[Digikam-users] Color management behaviour

Mon Jun 22 11:41:14 BST 2009

Ok, thank you Gilles. Do you need a good summary of the issues? I mean
screenshots and test cases?

Leonardo

2009/6/22 Gilles Caulier <caulier.gilles at gmail.com>

> 2009/6/22 Leonardo Giordani <leonardo.giordani at treuropa.com>:
> > Francisco,
> >
> > thank you for you advices. I notice some inconsistency in color
> management,
> > though. My issues happen if I click on my RAW picture and open it with
> > "modify"; but if I use RAW importer as you suggested color management
> works
> > as expected.
> >
> > Developers, something to say about this?
>
> yes. Sound like something is broken in CM.
>
> There are few entry in bugzilla about this subject. sound like code is
> broken somewhere when port to Qt4 have been done.
>
> I will review code before 1.0.0 final release. For the moment i'm busy
> on other place (:=)))
>
> Gilles Caulier
>
> >
> > Summary: opening a RAW data asks for "Assign" or "Convert" to workspace,
> but
> > it works differently from how RAW importer works.
> >
> > Someone is experiencing the same issue (and the issues I talk about in my
> > first mail?)
> >
> > Thanks
> >
> > Leonardo
> >
> > 2009/6/19 Francisco Lorés Ara <plores at telefonica.net>
> >>
> >> Hi Leonardo,
> >>
> >> I'm quite a newbie on color management, but I'll try to describe my
> setup
> >> and workflow in the hope it helps you.
> >>
> >> I'm using an EOS 450D and digiKam 0.10.0 on openSuSE 11.1. The first
> thing
> >> with CR2 files is that they don't have an embedded or built-in color
> >> profile.
> >>
> >> But, we need to tell digiKam which is the camera profile. I've been
> >> wandering a while with Digital Photo Professional (the raw
> converter/editor
> >> supplied by Canon). At least in mine, the camera profiles can be found
> under
> >> the folder
> >>
> >> C:\Program Files\Canon\Digital Photo Professional\icc
> >>
> >> There are in fact a pair of ICC profiles, one for sRGB color space and
> one
> >> for
> >> AdobeRGB color space, for each picture style available
> >>
> >> Faithful: fs.icc, fa.icc
> >> Landscape: ls.icc, la.icc
> >> Neutral: ns.icc, na.icc
> >> Standard: ss.icc, sa.icc
> >> Portrait: ps.icc, pa.icc
> >>
> >> So if you work with sRGB colorspace, the suitable camera profiles should
> >> be fs.icc, ls.icc, ns.icc (*s.icc for sRGB), and so on. Copy them to
> >> /usr/share/color/icc under Linux and configure the path and preferred
> input
> >> profile on the Color Settings setup tab. These profiles are *not*
> identical
> >> to standard sRGB or Adobe RGB, they are specific to the camera model.
> This
> >> can be the reason you see the picture differently with/without color
> >> management.
> >>
> >> As for the monitor profile, monitors come frequently with a "driver" in
> >> CD, part of which is the monitor's color profile. For example, I own an
> LG
> >> Flatron (not quite a good display as I would be pleased to have ;-) ). I
> >> searched on the driver CD and found the file lh1970hr.icm, which is the
> >> display profile for this particular model. As before, I copied this file
> to
> >> /usr/share/color/icc and selected it in digiKam setup. And as before,
> the
> >> monitor's profile is *not* identical to standard sRGB (although
> >> approximate), it is specific to the display model.
> >>
> >> On the other hand, a distinction must be made between profiling and
> >> calibrating a monitor. Both are **essential** to have a good, or at
> least
> >> acceptable, color-managed workflow; otherwise you'll get
> under/overexposures
> >> while adjusting, as well as color shifts/casts. So in addition to
> getting a
> >> good monitor profile, you need to calibrate as much accurately as you
> can
> >> the monitor's black point, white point, and gamma. I suggest the methods
> >> described in the excellent tutorials and charts from Norman Koren at
> >>
> >> http://www.normankoren.com/makingfineprints1A.html
> >>
> >> which, if you don't need an extreme color accuracy, can be done
> "eyeball"
> >> without the need of a spectrometer.
> >>
> >> Personally I always shot RAW in Adobe RGB colorspace, as it is a bit
> wider
> >> than sRGB and well suited for editing / printing. On the RAW converter I
> >> select the Landscape Adobe RGB input profile (la.icc) for general use,
> but
> >> change it when appropiate (pa.icc for portraits for example).
> >>
> >> Once finished editing, I select Color -> Color Management, set Input
> >> Profile = Embedded profile, Workspace profile = sRGB and click OK to
> convert
> >> from Adobe to sRGB. Then I save the finished image in JPG or PNG format
> with
> >> sRGB embedded in it. In this way I see the picture OK in digiKam as well
> as
> >> in Gwenview or the GIMP.
> >>
> >> Maybe the camera profiles are different for your 350D, but you can
> install
> >> Digital Photo Professional in a Windoze box, and use the filemon.exe
> utility
> >> from Micro$oft
> >>
> >> http://technet.microsoft.com/en-us/sysinternals/bb896642.aspx
> >>
> >> to investigate which files are opened/used during conversion and
> editing.
> >> One or more of them will be the camera profiles :-)
> >>
> >>
> >> Wow, sorry for the length ;-) I hope that if something is wrong the
> >> "gurus" will reply with the truth (don't forget I'm also a newbie :-)),
> >> simply it works quite well for me.
> >>
> >> Regards,
> >>
> >> Francisco
> >>
> >>
> >
> > --
> > Leonardo Giordani
> >
> > Tele-Rilevamento Europa - T.R.E. s.r.l.
> > a POLIMI spin-off company
> > Via Vittoria Colonna, 7
> > 20149 Milano - Italia
> > tel.: +39.02.4343.121
> > fax: +39.02.4343.1230
> > e-mail: leonardo.giordani (at) treuropa.com
> > web: www.treuropa.com
> >
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> >
> >
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-- 
Leonardo Giordani

Tele-Rilevamento Europa - T.R.E. s.r.l.
a POLIMI spin-off company
Via Vittoria Colonna, 7
20149 Milano - Italia
tel.: +39.02.4343.121
fax: +39.02.4343.1230
e-mail: leonardo.giordani (at) treuropa.com
web: www.treuropa.com
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