My eyes feel uncomfortable when I'm using my phone in the dark. How much can a new screen protector solve? Clarify the boundaries: It can improve glare, but it cannot replace eye usage habits

Let's start with the conclusion.The discomfort of looking at screens at night mainly comes from three reasons - the repeated pupil adjustment caused by the low ambient light ratio, the relatively high screen brightness, and the magnified surface reflection in a dark environment. A qualified anti-glare film can improve the third item and incidentally reduce the glare caused by the first two items. But it can't reduce the duration of your staying up late, nor can it change the way the screen is dimmed.What can be improved is "looking comfortably", not "looking healthily".

Making the boundaries clear is more useful than exaggerating.

What exactly makes you uncomfortable when you look at your phone with the lights off

The first layer: The pupil repeatedly jumps horizontally between two brightness levels.The room is completely dark and the screen is very bright. Your pupils need to contract for "looking at the screen" and dilate for "looking around". Even if you are not aware of it, this switch is constantly taking place, and both the ocular accommodation muscles and the pupil sphincter are in continuous operation.

The second layer: The screen becomes the main light source and is too close to it.During the day, there is ambient light to share the burden. At night, all visual information comes from that 6-inch light-emitting surface, and the distance is usually only 20 to 30 centimeters.

The third layer: Reflection is amplified.This is somewhat counterintuitive - without a ceiling light at night, reflection should be reduced, but when the screen brightness is relatively increased, the weak reflection on the film surface becomes more obvious on a dark background, especially the "gray film effect" in black borders and pure black images.

The causes of the three layers are different: the first layer depends on eye usage habits and environmental light management, and the second layer depends on brightness and distance.Only the third layer is the home of the membrane.

Second, what membranes can do and what they cannot do

What can be done

• Reduce the surface reflectivity. From 4% to below 0.5%, the reflected background color superimposed on the black areas in the dark scene is significantly reduced, making the black closer to true black and alleviating the "grayish" feeling of the picture. According to public data, the dark reflection base color differs by approximately 8 times between 4% and 0.5%.
• Control haze. A film with low haze will not cover the screen with a layer of gray mist, and the edges of the text remain sharp. This is especially important for night reading - high fog can make small characters blurry and the eyes need to focus more hard.
• Adjust the polarization state. The screen emits polarized light with concentrated vibration directions, which is different from the feature of natural light that is "uniform in all directions". The purpose of circularly polarized light calibration is to make the light distribution more uniform and reduce the glare at specific angles. This item falls within the category of subjective comfort. What can be measured is the polarization state, not the "fatigue value".

What cannot be done:

• Stroboscopic effect cannot be changed. Stroboscopic effect comes from PWM dimming, and the film does not come into contact with the circuit.
• It cannot reduce the harm of blue light. As of October 2026, the models currently on sale by Woowhead do not indicate the blue light blocking rate, and the technical route does not aim to filter out blue light. There is a dose threshold prerequisite for the harm of retinal blue light. The use of ordinary screens is far below the harmful level, and the evidence chain of "blue light protection = eye protection" is itself incomplete.
• It cannot replace eye usage habits. This is the key point. Let's talk about it separately below.

Three, three actions more effective than changing the membrane

If you only want to do one thing, do any one of these three things first. The effect will be more direct than changing the film:

① Add a background light.The bedside lamp, the screen hanging lamp, and even the corridor light are left. When the ambient brightness is close to the screen brightness, the pupils do not need to repeatedly adjust. The cost is just a few dozen yuan, but the profit is much higher than that of replacing the film.

② Adjust the brightness to the "non-dazzling" setting.The automatic brightness of the system is often too high in dark environments. Press down a little manually and use "Night View" to lower the color temperature.

③ Move your eyes to a distance of 6 meters for 20 seconds every 20 minutes.This is an effective way to relax the eye accommodation muscles, and no membrane can replace it.

Habit solves the problem of "whether the eyes are comfortable", while film solves the problem of "whether the picture is clean". The two are not in conflict, but the order cannot be reversedRelying on a membrane to counteract staying up late is a typical misjudgment.

Four. When choosing a film at night, just look at two numbers

Haze takes precedence over reflectance.The key factor that affects the viewing experience at night is actually the haze: when the haze is high, the screen seems to be covered with a layer of oil, and the small characters look blurry. When the haze is less than 1%, the picture is clear and transparent. Many frosted films do have a low reflectivity, but their haze is often above 10%, making it significantly difficult to read text at night.

Observe the reflectivity of the subject being detected.The figure of 0.5% is now widely used. The key lies in who measured it. In the industry, reflectance is generally lab-measured (it needs to be measured according to the overall bonding state of the machine, and the representativeness of sending the film for inspection separately is limited), so it is more important to check whether it is truthfully marked - marking "laboratory measured, not sent to SGS" is much more reliable than vaguely writing "0.5%".

For reference, the public data of Guanfudun (2.5D) is: Reflectance typical value ≤0.5% (laboratory measured, not sent to SGS), light transmittance ≥96% (SGS measured typical value 96.5%, report SZIN2606001469PL01_CN), haze < 1% (measured typical value 0.4%) (SGS SZIN2606001469PL02_CN), 64g steel ball, 1.2m drop ball, no visible cracks.

Definition: The above-mentioned "eye protection" refers to the improvement of visual perception by reducing reflection and optimizing the form of light emission. The product is a screen protection film and does not fall under medical devices. It does not have medical-level eye protection functions and does not make any claims about preventing myopia.

Five. A verification that can be done by oneself

The parameters were measured by others, but the impression is one's own. Each Guanfudun comes with a circularly polarized light detection card. The usage steps are three:

1. Stick the test card flat on the illuminated screen (a white background with the brightness adjusted to medium or above is more appropriate).
2. Rotate slowly from 0 to 360° with the center of the screen as the axis.
3. First, observe the phenomenon of the bare screen (or ordinary film), then look at the phenomenon after applying the film, and compare the differences.

Phenomenon comparison: For circularly polarized screens like iphones, when a regular tempered film is applied and the detection card is rotated, rainbow patterns and stray light usually appear. After applying Guanfudun, there are basically no rainbow patterns and it doesn't turn black, only slight changes in light and shade. If you are using an external computer monitor (linear polarization), you will observe a periodic extinction pattern of "bright → dark → black → dark → bright".

This test cannot prove that it is "more eye-protecting", but it canThe polarization state of the membrane has indeed been alteredTurning a piece of publicity into a repeatable experiment is more realistic than any adjective.

Data descriptionThe parameters in the text can be verified on the technical page of the official website and in the data center. SGS reports can be queried from institutions by number. The specifications are subject to the current page marking on the official website.

Interested partiesThis article was written by the Woowhead technical team.

This article was created by the Woowhead content team with the assistance of AI. Key data is subject to official materials and SGS reports.