At present, the OLED screens on the market (including Samsung's AMOLED screens) are much more eyesore than the LCD screens with PWM dimming flash frequency exceeding 1250 Hz.
With the impact of the full screen trend, more and more mobile phone manufacturers have used OLED screens for their flagship. Compared with LCD screen, OLED screen has many advantages: light and thin, power saving, good color, etc. However, the current OLED screen also has some defects that cannot be ignored—— Blindness and Burn the screen 。
Blindness
According to IEEE literature, Stroboscopic LED lights can cause diseases related to visual fatigue, migraine or photosensitive epilepsy.
According to IEEE PAR1789, for OLED screen mobile phones that currently use PWM dimming, the flashing frequency of PWM dimming should be at least 1250 Hz Above, the flashing frequency of PWM dimming that will not affect human health basically should be Above 3000 Hz!
Even Samsung Super AMOLED, the best OLED screen on mobile phones at present, has a PWM dimming flash frequency of only about 215 Hz - 250 Hz, which is far below the healthy allowable range value described in IEEE literature.
In addition to the stroboscopic frequency lower than the health allowable value, the OLED screen also has a parameter that can intuitively understand the harm of the impact on people
Stroboscopic index
Strobe index=(maximum brightness current brightness)/maximum brightness
In brief, for the Super AMOLED screen with a PWM dimming flash frequency of 240 Hz, the recommended health value should be 0.24.
Calculate the current iPhone X: The maximum brightness of the full screen of iPhone X is 580 nits, and the brightness should not be lower than 440 nits in terms of strobe alone.
The recommended value of screen brightness for mobile phones generally used indoors in the daytime is 100 nits - 200 nits The brightness of healthy use at night is also lower. Xiaomi even promoted the ultra dark night light screen with 1 nit brightness on Xiaomi 6.
In other words, whenever you use an AMOLED screen phone indoors, Either the eye is injured by high brightness, or the eye is injured by stroboscopic.
Look at the moving picture below to see what stroboscopic is like. As the brightness of the iPhone X screen changes, PWM control will also change.
Although the camera can capture stroboscopic, it does not mean that the eyes can feel stroboscopic, Because some people are sensitive to stroboscopic, and some people are not so sensitive, there are still individual differences in stroboscopic.
Burn screen
After "blind", let's take a look at the burning screen.
Why does the OLED screen burn?
Because of the display principle of OLED screens (including Samsung AMOLED screens), each pixel of OLED screens can self emit light. However, because different pixels emit light at different times, the attenuation speed of each pixel is different, which is what we call "burning the screen".
But in general, it is difficult to burn the OLED screen in the following picture! Because according to the previous Cetizen screen burning test, the iPhone X screen burning to this extent will appear 510 hours after the same picture is lit!
For ordinary users, the maximum screen brightness will not be turned on and the same screen will be displayed for more than 510 hours, so it is difficult to burn the screen in general.
However, this does not mean that the OLED screen will not burn at all, Even for the expensive iPhone X, Apple cannot guarantee that it will not burn the screen at all.
And in Apple's official view, The burning screen of iPhone X is not a fault but a normal performance.
In general, due to the limitations of current hardware conditions, the burning of OLED screens is an unavoidable problem, However, if you pay attention to the usage habits, screen burning can be greatly reduced or even will not occur. And the sensory problems of stroboscopic also vary from person to person. If you have used the OLED screen without feeling any discomfort to your eyes, you can continue to use it with confidence.
LCD screen is not completely risk free
But if you think there is no risk of stroboscopic when using LCD screen, you are still too young.
In fact, the LCD screen can also be dimmed with PWM, and even the time for large-scale dimming of LCD screen with PWM is earlier than OLED. From 2011 to 2014, in response to the national "call for energy conservation and emission reduction", From CCFL (cold cathode fluorescent lamp) to LED backlight, most manufacturers choose the "PWM dimming" with lower cost and easier quality control.
Later, many users found that the new monitor was more eyesore than the old one. At that time, the resistance of manufacturers was no less than that of the current civil "anti OLED alliance". Later, many manufacturers began to promote "no flash screen".
Up to now, LCD screens on desktops and mobile phones rarely use PWM dimming. However, the beggar version of Microsoft Surface Pro 4 a few years ago actually used PWM dimming (no other version, really core M has no human rights).
via：
IEEE PAR1789； GB/T 31831-2015； GB/T 9473-2017； PWM Ranking - The Best Displays for the Eyes； Cetizen； Magician Dan Xiaoding; Zhihu Chen Jing
Do you think there is a difference between these two screens?
