Answer: The screen brightness is controlled via GPS. It is designed to automatically switch between day and night illuminations by evaluating the GPS time stamp. In order to do so, it needs GPS signal reception, which leads to a 20 seconds decision delay after powering the device 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 map settings (NAV> More> Settings> Map settings> Colour> Auto/Day/Night).