Have you noticed that the brightness of the screen on your Xiaomi, Redmi or POCO itself increases and decreases without your involvement? This is a common situation that can be annoying — especially if you are used to stable backlighting. 90% of the time, it is not the fault, but the built-in adaptive brightness feature, but sometimes the reasons lie deeper, from light sensor failures to firmware errors.
In this article, we will go into detail about all the possible reasons why the brightness on Xiaomi changes on its own, and give step-by-step instructions for eliminating them. You'll learn how to turn off automatic adjustment, check the light sensor, reset the screen settings, and even fix software errors if standard methods don't work. MIUI (12 to 14) and popular models from Redmi Note 10 Pro to Xiaomi 13 Ultra.
1. Adaptive brightness: how it works and why it is turned on by default
The main reason for spontaneous brightness changes is the Adaptive Brightness function, which analyzes the level of external lighting through the illumination sensor (located next to the front camera) and automatically adjusts the brightness of the screen for comfortable perception, for example, in a dark room the screen will dim, and in bright sun - will become as bright as possible.
Why is it on by default? Xiaomi has two goals:
- 🔋 Saving battery power – the lower the brightness, the longer the battery lives.
- 👁️ Vision care – sudden changes in brightness tire the eyes, especially in the dark.
- 📱 Standards compliance – many modern smartphones (including Samsung and Google Pixel) use similar algorithms.
But there are downsides to the function: it doesn't always work correctly, like the sensor can fire on reflected light or react with a delay, which causes brightness to jump when the light changes the slightest, and the adaptation algorithm in MIUI is not perfect, it often understates brightness even when it's not needed.
2. How to turn off automatic brightness control: step-by-step instructions
If you're annoyed by spontaneous brightness changes, the first thing you do is check if the adaptive lighting is on, and you can turn it off in 30 seconds.
- Open Settings (the gear icon on the main screen).
- Go to the Display section (or the Screen in older versions of MIUI).
- Find Adaptive Brightness (can be called Auto Brightness or Automatic Adjustment).
- Move the slider to the off position.
- For reliability, also turn off the sensitivity to light (if there is such a point).
Attention! On some models (e.g. POCO F3 or Xiaomi 12T), after the adaptive brightness is turned off, the safety mechanism may activate, the system will prompt it to be turned on again when the next lighting change occurs.
- 🔄 Restart the phone after disabling the function.
- 🚫 Special Opportunities menu → Improve visibility turn off automatic contrast setting.
☑️ Checking the Adaptive Brightness Shutdown
If after these actions the brightness still changes itself, the problem lies deeper - read the following sections.
Problems with the light sensor: how to check and fix
The light sensor is a small sensor next to the front camera that measures the level of light, and if it's contaminated, damaged, or malfunctioning, the brightness will change randomly. Here's how to diagnose the problem:
Signs of sensor malfunction:
- 🌓 Brightness jumps even in stable lighting (for example, in a room with the lights on).
- 🔦 The screen becomes too dark or too bright for no reason.
- 📱 In the adaptive brightness settings, the slider moves itself.
- 🚨 System Logs (available through Settings) → The phone. → Version. MIUI, 5 times, there are errors such as LightSensorError.
How to check the sensor:
- Open the Phone app and dial ##4636## (test menu opens).
- Select Sensors (Sensor Test)
- Look at the Light value – it should change when the lighting changes (for example, close the sensor with your finger – the value should drop to 0).
| Problem. | Possible cause | Decision |
|---|---|---|
| Sensor's not responding to light. | Sensor contamination or damage | Clean the sensor with a soft wipe; if it does not help - carry in the service |
| Values gallop randomly | Software failure or damage to the plume | Reset settings, update firmware or reflash your phone |
| The sensor is working, but the brightness is still changing. | Conflict with other functions (e.g., reading in the dark) | Disable all functions related to automatic screen change |
If the sensor is physically damaged (for example, after a phone crash), it will cost 800-1,500 rubles to replace it, depending on the model. AMOLED-The sensor is often integrated into the display module, so repairs can be more expensive.
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To temporarily trick the sensor into detecting brightness, stick a piece of opaque tape (such as tape) over it, which will help to check whether it is the fault of the problem.
4. Firmware failures and MIUI errors: how to fix software
Sometimes the brightness changes itself due to firmware bugs, especially after the MIUI update. For example, MIUI 13.0.4-13.0.6 had a massive bug in which the system ignored manual brightness settings. And in MIUI 14, some users complain of adaptive brightness conflict with Super Wallpapers.
How to fix software failures:
- Update the firmware: Go to Settings → About Phone → Update. If a new version is available, install it. Often bugs are fixed in the next patches.
- Reset the screen settings: Open Settings → Display → Additional (or Reset screen settings). Select Reset brightness settings.
- Clear the system cache: In Settings → Memory. → Clean up, click Clear cache. Or through Settings. → Annexes → Application management → Three points. → Show system-based → Systemic UI, then the Warehouse → Clear the cache.
- Reverse to the old version of MIUI (if the bug appeared after the update): Download stable firmware from the official Xiaomi website. Set through Settings → About phone → MIUI version → Three dots → Select a firmware file.
In versions of MIUI 14.0.3-14.0.5 there is a hidden function of forced shutdown of adaptive brightness via ADB. To do this, connect the phone to the PC, turn on USB debugging and execute the command:
adb shell settings put system screen_brightness_mode 0After that, the brightness is fixed at the current level, even if the adaptive lighting is turned on in the settings.
What if the brightness became too low after the MIUI update?
5. Conflict with applications and functions: what prevents stable brightness
Even if adaptive brightness is turned off, some MIUI apps and features may interfere with screen settings.
- 🌙 Dark theme and night mode: Dark theme and night light (in Settings) → Displays can automatically dim in the dark, turn them off or manually adjust the schedule.
- 📖 Reading Mode: In Settings → Display. → Read Mode check if Auto Turn on is enabled, which dims the screen when you run certain apps (like Google Books or Google Books). WPS Office).
- 🔋 Energy saving modes: C Settings → Battery turn off Ultra Mode or Supersaving – they are strong to reduce brightness to save charge.
- 🎮 Game mode: in Xiaomi and POCO There is a function of the Game Turbo (Settings) → Special facilities → Game mode, which can block the brightness changes in games, sometimes it works in regular applications.
Also check the permissions for applications:
- Open Settings → Applications → Application Management.
- Choose an app that can affect brightness (such as Twilight, Lux Auto Brightness, or Blue Light Filter).
- Disable it from accessing System Settings or Sensors.
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If the brightness changes only in a particular app (like Instagram or TikTok), the problem isn't with the phone, but with the app itself.
6. Hardware problems: when it is not the software that is to blame, but the iron
If all software methods have been tried, but the brightness still changes by itself, there may be hardware malfunctions.
| Symptoms. | Probable cause | Cost of repair (approximately) |
|---|---|---|
| Brightness jumps when you press the screen or body | Display plume or light sensor contacts damaged | 1 000–2 500 ₽ |
| The screen flickers or spontaneously dims | Failure to light up (especially on the AMOLED-screen) | 3 000–8 000 ₽ (screen-replacement) |
| The brightness changes only when charging. | Problems with the power controller or battery | 1 500–4 000 ₽ |
| The light sensor doesn't respond at all. | Failure of the sensor or control chip | 800–2 000 ₽ |
How to diagnose a hardware problem:
- Check if there were any physical damage (falls, moisture).
- Connect your phone to a knowingly serviceable charger – sometimes brightness jumps are associated with unstable power.
- Try running your phone in Safe Mode (hold the power button → long tap on Turn off → Safe Mode). If it's brightness stable, it's the software's fault, if it's not, it's the iron.
⚠️ If you suspect a hardware malfunction, don’t try to disassemble the phone yourself – especially if you have a model with a computer. AMOLED-screen (e.g. Xiaomi) 12S Ultra or Redmi K50 Pro. Improper repairs can result in complete failure of the display or loss of leakage (on protected devices). IP53/IP68).
7. Specific cases: features of different Xiaomi models
Some Xiaomi, Redmi and POCO models have unique brightness adjustment features, and these are the most common:
- 📱 Xiaomi 11T/11T Pro and 12/12 Pro: These models have AdaptiveSync (Adaptive Screen Update Rate) that can conflict with adaptive brightness. Turn it off in Settings → Display. → Screen refresh rate.
- 🎮 POCO F3/F4 GT redmi K40/K50: In gaming smartphones POCO Redmi K brightness may change due to Game Turbo. → Special facilities → Game mode.
- 🌈 Xiaomi Civi 1S/2 Redmi Note 10/11: On these models, a spontaneous brightness bug is often associated with Super Wallpapers wallpapers.
For models with MIUI for the global market (e.g. Xiaomi 13 Lite or POCO X5 Pro), a switch to European firmware (EU ROM) can help. It is often better optimized and free of some Chinese build bugs. However, note that this will require unlocking the bootloader, which voids the warranty.