The screen brightness changes when the user opens, uses, or closes an app

1. You may have enabled Automatic on the brightness settings screen, resulting in the screen brightness automatically changing to a suitable level based on the environmental lighting conditions detected by the ambient light sensor on the top of the phone. (The screen brightness will decrease if the ambient light sensor is covered.) If you want the screen brightness to stay the same, open Settings, search for and touch Display & brightness/Brightness, disable Automatic, then adjust the screen brightness to the desired level manually.

2. If the screen brightness automatically increases or decreases when you open or exit an app, the possible causes are as follows:
   1. The app has adjusted the screen brightness itself. This is because the system brightness adjustment permission is open to third-party apps such as video, reader, and payment apps. For example, when scanning a QR code in Alipay, the screen brightness increases instantly. This is a normal phenomenon.
   2. To save power and for an optimal user experience, the system automatically changes the screen brightness in some scenarios. For example, the screen brightness automatically changes when using apps such as WeChat, Browser, Contacts, and Messaging, even if automatic brightness adjustment is disabled. This is a designed feature of your phone.
3. If your phone heats up and the screen brightness automatically decreases when you are using an app, it is because the screen brightness is lowered to prevent overheating (of CPU, battery, antenna, and other components). The screen brightness will return to normal after the phone cools down. This is a designed feature of your phone.

The screen brightness deceases when Automatic is enabled

Perform the following to troubleshoot:

1. Check whether the ambient light sensor on the phone is covered by a protective film or any foreign objects.
2. If you are in a dark environment, the ambient light sensor will detect that the lighting is weak, resulting in the screen brightness getting lower. It is recommended that you manually set the screen brightness in this case.
3. Check the ambient light sensor. If any of the following occurs, back up your data and take your device and proof of purchase to an authorised Huawei Customer Service Centre for assistance.

• When the Automatic switch is turned off, the screen brightness still changes automatically.
• When the Automatic switch is turned on, the screen brightness switches back and forth under a fixed light source (such as a torch).

The screen brightness automatically changes under strong lighting conditions when Automatic is disabled

• When the sensor detects that the ambient light reaches a certain level, your phone will automatically increase its screen brightness to improve your viewing experience. This is normal and please do not be concerned.
• To protect your eyesight, avoid staring at your phone when the ambient light is strong (such as in direct sunlight) for long periods of time.

The screen brightness is not decreased to the lowest level when the ambient light sensor is covered

The screen brightness adjustment mechanism has been optimised so that the screen brightness will not decrease to the lowest level when the ambient light sensor is covered. This helps to prevent the screen brightness from decreasing when the ambient light sensor is covered by mistake. To adjust the brightness to the lowest level, drag the brightness adjustment slider in the notification panel to the leftmost position.

It takes a short while for the screen to wake up after a call ends and the phone is moved away from the user's ear

To prevent the screen from being turned on during a call when the proximity sensor incorrectly detects that the phone is far away from your ear, a mechanism has been added so that it will take a short while for your phone screen to wake up in the preceding case.

When Eye Comfort is enabled, the screen will switch between white and yellow background colours, which resembles a change of screen brightness.

More knowledge:

When Auto-brightness is disabled, why does the displayed brightness differ from the level displayed in Phone Manager?

Screen brightness suddenly changes after swiping on the home screen when Wallpaper is set to Scrollable