Does the refresh rate affect LCD screens?

Question

I have never really paid any attention to the refresh rate setting on computers with LCD screens. I thought with LCD displays the pixels are either on or off, they don't flicker like in old CRT monitors.

Seems trivial to me, but my own graphics card allows me to select 59Hz or 60Hz - which leads me onto my question:

Does the refresh rate affect LCD screens? Technical info to back up any answers would be great.

Answer 1

Yes, but it is worthwhile clarifying.

LCD pixels get turned on by current and turned off then the current stops. On the other hand CRT pixels get excited when the electron beam hits them and immediate start to fade.

The implications of this are:

• With a too low refresh rate, a CRT appears to flicker as the brain has time to notice that it went dark. This depends on the individual and which part of the eye sees it since our peripheral vision is more sensitive to light.
• An LCD does not appear to flicker because pixels do not go dark between refreshes. They simply transition from one state to the next.
• The refresh rate of both CRTs and LCDs affect how they render motion. Higher refreshes give smoother motion.
• LCDs have an upper limit on the refresh rate due to the time it takes for a pixel to change state. This is known as response time. If the refresh rate is too fast, then some pixels do not have enough time to change and this results in ghosting.
• Is it possible on a CRT to have ghosting as well but only at very high refresh rates since phosphors fade quite fast.
• LCDs do not have lower limits to their refresh rates. I once tested a display with 3830x2400 resolution and the first version has a 24 Hz rate. No flicker was noticeable. It was then upgraded to 48 Hz and the discontinued sadly, guess not enough people paid the 27K price tag!

Answer 2

Yes. But since it takes longer for a LCD cell to depolarize than for a CRT phosphor to extinguish, it doesn't affect them very much.