Comment 17 for bug 392122

Have you tried unchecking the "reduce backlight brightness" option in power management?

I was seeing this problem under Ubuntu 11.04 on my 2nd-gen Core i7 laptop, that after dimming the brightness would always increase only to 50% regardless of what I had set the brightness to before.

However when I uncheck the "reduce backlight brightness" box for "on battery power" (which automatically reduces backlight when you disconnect from the AC supply) the dimming works as expected and afterwards returns my brightness to whatever level it was before it dimmed.