OTHER TECH

To preserve contrast and sharpness as much as possible, active-matrix LCDs use tiny switches called thin-film transistors (TFTs) that allow the control circuit to address each subpixel individually without affecting the others, untwisting it in tiny degrees to produce the slight gradations in intensity necessary to create a realistic image. Typical active LCDs are capable of showing 16.8 million colors, created by 256 gradations in each of the three primary colors.

A typical 1,024 x 768-pixel LCD panel (found in direct-view TV sets and computer monitors) or chip (found inside front projectors and RPTVs) has around 2.3 million individual TFTs, representing quite a manufacturing feat. A problem with any one of these TFTs causes a "bad pixel," which can show up as a spot whose intensity doesn't change or changes differently from the rest of the display. Even modern LCDs have bad pixels, but advances in manufacturing and quality control have made them rare.

LCD in the Living Room For home entertainment, LCDs have been most popular in front-projection installations, since they are less expensive than CRT projectors and far easier to set up. An LCD front projector contains a lamp that shines through the small LCD chip and then the lens, which throws an enlarged image onto the screen. Better versions contain three separate chips devoted to red, green, and blue (like the three tubes in a CRT projector), doing away with the subpixel arrangement.

The LCD projectors found in corporate boardrooms and video art galleries aren't really the best choice for people building big-screen home theater systems. They're designed to be attached to computers and provide a bright PowerPoint-friendly picture even under fluorescent lighting. In a home environment, their picture quality suffers considerably compared with CRT projectors.