[argyllcms] Re: widegamut LCDs and internal LUT

Alexandre Prokoudine píše v St 24. 09. 2008 v 16:09 +0000:

> On Mon, Sep 22, 2008 at 5:23 PM, Hal V. Engel wrote:
> 
> >> To point 2 I would like to add, that this would certainly be nice for
> >> xcalib (@Graeme: you probably would agree on this for dispwin as well ;)
> >> )> but so far it's unclear for me how to add this without a certain
> >> amount of DDC/CI support inside xcalib.
> >
> > This is not needed since there is no need to load the internal LUT other 
> > than
> > at the time of calibration.   Once the monitors LUTs are loaded this is
> > persistant and is not lost across reboots.  IE. this makes boot loaders
> > obolete.
> 
> Does it mean that I can do calibration/profiling on Windows once (of
> course, in controlled lighting environment), then switch to Linux and
> never get back?


I can confirm Hal's  information, at least for Samsung LCD with LED
backlight (XL20? I am not at my comp now).

The display has several user-selectable modes, all can be operated with
buttons on the display. Two modes allow the user to save whatever
"profile" he wants. I use one for sRGB and the other one for monitorr's
native gamut (close to Adobe RGB).

The proprietary software for MS Windows allows to calibrate and
characterise the monitor, then loads the LUT adjustments to the monitor
via DVI cable. These settings stay in the monitor even after unplugging
the power cord. (The ICC profiles do not have any vcgt tag.)

So my approach was to create two hardware calibrations in the
proprietary software, then switch to linux and use argyll to create ICC
profiles of the monitor again (I use the native brightness, gamma and
white point). This allows me to use more patches then the proprietary
software. I leave the hardware calibration  as-is now and just
re-profile when needed.

Since I use hardware buttons for switching the modes, I placed two
scripts on my desktop to manually update the monitor.icc symbolic link
to refer to the "correct" profile and also re-run dispwin (or xcalib) to
update video-card LUT and let X know about the monitor's profile. Since
i use monitor.icc symlink, it is enough to restart the applications
(UFRaw, CinePaint) to load to correct profile.

Best regards,

Milan Knizek
knizek (dot) confy (at) volny (dot) cz
http://www.milan-knizek.net - about linux and photography

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