Happiness is 22 milliseconds away

Yesterday, I friend of mine ask me if I knew why vendor where insisting that a lower refresh rate on LCD computer monitor was a necessity. He was arguing that a 8ms refresh rate should be more then enough since the human eyes only see 24 images per second (1/24 so 1 image by 42ms). Above that, CRT monitor have typically 22-28 ms refresh rate and the image is crystal clear.

He had a good point. So I did my homework and I found the difference. Each pixel in a CRT emits most of the light in under 1ms. So if you have a 22ms monitor, each pixel need 23 ms (22ms refresh rate + 1ms to emit the light) to change state. In a LCD, will emits light for a much longer type … nearly 20ms. So if you add this to the refresh rate of an old LCD (between 12 to 25) you can have a display time of 45ms … which is way over the 42ms baseline.

This explain why old LCD where kind of blurry when playing a movie. Nowadays LCD have a much better refresh rate, between 2 to 8. But again, this add up to 22ms to 28ms for a whole cycle which is more closer to the average CRT monitor.