The screen has become the main point of contact between the user and their smartphone. On the Xiaomi 13, the display quality is often praised for its brightness and contrast. However, a much more discreet parameter raises questions among some users: the 240 Hz PWM. Behind this acronym lies a brightness management method that can cause eye discomfort in sensitive individuals. From headaches to a feeling of visual tension and prolonged discomfort, the subject deserves particular attention, especially since these effects do not affect everyone in the same way.
The Xiaomi 13 uses an OLED screen, a technology where each pixel emits its own light. To adjust brightness, the smartphone does not always reduce the light intensity continuously. It uses a process called PWM, for Pulse Width Modulation.
In practice, brightness is controlled by a very rapid alternation between turning the pixels on and off. At 240 Hz, the screen flickers 240 times per second. This flickering is invisible to the naked eye for most users, but it can be perceived indirectly by the visual system, especially at low brightness.
The lower the frequency, the more likely the phenomenon is to cause discomfort in some people.
Sensitivity to PWM varies greatly from one individual to another. Some people can use a 240 Hz screen for hours without feeling any discomfort. Others, however, experience rapid fatigue, sometimes within minutes.
Ophthalmologists explain this phenomenon by the permanent micro-adaptation of the eye. Even if the flickering is not consciously perceived, the brain processes these light variations. In sensitive individuals, this can lead to progressive visual overload.
According to a study published in the Journal of Vision, about 10 to 15% of users are sensitive to low PWM frequencies, with more pronounced symptoms in dark environments.
On the Xiaomi 13, PWM becomes more present when brightness is reduced. Indoors or in the evening, the screen lowers its intensity, which increases the duration of the pixel off phases. The flickering then becomes more pronounced.
Measurements conducted by independent laboratories show that, under 30% brightness, the PWM amplitude increases significantly. It is under these conditions that sensitive users most often experience eye strain, tingling, or a sensation of pressure behind the eyes.
At high brightness, PWM is less perceptible because the on phases are longer and more regular.
Oscilloscope analyses confirm that the Xiaomi 13 indeed uses a 240 Hz PWM, without automatic switching to a higher frequency. By comparison, some recent smartphones adopt frequencies of 480 Hz, 960 Hz, or even 1920 Hz, which greatly reduces the perception of flickering.
On the Xiaomi 13, the signal amplitude remains stable, but the frequency can be problematic for the most sensitive users. The measurements also indicate that PWM is active over a wide range of brightness, not just at very low levels.
Feedback from affected users mentions recurring sensations. The most common are rapid visual fatigue, difficulty focusing on the screen for a long time, and sometimes mild to moderate headaches.
In some cases, discomfort appears after 20 to 30 minutes of continuous use, especially when reading or scrolling through text content for extended periods. These symptoms generally disappear after a break, reinforcing the link with screen exposure.
It is important to note that these effects are not universal and concern a minority of users.
PWM is not unique to the Xiaomi 13. Most OLED screens use it. The difference lies in the frequency used and how brightness is managed.
A screen at 240 Hz produces slower flickering than a screen at 960 Hz. Even if both remain invisible to the naked eye, the nervous system can react differently. This is why some users feel comfortable on a recent OLED smartphone but experience discomfort on another model that is comparable on paper.
Even though the PWM frequency of the Xiaomi 13 cannot be directly modified, several solutions can reduce discomfort. One of the most effective is to slightly increase the brightness, even indoors. This reduces the flickering amplitude and makes the phenomenon less perceptible.
Activating the dark mode can also help by limiting very bright areas and reducing aggressive contrasts. Some users notice a significant improvement by combining moderate brightness and a dark theme.
The Xiaomi 13 includes an adjustable blue light filter. Although this filter does not directly affect PWM, it helps reduce overall visual tension. By decreasing the blue component, the eye exerts less adaptation effort, especially in the evening.
Studies indicate that reducing blue light can decrease the sensation of visual fatigue by 15 to 25% in users exposed to a screen for long periods. Combined with well-adjusted brightness, this option provides additional comfort.