monitor too much bright?

It's the case of my glossy display (acer 2920) so I discovered that, under ubuntu, a gamma set to 0.6 it surely better:

1. how to find your preferred gamma settings:
   xgamma -gamma .6
   this will set both colors (rgb) to 0.6 value
2. alternatively it is possible to change each color as in the following example:
   xgamma -rgamma .6 -ggamma .8 -bgamma .6
3. Once discovered the right equilibrium among gammaa values, if you have the superuser rights you can set the xorg configuration in this manner:
   "sudo gedit /etc/X11/xorg.conf"
   modify the monitor section as follows, with your gamma values:
   
   

   Section "Monitor"
     Identifier      "Configured Monitor"
     Gamma           1.03 0.86 0.67
   EndSection
   

   
   
4. If you are not super user enabled???
   
   Open: System->Preferences->Sessions
   Press: Add
   
   Name: Gamma Settings
   Command: xgamma -gamma .6
   Description: optional