Brightness settings are a recurrent sore point on Toshiba laptops using Linux.
When I bought this one 18 months ago, after trying unsuccessfully many methods found on support threads, I had been able to find a satisfactory way to reduce the glare of my laptop. I used the version of NVIDIA X Server settings I had found at that time on Linux Mint. Contrary to the current version you can now find coming with UP6, it included a part with a diagram where I could change the brightness settings. It also allowed me to produce a .nvidia-settings.rc file which memorized the chosen settings on start-up. I considered the problem as solved.
On UP5, the situation was slightly worse, I had to start again the NVIDIA X Server Settings to make him remember but it worked. I would like to use again the old NVIDIA X Server Settings of 18 months ago or to force the one of today to use the old file. I preciously kept the original .nvidia-settings.rc file but this file seems to be of no use now on UP6.
This is the original working one which is now consistently erased and replaced... If somebody can help because I cannot stand the glare of my laptop.
# Configuration file for nvidia-settings - the NVIDIA X Server Settings utility
# Generated on Thu Dec 27 15:19:21 2012
RcFileLocale = C
ToolTips = Yes
DisplayStatusBar = Yes
SliderTextEntries = Yes
IncludeDisplayNameInConfigFile = No
ShowQuitDialog = Yes
Timer = PowerMizer_Monitor_(GPU_0),Yes,1000
Timer = Thermal_Monitor_(GPU_0),Yes,1000