Since the latest update (7.11) the screen brightness in the home screen and the app drawer automatically dims when I pick the phone up. Not sure if this is a bug but I can't seem to find a setting to switch it off or control it.
That might be the effect of "Adaptive brightness" feature.
It adjusts the brightness according to your previous adjustments.
If disabling this option doesn't sort out this problem, then please share an error report via Beta Feedback option in Samsung Members app!