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Bug#166413: mga driver doesn't set gamma on second screen

On Mon, 2002-10-28 at 17:55, Marc Wilson wrote:
> On Sun, Oct 27, 2002 at 11:14:37PM -0500, 166413@bugs.debian.org wrote:
> > On Sun, Oct 27, 2002 at 07:07:15PM -0800, Marc Wilson wrote:
> > > I always had the problem with my G450 and later with my G550 that X
> > > wouldn't set the gamma the same on both heads, although it claimed that it
> > > was according to the log.  The monitors were the same make and model, and
> > > the difference was distinct and annoying.
> > > 
> > > OTOH, xgamma was always quite willing to set the gamma on the heads
> > > separately, and I was also able to specify specific gamma settings for each
> > > monitor in XF86Config-4 and have them take effect.
> > 
> > In that case I'm confused.  Has there been a regression since XFree86
> > 4.1 or not?
> I should clarify...
> When I was still using the G450/G550, X would claim that it was setting the
> gamma on the two monitors identically.  Anyone who looked at them, though,
> would be able to tell that they were wildly different.
> I used xgamma (at first) in $HOME/.xsession, and later manipulating
> XF86Config-4 directly, to reduce the gamma on the second monitor, like so:
> Section "Monitor"
>         Identifier      "Viewsonic PF790"
>         HorizSync       30-97
>         VertRefresh     50-180
>         Option          "DPMS"  "Yes"
>         Gamma           0.8 0.8 1.15
> EndSection
> This was the only way I could make the two of them balance.  I always
> chalked it up to just hardware differences in the respective video outputs
> (ie they had different ideas of what gamma 1.0 meant) and got on with
> things.
> I haven't run either of my Matrox cards on XF 4.2.x... it's a nVidia world
> in my box now (I wouldn't have, but they were free).
> Sorry for any confusion I may have introduced.  I think I was trying to
> point out that even though they weren't being set the same (and X claimed
> they were), there was still individual control on both heads.

Every monitor has a characteristic color response curve; that's one
thing one can compensate for using xgamma. You can't expect the same
values to produce the same result on different monitors.

Earthling Michel Dänzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member   /  CS student, Free Software enthusiast

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