windows 7 - My Lenovo IdeaPad screen went dim by accident

I accidentally pressed the wrong key (not sure which) while typing and my laptop's screen went dim. I can't get it to go back to how it was. (I'm using Windows 7 64 bit.) What should I do?

Answer

The pressed key was F11 (without the Fn key pressed). The IdeaPad uses this key for "decrease brightness". F12 should do the opposite, but doesn't always work. To get it working, you need to edit the registry:

1. Open/run regedit ¹


2. Navigate to HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000 ²


3. Set the value of "FeatureTestControl to 0000f048 (hexadecimal)


4. Reboot


5. When Windows starts (or at any point while running), use the F11 and F12 keys to adjust the brightness of your screen.

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1. You might need to reinstall drivers for your graphics cards before this step.


2. You might need to navigate to HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0001 instead of HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{4d36e968-e325-11ce-bfc1-08002be10318}\0000

Source: IdeaPad P500 screen went dim