this is what the manual says:
DISPLAY BRIGHTNESS & AUTO SHUTOFF
To bring up a brightness and auto shutoff time delay menu, press the UP and LEFT menu navigation buttons in rapid succession. Use the UP and DOWN buttons to switch between setting the brightness (from 1 to 4) and the time delay (from always on, 10 seconds, 1 minute, 5 minutes, etc.) using the LEFT & RIGHT buttons. The menu will dissappear approx. 10 seconds after the last button press.
Marius