Have you ever noticed your screen suddenly dimming or brightening all by itself? That’s auto brightness at work. This feature automatically adjusts your screen’s brightness depending on its environment. Basically, your phone screen will dim to complement the luminescence of a fancy candlelit dinner, but will brighten way up if you’re outside picnicking on a sunny day.
Want to see it in action? If it’s on your device, cover up the light sensor on your phone for a few seconds (it’s usually on the top of the front-facing side of your device) and your screen should compensate accordingly.
In theory, the feature is great. If you primarily use your phone in similarly lit indoor environments, then you might not even realize you have it. However, it tends to overcompensate a bit too much (and too suddenly) in either direction.
Auto brightness is on by default on most Android systems. If you don’t have any problems with it, then let it be. However, if you’ve found it to be a bit jarring, you can turn it off by going to Settings > Display. In some versions of Android, this screen-brightness setting will be available in the pull-down shade (but more on that later). With auto brightness turned off, you can choose a static lighting setting to your liking and manually move as necessary (but keep in mind that a brighter screen burns up more juice).