We spend a lot of time looking at monitors. That’s why we want to make sure that they’re as easy on the eyes as can be. One issue that some monitors can have is flicker, or extremely rapid cycling of light. This can be visible or invisible but even the invisible kind can be tiring on your eyes. Flicker can be caused by a number of things. For older monitors, the likely culprit is PWM, or pulse width modulation. To reduce the screen’s brightness, PWM turns the monitor’s backlight off and on at a very high rate. This can cause eye strain over long periods of viewing. Thankfully, most modern monitors—including HP monitors—are what is called Flicker-Free, meaning they employ DC (or direct current) modulation to maintain brightness at a constant level.