How to turn off autobrightness on Xiaomi Redmi 9: the complete guide

Many budget smartphone owners face a situation where the screen spontaneously changes the level of glow, which is often annoying and interferes with comfortable work. Automatic adjustment on the Xiaomi Redmi 9 model can be too aggressive, darkening the display at the wrong time or twisting the brightness to the maximum at the slightest change in lighting. This not only reduces usability, but also negatively affects the battery life of the device.

Fortunately, the MIUI operating system that runs the smartphone provides flexible tools to manage these parameters. The user does not have to put up with inconvenience or look for third-party applications that can disrupt the stability of the system. In this article, we will discuss in detail all the available ways to control the light sensor, including standard settings and hidden functions.

Unlocking the full potential of the screen requires understanding exactly how the calibration algorithm works in your particular instance of device. Sometimes the problem isn't software failure, but especially the proximity sensor, which is often combined with a light sensor. The right setup will allow you to forget about the constant twisting of the slider and enjoy a stable picture in all conditions.

Standard methods of brightness control in MIUI

The most obvious and affordable way to control the screen is in the notification curtain interface. On Redmi 9, this control is quite convenient, but many users do not notice the hidden switches. First, you need to unlock the device and swipe from the top edge of the display down to open the quick access panel.

In the menu that opens, you'll see a slider that's responsible for the level of lighting, and on the left or right of it (depending on the version of MIUI), there's often a sun icon or an "A." This symbol is the automatic mode activation symbol, and if it's on or off, it means that the system makes its own decisions about lighting.

To take full control, just click on this icon, deactivating the function, and then the slider will be fully manually controlled, but it is worth remembering that in some versions of the firmware, the algorithm may try to "tell" you the optimal values, if you do not change the position of the slider for a long time.

• 🌞 Open the notification curtain with a swipe from top to bottom.
• 🖐 Find the brightness slider and the “A” icon or sun next to it.
• 🚫 Click on the icon to turn grey or disappear, turning off auto mode.
• 📉 Manually set a comfortable level for your eyes lighting.

Importantly, once you turn off the automation, you'll have to respond to the change of environment on your own. Going from a dark room to a bright sun will require manual adjustments, because the light sensor will no longer affect the screen programmatically, a tradeoff between comfort out of the box and full control of the device.

Customization through the “More” menu and adaptive brightness

If simply switching in the curtain isn't enough, or you want to fine-tune the display behavior more, you should refer to the full settings menu. The path to these is standard for the Xiaomi ecosystem: go to Settings → Screen. Here lies a deeper level of image parameter management.

In the screen settings section, there is often an option called Adaptive Brightness or Auto Brightness. Unlike just turning on/off in the curtain, you can sometimes find additional options that depend on the version of the shell. Some users note that resetting the settings in this menu helps the recalibrate sensor if it starts to work incorrectly.

⚠️ Warning: If the brightness still jumps after switching the sliders, it is possible that a low-quality protective film is installed on the screen, which covers the sensor located in the upper frame or under the display.

This section may also include Read Mode or Eye Protection, which also affect perceived brightness and color temperature, and disabling these features may create the illusion that autobrightness is not working properly, even though different blue light filters are in conflict.

Remember that Redmi 9 is equipped with an IPS-matrix, which has its own features of color reproduction at different viewing angles and light levels. Optimal setting in the menu allows you to minimize the load on the eyes, especially when using a smartphone in the evening, when sharp brightness differences are most noticeable and harmful.

Use of the Engineering Menu for Calibration

For advanced users who are faced with the fact that standard methods do not give the desired result, there is access to the engineering menu. This is a hidden part of the system, designed to test hardware components, on Xiaomi, it is logged in through a set of special code in the Phone application.

Enter the combination ##6484## or ##4636## (codes may vary depending on the regional version of the firmware). In the list you will find the item related to the display or sensor test. We are interested in the section where you can check the Light Sensor.

Enter in the phone: ##6484##


Selected Sensor Test -> Light Sensor

Inside the test, you can see the current sensor readings in the luxes. By closing and opening the top of the screen with your hand, you can track whether the sensor is responding at all. If the values don't change, the problem can be hardware. If they change, but the screen doesn't respond, software calibration is required, which is often available with the Calibration button on the same menu.

Use of engineering tools requires caution. Do not change the values, the purpose of which you are not sure, as this can lead to malfunctioning not only of the screen, but also other system components tied to the sensors.

Proximation sensor problems and their impact

A common cause of brightness glitches on the Redmi 9 is a collision between the proximity sensor and the light sensor. In this model, they are often located in close proximity to each other in the upper frame. If the proximity sensor “thinks” that the phone is near the ear (for example, due to a case or dirt), it can block the screen or reset brightness.

You can also check the work of this component through the engineering menu or special test apps from Google Play. Pay attention to the cleanness of the top of the smartphone. Fat spots, dust or improperly pasted protective glass can create an optical illusion for the sensor, causing the MIUI algorithms to be mistaken.

• 🧹 Wipe the top frame of the smartphone with a soft cloth.
• 📱 Check if the cover covers the sensor area.
• 🛠 Use the “Proximity Sensor” test in the engineering menu.
• 🔄 Restart the device after cleaning to reset the sensor cache.

In some cases, calibrating the proximity sensor helps, and in the engineering menu, you have to select the appropriate test, close the top of the screen with your hand, press the calibration button, and then remove your hand and press the confirmation button, and this will "teach" the controller the correct distance values.

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Use transparent cases with a notch under the speaker – this ensures that no sensor will be covered with plastic or silikon accessory.

If software methods fail and the sensor continues to behave chaoticly even after resetting, there may be a hardware defect, in which case turning off autobrightness becomes the only way to comfortably use the device, ignoring the readings of the faulty sensor.

Third-party screen management applications

When the built-in tools aren't enough, Google Play apps come to the rescue, and there are many utilities like Brightness Slider, Auto Brightness Controller, or Lux Auto Brightness that take control of the screen, and they let you create your own light profiles.

These apps often require special permissions, such as “over other windows” and access to system settings. Once installed, you can completely ignore Xiaomi’s standard autobrightness and use smoother or sharper lighting curves.

⚠️ Warning: Installing third-party applications that require deep system resolutions always carries a potential risk.

Some apps also allow you to tie the change in brightness to the time of day or to an application running, for example, you can set the automatic brightness reduction to a minimum when you start YouTube or Netflix, which is impossible to do with standard means without using Do Not Disturb modes.

The Impact of Brightness Settings on the Redmi 9 Battery

The screen is one of the main consumers of energy in any smartphone, and the Redmi 9 with its capacious battery 5020 mAh is no exception. LCD-matrix used in this model consumes energy in proportion to the level of backlight. The brighter the pixels (or rather, the backlight behind them), the faster the battery discharges.

By turning off the autobrightness and setting a fixed value, you can predict battery consumption. However, if you forget to turn down the brightness when you go to a dark room, the energy consumption will be unreasonably high. Conversely, too dim a screen in the sun will make you squint, but save you charge.

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The optimal brightness level for saving charge on the Redmi 9 is in the range of 30-45% when used indoors.

It is also worth mentioning the Dark Mode feature, although it has a greater impact on the subject. AMOLED-screens, on IPS-In Redmi 9, it also helps reduce overall light pollution and subjective brightness perception, allowing you to keep backlight at lower values without losing readability.