My latpad screen is too light, that cause my eye is very imcomfortable. So I spend time to hanle this problem. At result , I find the follow method:
1. open the following file on the root user.
/etc/udev/rules.d/81-backlight.rules
2. In the end of the file add following code.
#Set backlight level to 3
SUBSYSTEM=="backlight", ACTION=="add", KERNEL=="acpi_vido0", ATTR{brightness}=="8"
3. reboot your system.
You will find it is work.
This rules sets the backlight level to a fixed value.
If you have any question,please kick
https://wiki.archlinux.org/index.php/Backlight
Besides, my os is centos 7.0. my latpad is acr 4750.
Good for you,thanks.
Adjusting backlight to a fixed level.
原文：http://www.cnblogs.com/ordili/p/4039434.html