This, is a really important point. LCDs are NOT CRTs. So it isn't that the top left pixel of the screen is getting dimmer and dimmer while the CRT is painting lower pixels, on an LCD it is simply not changing.
What "30Hz" means in LCD terms is that if you go to change a pixel, the fastest you can do that is once every 33 mS but during the whole time it isn't changed, it stays the same intensity.
What "30Hz" means in LCD terms is that if you go to change a pixel, the fastest you can do that is once every 33 mS but during the whole time it isn't changed, it stays the same intensity.