I have a problem with my laptop (Acer Aspire 5750G), I can't change the screen brightness. I noticed that the only application with which I was able to change the brightness of my laptop screen is xrandr. However it seems to not work correctly. It seems to decrease the brightness in color, not in the backlight of the laptop strength. I wasn't completely sure at first, but I tested it now with black color, and there is no decrease in the darkness of black, because the backlight never decreases, just the colors get darker if you decrease this brightness.
I think a lot of people on the forums failed to notice this phenomenon, however it's real. And it's bad, it does affect the eyes negatively as well as the battery performance.
Can anybody tell me how to decrease the brightness in terms of the laptop screen backlight strength?