One thing I noticed is that, trying to set the default input profile
> >> in
> >> Settings > Configure Showfoto > Color management,  after I set the
> >> folder containing my profiles, the "Input" profile options listed
> >> include a few profiles I have in that folder but *none* of that folder's
> >> nikon profiles.
> >> For some reason my nikon profiles can not be set as the defaults. I can,
> >> as
> >> mentioned above, manually select the nikon input profile at the time I
> >> open
> >> each image.
> >
> > The Nikon profile may not be correctly tagged as an input profile and
> > smarter
> > dialogs for presenting lists of profiles to users will use these tags to
> > only
> > show input profiles or display profiles or printer profiles when this is
> > what
> > is called for.  For example, the profile widgets in LProf for selecting
> > proofing profiles do this.  So I would not be surprised if showfoto did
> > this
> > as well.
> >
> > Marti Maria, the author of LCMS, estimates that as many as 25% of the
> > profiles
> > out in the wild have at least something that does not meet the ICC
> > specification.  Perhaps your Nikon profile is one of these.
> >
> >
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