Almost all LCD owners will notice some degree of clouding effect on their HDTVs during dark or completely black scenes. What is the clouding effect? It’s a varying degree of brightness visible across the screen. HDTV reviewers tend to describe the clouding effect as “poor screen uniformity.” It can be caused by different sources, most often from uneven backlighting or flaws in the LCD’s matrix of thin-film transistors. Clouding is most noticeable when a single dark color is shown on the screen, eg, black or dark blue. Other terms for the effect are backlight bleed, flashlight effect, cloud effect, and mura or the mura effect. Mura is a Japanese word meaning an unevenness, blemish, or inconsistency. The clouding effect is generally limited to LCDs because plasmas have a different back light technology.
One way to combat this effect is to avoid watching your television in completely dark rooms. Turn on a lamp with a low light setting to keep a small amount of ambient light in the room. Some LCD manufacters offer ambient light built in to their television, most notably Philips Ambilight.