The screen has a light sensor on it (the little clear lens centered on the lower bezel). It auto dims according to ambient light. Put your finger on and off the lens and you will see the brightness change, You can set the baseline brightness in the "settings" menu. The brightness you set this to will be the brightness level when you turn on the lights and have the dash light knob all the way up. And you can use the dash light knob at night which will substantially reduce the screen brightness from the baseline level.
Problem is if you set the baseline brightness too low (comfortable at night with the dash lights all the way up), it won't be bright enough during the day. Nothing is ever perfect is it......