The recommended brightness level is approximately 120 cd/m2 in a bright room without direct sunbeams coming in. Brightness is typically measured in cd/m2 and the brightest monitors hit around 450-500 cd/m2 but this is not necessarily an advantage because no one can sit in front of a monitor this bright. The most common scenario is that you buy a new monitor that is far too bright out-of-the-box and reduce brightness to maybe 20-30 %. The problem occurs if the blinking/flickering is indirectly perceptible by the human eye when the PWM is running at too low frequencies.
The problem is the way PWM has been implemented in modern LCD monitors with LEDs, as it can cause eyestrainPWM is not the actual problem. Notice the significant light fluctuations. How PWM works on a LCD monitor with CCFL and on a LCD monitor with LED. But, as you can see, it also has drawbacks. It is a cheap and effective way of controlling the light output of a LCD monitor with LEDs as it gives a huge span of brightness levels. PWM (Pulse Width Modulation)The method of introducing "breaks" to reduce the brightness level is called PWM (pulse width modulation). The rest experience either mild discomfort or no discomfort at all. Studies have shown that approximately 10 % of people experience discomfort. Those who are affected never see the actual flicker it is “indirect”. Notice: We need to emphasize that all eyes are different. The use of LED obviously has numerous benefits, including much lower power consumption, far fewer toxic substances and some obvious picture quality advantages but here we are only focusing on the potential eyestrain issues as it is a separate issue that can be avoided on new monitors and even reduced on the monitor you own right now.
Thus a greater risk of experiencing eyestrain, tired eyes or in the worst-case scenario headache when working in front of a LED based monitor. Therefore, the breaks when using CCFLs are much easier on the eyes than when using LEDs. This happens with CCFL based backlight units and LED based backlight units but CCFLs have a much longer afterglow than LEDs that basically turn off instantly. When reducing the brightness setting in the menu further the breaks become longer, basically. This is done by inserting small “breaks” – or pauses – in which the LEDs turn off for a very short time. If you reduce the brightness setting in the menu to, for example, 50 % the LEDs need to omit less light.
When a monitor is set to maximum brightness the LEDs are typically glowing at full strength: 100 %.
The important aspect here is the actual method used to reduce brightness on a monitor with LED. Whether it is the one or other is irrelevant. Some monitors adjust automatically based on surroundings but often you have to do it manually. In a brightly lit room a higher monitor brightness level is preferable and in a dimly lit room, for example a cellar or studio, a much dimmer monitor is preferable. If you are unsure check the model number on the backside and Google it.Īs you might have noticed you can adjust the backlight on pretty much any monitor today via the buttons on the front. If you have a thin monitor then you have a LCD monitor with LED. LCD monitors started out by using CCFL (cold cathode fluorescent lamps) as a backlight source but in recent years manufacturers have shifted to LEDs (light emitting diodes).
It is an “invisible” flicker effect that can affect your experience in front of the monitorModern PC LCD monitors are not flicker-free but in order to understand why we need to include a short introduction.