imesh274 wrote:
94%
Ok, automatic brightness decreasing is usually caused by your device becoming too hot, so it automatically decreases the brightness to try and cool itself off. I think this is what you are seeing.
Next time this happens, feel the device’s screen with the back of your hand. If it’s hot then my theory is confirmed. However it’s not any cause for alarm. Your iPhone has built in temp sensors, and will do things to protect itself from overheating, such as lowering the brightness. And you will see an alert onscreen when the iPhone does actually overheat.