[SOLVED]Xrandr and xbacklight

Hi guys!
I am using Mageia 3 KDE and would like to adjust brightness at startup. I found that both xrandr --output LVDS1 --brightness 0 and xbacklight -set 0 have effect on brightness but do not actually know the difference between them. What is the difference and should I use both or just one of them is enough and if one which one is better?
Thanks!
I am using Mageia 3 KDE and would like to adjust brightness at startup. I found that both xrandr --output LVDS1 --brightness 0 and xbacklight -set 0 have effect on brightness but do not actually know the difference between them. What is the difference and should I use both or just one of them is enough and if one which one is better?
Thanks!