[Digikam-users] Color management behaviour

[Leonardo Giordani]

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?

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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