i upgraded my laptop to windows 8.1, but i cannot find the driver for the brightness controller. the screen's backlight turns off when i set the brightness below 65%. i can still see the black screen with very dark apps. But the backlight is off. my question is how do i fix this? What is the driver for this? btw. I am using the laptop asus k52jr

1. Do you get any error message when you change the brightness on the computer?

You might be facing this issue because the display driver or the power plan which have created in your computer. SO I suggest you to perform the following trouble shooting steps and check if the issue persists.

Method 1:
Enable adaptive brightness
a. From the Start Screen, type Control Panel and select the Control Panel.
b. Set the View by: dropdown to Category
c. Select Hardware and Sound.
d. Select Power Options.
e. Select the Change plan settings link on your current power plan
f. Select Change advanced power settings
g. Expand Display
h. Expand Enable adaptive brightness
i. Change the setting to On and select OK.

Method 2:
If the issue persists, You can install the latest video card drivers from the manufacturer website and check.

http://support.asus.com/Download.aspx?SLanguage=en&m=K52JR&os=29

I suggest you to install the drivers in compatibility mode since there are no drivers available for Windows 8.

You can follow the link given below to install the driver in compatibility mode.