Answer: The screen brightness is controlled via GPS signal. The system will automatically switch between day and night illumination mode, triggered by GPS time stamp. In order to work the way it was designed, device requires GPS signal reception, causing a 20 seconds delay for the application to switch, right after device is powered ON. Go to (Setup > Video > Picture) and enter preset values for day and night brightness. You may also override the automatic GPS commutation to manual control, by changing the navigation settings respectively (NAV > More > Setting s> Map settings > Colour > Auto/Day/Night).