Sony VGN-A170 - Manual (Page 18)

Additional information about adjusting the brightness of the LCD screen
Your computer comes with a brightness sensor that automatically increases and decreases the LCD screen's brightness
level depending on the amount of external light. The automatic sensor is engaged the first time you turn on your computer.
To override the automatic setting and manually adjust the brightness, follow these steps:
 Press the Brightness button, located next to the Volume buttons, and select one of the three brightness settings
(Auto, Brightness, or Max).
 Press the Fn and F6 keys to increase brightness.
 Press the Fn and F5 keys to decrease brightness.
Page 18