Why does the LCD brightness become brighter or darker automatically?

The LCD brightness becomes brighter or darker automatically.

This computer is equipped with the automatic adjustment function which will measure the ambient illuminance of the computer and optimize the LCD brightness accordingly. This function, as known as "Luminous sensor" is set to on by default.

However, the brightness can be adjusted using the Brightness button or Hotkey function Fn + F5 or F6. Switching the power settings through plugging or unplugging the AC adapter will restore back to the settings in the VAIO Power Management.

Please follow the steps below to disable the Luminous sensor function:

1. Choose Brightness or Max setting using the Brightness button.
2. Click Start and click Control Panel.
3. Click Performance and Maintenance and click Power Options.
4. Click Power Scheme tab and select any desired power setting.
5. Click VAIO Power Management tab and make the following settings:
- Item: LCD
- Plugged in: No Change
- Running on batteries: No Change
6. Click OK.

Note: Pressing the Brightness button will switch between manual, maximum and automatic brightness levels.