If you're not a fan of your iPhone's ability to adjust the screen brightness, you've probably already turned off automatic brightness several times in the past. All you'd do is go to your "Display & Brightness" settings and turn them off, but that's no longer the case in iOS 11 and iOS 12 – whether you have an iPhone X, X S X S Max, X R or any older supported iPhone
As you can see in the screenshot below, iOS 11 and 12, the Auto Brightness option is no longer available in the Display & Brightness settings. If you search for "Auto Brightness" in the Settings app, you will get to the new position of this setting, but not really, because you will need to tap it once to find the setting (if you can even remember what the
Apple makes us work for it. Now it's buried in the accessibility settings. To get there, select "General" in the Settings app and then "Accessibility." On the next page, tap Show Accommodations and you'll see the Auto Brightness switch.
Why has Apple made it more difficult for users to disable automatic brightness in iOS 11 and iOS 12? Who knows. Maybe they've been trying to reduce the number of people who complained about the awful battery life on their iPhone, which would explain the note in the settings: "Turning off automatic brightness could affect battery life." Still, I thought that was pretty obvious.
On OLED-equipped displays, it will also say in the headline "… and long-term display performance," if you look at the brightness for a long time is a static image, it could create a burn-in effect. Therefore, avoid having the same view on the screen at maximum brightness for an extended period of time.