How to Fix Your Phone's Brightness Settings Go easy on your eyes. Courtney Linder/PM It's a tough balancing act between trying to read a too-dark phone screen in broad daylight, or squinting to protect your eyes from what feels like the rays of 40 suns beaming out at you from your screen at night. ➡ Join Problem #1: My screen brightness keeps shifting. The likely culprit is your auto brightness setting–it doesn't always match your preferences, meaning it can surprise you with a blinding or frustratingly dull screen at inopportune moments. Auto brightness does have its purpose, though. A screen blasting bright, white light all day long will kill your phone battery faster than you can say, "Can I borrow your charger?"