A refresh rate refers to the speed at which a display is redrawn every second, and it is measured in hertz. Refresh rates have become an issue for LCD TVs, which lag behind plasma and DLP in their ability to reproduce fast motion without blurring.

The refresh rate for a normal LCD TV is 60 Hz, which means 60 frames per second. That’s pretty fast, but not fast enough for some action, which still causes a blur. “LCDs with the fastest response times [like 5 milliseconds] still have perceived motion blur because of the sample-and-hold drive techniques [of LCD],” says Patrick Dunn, director of display technology at THX. “However, moving to 120 Hz cuts the wait time in half between frames, because you are driving it twice as fast.”

Refresh rates are especially important with the advent of high-def DVD formats HD DVD and Blu-ray Disc, which are transferred to video in their native 24 frame-per-second rate. Some higher-end TVs today can accept a signal at 24p, as it is called, thereby eliminating the complicated process called 3:2 pulldown that is required to convert the 24 frames per second of film to 30 and 60 frames per second.

Video purists love 24p, but most of us won’t be able to see the difference. And 24p goes much more nicely into 120 Hertz (5:5 pulldown), though few TVs with 120 Hz are capable of 5:5 at this time. Most were doing the 3:2 processing to 60 Hz, then doubling that to 120 Hz. Expect to see more of this 5:5 processing as the technology evolves.