Panasonic CF-Y4 Reference Manual page 18

Using the Fn Key
Key
Fn+F1
LCD brightness control
(Fn+F1= down / Fn+F2= up)
Fn+F2
Pressing this key combination adjusts the LCD
brightness control.
You can select a different brightness level setting
for when the AC adaptor is connected and for
when it is not connected.
(At the time of purchase, the LCD brightness is set
to be darker when the AC adaptor is not
connected.)
NOTE
The brightness of the power indicator
( page
brightness level of the internal LCD.
Functions
23) changes in keeping with the
18
Pop-up Window
(Displayed after
logging on to
Windows)