The display backlight turns off if you do not press a key for the period of time selected. You can set the time from 5 to 60 seconds in increments of 5 seconds.
To change it from the factory default of 15 seconds, press MENU/SELECT.
Press MENU/SELECT.
Press 
or 
to change it.
Note: It will wrap around from 60 to 5.
Press MENU/SELECT when done.