Sometimes you may notice that your iPhone's automatic brightness sensor doesn't work properly, such as your phone can't respond to changes in lighting, and the screen on the iPhone is still bright in the dark. Here is how you recalibrate it.
- Click the setting button, go to Settings.
- Scroll down and tap Display & Brightness.
- Swipe Auto-Brightness into the white/blank Off position.
- Move to a dark/dimly lit room, and then manually turn the Brightness all the way down, so the screen is as dark as possible.
- Swipe Auto-Brightness into the green On position.