[Digikam-users] suddenly cannot choose a monitor profile in settings

[Martin (KDE)]

Am Dienstag, 22. Dezember 2009 schrieb Mark Greenwood:
> On Tuesday 22 Dec 2009 09:16:41 Martin (KDE) wrote:
> > Am Dienstag, 22. Dezember 2009 schrieb Guenther Erhard:
> > > > > I cannot find anywhere in system settings that allows me to
> > > > > select a profile. Nor can I find any reference to it in
> > > > > Google or by searching the KDE site.
> > > >
> > > > So may be it has something to do with this:
> > > > http://www.argyllcms.com/doc/dispwin.html#I
> > > >
> > > > It seems to go the same way as gimp and ufraw do it already.
> > > > A dialog to query currently set display profile would be fine
> > > > anyway.
> > >
> > > Yes, that is possible, but "set | grep ICC" does not show any
> > > set environment variable.
> >
> > The data is not stored in environment variables but as property
> > in X11. For the dispwin tool the configuration is set in
> > ~/.config/color.jcnf. My data is set as:
> >
> >   "devices": {
> >     "display": {
> >       "1": {
> >         "EDID":
> > "0x00FFFFFFFFFFFF0015C37916010101010C0E0102681E1778EAA415A5544897
> >250F5054BFEE000101010101010101010101010101010164190040410026301888
> >360030E410000018000000FF004B353134333033340A20202020000000FD00374C
> >183D08000A202020202020000000FC004C3336370A20202020202020200022",
> > "ICC_PROFILE":
> > "/home/blablub/.local/share/color/icc/devices/display/eizo.icc"
> >       },
> >       "2": {
> >         "NAME": ":0.0",
> >         "ICC_PROFILE":
> > "/home/blablub/.local/share/color/icc/devices/display/dell-L.icc"
> >       }
> >     }
> >   }
> >
> > If I load color profile (dispwin -L) the one for my current
> > display is loaded (here dell-L.icc) the eizo.icc I used with my
> > old monitor.
> >
> > > In my case I don't use dispwin - I use xcalib to load the
> > >  calibration profile at every startup of X11.
> >
> > I don't know xcalib, but it must do something similar.
> 
> Now I'm even more confused. I have never heard of xcalib or
>  dispwin.
> 
> I have a monitor profile for my monitor and I want Digikam to use
>  it. What is all this config files and load at startup of X11
>  nonsense?

Sorry Mark, this is no nonsens. for a colour managed environment you 
have to calibrate and profile your monitor. Usually this results in a 
icc or icm file.

The calibration stuff is loaded usually at login time. This sets your 
Gamma curve (and colour temperature) to what you have set up your icc 
profile to (I have a L-Star gamma and a colour temperature of about 
6500K - my native display colour).

The profile stuff is done by the application (digiKam, Gimp or UFRaw). 
So you have to either set it manually in every application or you can 
use the system wide profile (which is the one you loaded at login). 
This makes sure that red in sRBG is displayed ecactly as the same red 
as in AdobeRGB or eciRGB (as long as they are in the available range - 
called Gamut).

So If you want to use your Monitor profile reset all your monitor 
settings to default. Install argyllcms (or xcalib) and load the icc 
file at login (first time: dispwin -I /path/to/display.icc; next: 
dispwin -L). Next you have to load the file as display profile in your 
application.

Be aware: colour management does not improve the colour itself.

Next important step is to choose a working profile. Here you are free 
to choose every profile you want, but without a hardware calibrated 
monitor best use may be sRGB. AdobeRGB does not bring you more colour 
if your Monitor is not able to show it (which most monitors can not). 
Even worse: If you use 8-bit encoded RGB you loose some fine 
granularity in the less saturated part of the image.

Conclusio: If you want to use 8-Bit RGB use sRGB (you avoid problems 
if you print images or give them to others). If you want higher colour 
range use L*-RGB and 16-Bit. But then you have to buy a hardware 
colorimeter and a monitor which can display this colours reliably. 
This will you cost you at least 1000 Euro for the monitor and 250 Euro 
for the colorimeter.

Martin

> 
> Mark
>