Sometimes you experience eye strain, headache, for too long looking at an OLED screen, possibly due to something called Pulse Width Modulation (PWM). This article will help you better understand it.
OLED technology is widely used on smartphones for many advantages, such as dramatic contrast, deep blacks, thinner and lighter LCDs. However, OLED screen phones are using the method of reducing screen brightness as Pulse Width Modulation (PWM).
This is different from LCD screens that use DC dimming, and it makes some users feel uncomfortable. So how are they different? Why is PWM annoying a small group of us and DC dimming is not?
How does PWM work?
This technology simply means changing the width of the light pulses, thereby increasing or decreasing the screen brightness. The frequency of light pulses is often very high – 200Hz and above – making it impossible for the human eye to recognize each individual pulse. Therefore, we will receive the average amount of light that these pulses emit.
The state of the screen turned off or on is actually determined by the amount of light it receives. When you reduce the screen brightness, in fact, the off state lasts longer than it turns on, the amount of light generated by the pulses decreases so we think that the screen is darkened.
At 100% brightness, you notice it’s always bright because the pulse is at its widest. When reduced to 50%, the panel emits shorter pulses, divided into intervals that reduce the amount of light received. And if you continue to lower the brightness, the pulse amplitude will be shorter, the screen stays longer. At extremely low brightness levels, the spacing between the pulses is large enough for them to be discrete and visible to the human eye. At this time, flicker occurs.
Most people are not sensitive enough to recognize this screen flicker. Only a small group felt uncomfortable, although they did not know where the cause was. With this group, flicker for a long time makes the eyes faster tired, headache or migraine. Especially with the habit of using an OLED screen smartphone in low light conditions, or at times when the eyes should rest – for example, before going to sleep – is not as good.