Many people must have such an experience. After spending thousands of dollars to buy a mobile phone, and after using it for a period of time, they start to feel symptoms of eyestrain such as; headaches, soreness, tearing, pain, and easy visual fatigue. This is likely to be caused by low-frequency PWM. Caused by the dimming screen. Before we go ahead to discuss the effects of a smartphone with a low-frequency PWM dimming on the health of users, let’s first get started with the rudiments of the subject matter.
What exactly is PWM? PWM is the short form of pulse-width modulation and describes a flickering of the background illumination to reduce the luminance.
Due to the different perceptions of each human body, some users have little or no sensitivity to low-frequency PWM dimming and do not think that this dimming method will harm their health. Notebookcheck ranked all popular smartphones, past, and presence according to their PWM frequency rating, you may want to have a look.
I bought a 360Hz low-frequency PWM dimming mobile phone as the main phone at the beginning of July last year. It has been more than half a year now, and below are the results. I had a terrible experience.
Effects of a Smartphone with a low-frequency PWM Dimming
Please note that symptoms may not appear at the Beginning
As far as my experience is concerned, on paper, the low-frequency PWM dimming is at the level of “bearable and usable”. When I started using it, maybe I was still immersed in the joy of acquiring the new device, and I didn’t feel any discomfort.
After a period of time, I developed dry eye syndrome. I felt a burning sensation and itching in one of my eyes. When I was lying on the bed at night and looked at my mobile phone, my eyes were too dry and irritated, which stimulated reflexive tear secretion instead. This is what netizens often say. Said, “Look at the phone and cry”.
In the meantime, the above-mentioned situation was a normal situation, and the dry eye syndrome could be relieved by medicines, but eye itching, slight dryness, and teary eyes were still present occasionally, but they did not affect my life.
Must Read: How many of these phone manufacturers’ Marketing Gimmicks have you Fallen for?
List Of Some Phones That Are Good For Your Eyes Because They Have No PWM Issues
The general assumption is that you can find phones that have good PWM and won’t hurt your eyes among Android phones using Qualcomm snapdragon 695 and older chips. That notwithstanding, I will compile a list of phones that have good PWM and no flickering.
Sadly, most of these phones are old and not the latest flagships.
- Samsung GALAXY NOTE 5
- iPhone 11, not 11 pro
- iPhone SE with LCD screen
- Xiaomi redmi note 9 Pro max, from brightness above 44%
- iPhone XR
- Xiaomi Poco X4 GT and poco x3
- You can also try some Motorola phones with pOLED screens E.G; Motorola Edge 30 Fusion
- Motorola G60
- Fairphone 4 with Snapdragon 750G\
- Oneplus Nord ce2 Lite 5g
- Realme 9i
- Samsung A23 5g
- Samsung m33
- honor x8 and X9
- Moto g stylus
- Nokia G60
- Nokia G400
- Samsung Galaxy Xcover Pro 2
Samsung Galaxy Z flip4
Samsung Galaxy S10 Plus (PWM & Horrible Dithering)
Samsung Galaxy S21 FE (PWM & Horrible Dithering)
Realme 7 5G (No PWM, but it has horrible Dithering!)
How Badly Can a Smartphone with a Low-frequency PWM Affect Your Vision Health?
A friend of mine wasn’t as lucky. He had all the symptoms I had plus more. For him, when he went to the movies and looked at the huge screen in the distance, he realized that the pictures on the screen were not clear, and occasionally there were some double images.
Obviously, this is just a 2D movie without 3D glasses. The same is true for watching TV. It is Only when the TV is in front of you that you can see the picture that is being displayed clearly.
Regarding the health problems induced by low-frequency PWM dimming, Samsung officials have publicly stated that this dimming method may cause headaches, eye fatigue, and vision loss. As one of the purchasers of Samsung screens, mobile phone manufacturers are not ignorant of the problem of this dimming method, so some manufacturers have built a “low flicker mode” in the developer mode to reduce the stroboscopic index.
The problem is that although it can alleviate the negative impact of low-frequency PWM dimming to a certain extent, the actual effect is not enough. Because this mode is only effective at low brightness.
If conditions permit, pushing DC dimming firmware is a more ideal solution.
How Do The effects of a Smartphone with a Low-frequency PWM Affect Various People?
Do those people who are not very sensitive to low-frequency PWM dimming also experience the above symptom? It has appeared, but the conclusions drawn by people on different platforms are somewhat different.
Some users claim to be insensitive to stroboscopic flicker, but after using it for a period of time, they still experience eye swelling and headaches.
Some just played a game for more than 20 minutes, and their eyes hurt a little. There are also some users who find that their eyes cannot focus and cannot see the screen clearly when looking at the same screen.
Vertical platform users, very clearly point the problem to low-frequency PWM dimming. If it is a search engine-related question for a wider group of people, it will generally point to eye fatigue and the OLED screen itself, especially the latter.
In July 2019, I searched for “Does OLED screen hurts eyes” on Google. At that time, there were nearly 3,000,000 related links. 2021 to 2022 happens to be two years when low-frequency PWM dimming is popular on mobile phones.
But these two years happened to be the two years when Chinese screens and high-frequency PWM dimming gradually emerged in the mobile phone market, and they are equipped with the dimming methods that we often recommend in evaluations and shopping guides.
Pay Attention to High-Frequency PWM Dimming When Buying A Device With LCD/OLED
Different elements correspond to different symptoms. The stroboscopic effect is on the front of the human eye. The specific manifestations are blurred vision, sore eyes, severe headaches, and dizziness. This is also consistent with the subjective feelings of some users.
Because when the human brain cannot recognize visual information, the optic nerve will reversely control and adjust the lens and ciliary muscles in the eyeball to obtain clear images.
The whole process is similar to the focusing process in the professional camera mode of mobile phones. By finding a suitable focus point, a clear picture can be obtained.
If the mobile phone uses low-frequency PWM dimming, it will lead to unstable screen lighting also known as flickering. At this time, the human eye has to repeatedly adjust the lens and ciliary muscle to adapt to the screen.
If this exceeds the normal adjustment range, it will cause eye fatigue and reduce the adjustment ability. I feel like I can’t see things clearly.
On the contrary, High-frequency PWM dimming, because its frequency is high enough, can make the screen maintain high-frequency stable light, and the human eye does not need to adjust it repeatedly.
For example, we quantify the stroboscopic flicker of low-frequency PWM dimming and high-frequency PWM dimming, which are relatively common now, into game frame number curves, and combine the real flicker index and fluctuation depth of the corresponding models.
The results of the two are shown in the figure above. It can be seen that one curve has large fluctuations, while the other has fluctuations but can maintain a high degree of stability, which is why high-frequency PWM dimming mobile phones have better eye protection effects.
How Can DC Dimming Help With Screen Flickering Caused By Low-PWM
The more popular DC dimming is actually a dimming method that is more in line with the human eye’s intuition, but it will be affected by some objective factors in actual use, such as the light source of the screen, which cannot maintain a stable operation because the operating intensity is too low.
For example, in low brightness, mobile phones that support DC dimming may have a color cast phenomenon in the picture.
Without considering the influence of other factors, the eye protection effects of DC dimming and high-frequency PWM dimming are equivalent, and the former is slightly better, both of which are eye-friendly dimming methods.
It’s just that high-frequency PWM dimming is going to be a little bit magical in 2023.
The actual situation is that most of the new flagship E6 screens released in the past few months are low-brightness high-frequency PWM + medium-high brightness low-frequency PWM, the frequency is mostly 720Hz, and the flicker index and SVM index are both high.
In this case, it is questionable how effective the “high-frequency PWM” and “eye protection screens” that manufacturers are vigorously promoting are.
Here is Why DC Dimming Is Not Perfect For Mitigating Low-Frequency PWM
On the other hand, The high-frequency PWM that was vigorously promoted at various press conferences is made into a switch and hidden in the developer mode of Android phones which needs to be manually turned on, which means that the default is still full-brightness low-frequency PWM dimming.
On the flip side, there is a warning that when you enable high-frequency PWM dimming, you will increase power consumption. That being the case, why not implement a more power-saving DC dimming solution?
When consumers think they are using a mobile phone that supports high-frequency PWM dimming, but this function actually needs to be turned on manually, what they really use every day is low-frequency PWM dimming.
If there is a problem with eye health, who is to blame? So, I don’t think it’s a good idea to put it in developer mode.
In 2023, the good news is that more manufacturers will pay more attention to strobe than before. The bad news is that because each manufacturer has a different attitude towards strobe, the final product will also be different, the standards and related parameters are not transparent, and consumers can only know the frequency of high-frequency dimming.
High-frequency PWM dimming
High-frequency PWM dimming is a good dimming method, but how to regulate its use, the industry should establish an effective and beneficial standard for consumers.
High-frequency PWM dimming can effectively reduce the impact of strobe on human eyes and relieve visual fatigue during use.
We have been recommending mobile phones that support this feature in the shopping guide. In practice, there are still many users who are not interested in these features. I think there is no consensus on high-frequency PWM dimming like “low blue light”. Apart from the obscure concept itself, there is also a lack of recognized standard support.
How to Define Whether The Screen Protects the Eyes?
When it comes to eye protection standards, the first thing that comes to mind is the “IEEE Std-1789-2015 Standard” proposed by the Institute of Electrical and Electronics Engineers and the following picture to judge whether the mobile phone strobe meets the standard.
This standard does provide a reference for judging flicker. The problem is that there is a certain deviation between the measurement indicators such as the depth of fluctuation and flicker index and the actual situation of flicker, so it cannot be quantified well.
Therefore, the International Commission on Illumination later launched the “stroboscopic visibility” indicator specifically for stroboscopic, that is, SVM, covering a frequency of 80 to 2000 Hz.
Compared with the original standard, the duty cycle factor is taken into account, which is more in line with the actual situation of mobile phones. When the SVM is less than 1, the strobe is invisible; when the SVM is equal to 1, it is just visible, which means that it should not be used for a long time; when the SVM is greater than 1, it is visible, and the existence of the strobe can be detected even after a short period of use.
In addition to the SVM index test, TÜV Rheinland also conducts tests on eye protection indicators such as stroboscopic and blue light. As for the DisplayMate test, it is more inclined to the quality of the screen display, which is also an indicator worthy of attention.
What methods can consumers use to relieve eye fatigue?
Personally, I am an avid Samsung phone user. I started noticing disturbing eyestrain from galaxy s10. I find it difficult to stare at my phone for a long period of time without eyestrain.
Firstly, I personally suggest that you should always activate the “eye comfort shield” and “the extra dim features of Samsung flagships that supports them. If your eye strain is intense, then use the custom mode of eye comfort shield on Samsung phones.
Similar features are available for use on other smartphones by other brands. These measures alone, will reduce your eye fatigue considerably.
Secondly, One is to reduce the duration of mobile phone use and reduce the duration of eyes watching the screen;
Thirdly is to use the mobile phone in a relatively bright environment or increase the brightness of the mobile phone appropriately. Under medium and high brightness, increasing the screen brightness can alleviate the harm of stroboscopic;
Fourthly is to turn on the dark mode of the mobile phone, which can effectively reduce the impact of the strobe on human eyes.
As a last resort, if none of the above methods can relieve visual fatigue, and you can feel obvious discomfort just by looking at your phone, then I suggest you change to another phone.
Compared with the limited countermeasures available to consumers, it is obviously more pertinent for manufacturers and supply chains to solve the problem from the source.
Although eye protection is a complicated project, there are actually standards to follow from stroboscopic to other dimensions. PWM dimming should not be magical, eye protection should be a science. In this way, both consumers and manufacturers can have a win-win situation.
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