If you have an iPhone, you may’ve noticed its screen randomly dimming, even with the brightness slider on its maximum setting. There are a few reasons why this happens, starting with the most obvious, the auto brightness feature.
Most modern smartphones have an ambient light sensor that detects the brightness of your environment. When it’s dark, the backlight dims to make the screen less harsh to look at while also saving battery. If you’re outside in the sun, the display typically will reach peak brightness so you can still see your content.
But if auto brightness is turned off and the display still randomly dims, especially while outdoors in direct sunlight, it could be because the device is too hot.
When the iPhone overheats, it’ll go through a variety of actions to cool itself down.
And dimming the display is one of them, since it draws less power from the battery and generates less heat. You may also experience reduced performance and speed since slowing down the processor also reduces heat. If none of those actions work, and the iPhone’s temperature continues to rise, the last resort is a shut down, which it’ll do automatically.
But if your phone isn’t hot, then the True Tone feature could be to blame for the appearance of a dimming screen. It uses sensors to adjust the color and intensity of your display to match the ambient light, so that images appear more natural. But this change can make the screen appear dimmer than usual.
You can turn off this feature in settings to check how it effects your screen’s brightness.
Another feature with a similar dimming effect is Night Shift, which automatically activates at nighttime. It changes the tone of your screen to a warmer, orange color, filtering out the blue light. Now this technically shouldn’t effect the screen’s brightness. But it may cause content to be more difficult to see. Since the screen’s orange hue is uncomfortable for some people.
Finally, the iPhone’s display is set to dim after a certain period of time without interaction to save battery. This can also be changed in settings.