LCD panels are sleek, sexy, and versatile. Now several vendors offer multifunction LCD flat-panel monitors that provide both PC and TV functions in one, but will they replace your 27-inch living room TV anytime soon?
For most consumers, LCD TVs will best function as a flat-panel PC display first and a TV second. If you live in a small apartment or have a home office, an LCD Television can save space and be cost effective. If you're thinking about spending a small fortune on one, there are several things to take into consideration.
Features galore All LCD TVs offer progressive scan support and pleasingly flat screens by design. They also provide users with a bevy of input options, adding to their versatility. Most LCD displays double as computer monitors by allowing standard analog VGA (PC) input, a great option if you need your display to pull double duty as a PC monitor to save money and space. Nearly all flat panel LCD Televisions offer the option to mount on a wall or under a cabinet.
While many support "HDTV compatibility" and "progressive scan" as features prominently displayed on the box, don't forget that 99 percent of regular NTSC TV broadcasts and the typical DVD player won't let you take advantage of these features.
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What is LCD Technology and how does it work?
LCD technology is based on the properties of polarized light. Two thin, polarized panels sandwich a thin liquid-crystal gel that is divided into individual pixels. An X/Y grid of wires allows each pixel in the array to be activated individually. When an LCD pixel darkens, it polarizes at 90 degrees to the sandwiching polarizing screens. This cross-polarizing blocks light from passing through the LCD screen where that pixel has darkened. The pixel darkens in proportion to the voltage applied to it: For a bright detail, a low voltage is applied to the pixel; for a dark shadow area, a higher voltage is applied. LCDs aren’t completely opaque to light, however; some light will always penetrate even the blackest LCD pixels.
That LCD pixels are incapable of blocking all light might seem a fatal flaw -- until you realize that film has the same problem. Light passes through film to make the images we see on the screen, but the blackest blacks on movie film are not entirely opaque. In movie theaters, blacks on the screen look fairly black because the image is projected to a very large size, which weakens the small amount of light that leaks through the black areas on the film. As long as you keep an LCD’s image size within the design parameters, you’ll get adequate blacks -- slightly better than plasma’s, and comparable to DLP’s, but not quite as good as CRT’s. A CRT’s advantage is that the phosphors on the tube are "off" when the pixel is supposed to be black -- no light at all reaches the screen for that pixel.
The resolution of almost any current LCD display, regardless of size, is either 1280x768 or 1280x720 -- about the same as current DLP displays. This makes LCD monitors capable of displaying 720p HDTV at full resolution (1280x720), but the highest HDTV resolution, 1080i (1920x1080), will have to be downsampled to match the LCD’s capabilities. During this downsampling, the interlaced 1080i input signal also must be converted to the progressive 720p format, which takes additional processing power to do correctly.
Individual LCD panels in projection products are usually in the range of 0.75" to 1.5" (diagonal) -- generally, the larger the final image, the larger the panels. While the panel may be larger, it doesn’t contain more pixels. Still, larger panels pass more light per unit area, which makes for a larger, brighter picture.
Being fixed-pixel devices, like plasma and DLP displays, LCDs require manipulation of every video source signal in order for these signals to be displayed at the panel’s "native" resolution of 1280x768 or 1280x720. Lower resolutions from cable, satellite, DVDs, VCRs, and camcorders must be upsampled to the native resolution; the highest-resolution HDTV images must be downsampled. As with plasma and DLP devices, the quality of the scaling has a direct impact on image quality. But good scaling is complex and expensive; the less expensive the product, the lower the scaling budget.
How It Works
Whether spread across a flat-panel screen or placed in the heart of a projector, all LCDs are pretty much the same. A matrix of thin-film transistors (TFTs) supplies voltage to liquid crystal-filled cells sandwiched between two sheets of glass. As with plasma panels, a trio of red, green, and blue cells make up one pixel. When hit with an electrical charge, the crystals "untwist" to an exact degree to filter light generated by a lamp behind the screen (for flat-panel TVs) or one shining through a small LCD chip (for projection TVs).
LCD TV Life span
Life span, the number of viewing hours a television provides before dimming to half brightness, is one of the biggest advantages LCD has over plasma. Though the numbers vary among the different brands, plasma TVs offer 30,000 to 60,000 hours to half life, while LCD TVs last for up to 60,000 and possibly longer if bulb replacement is an option.
Computers and video games
Most plasma and LCD TVs can double as computer monitors; many even offer a DVI port for optimal video quality. They'll also hook up to a game console without any problems. So which technology is better for these purposes? From a performance standpoint, it's hard to pick a winner.