Originally posted by: HappyPuppy
I didn't think refresh rates were changeable on an LCD.
Mebbe I be wrongful.
Why LCD screens do not cause eyestrain due to flicker.
CRT's use phosphor to create light by being excited by the electron beam. After the phosphor is excited, it begins to decay (lose light output). The electron beam needs to return to the phosphor in a specific amount of time (13.33ms for 75Hz) to keep the phosphor from decaying to the point that the human eye can perceive it. The fact that it relies on the human eye is why refresh rate/flicker is such a subjective measure. Each user will be able to perceive the Flicker differently due to their eye's ability to detect the loss of light.
LCD's do not use phosphor, but use a backlight, which is at a constant level. The image that the users eye sees is created by controlling the LCD material at each pixel. Since this is a fixed pixel display each pixel is controlled by a transistor that holds its state until told to change states.
So... the difference is that a CRT's phosphor decays and needs to be updated to maintain the light level, where a LCD does not decay and only changes light output levels when instructed to do so by the graphics board