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Plasma Versus LCD Flat panel video displays are hot items in retail stores, and prices are dropping rapidly. Friends often ask me if they should buy an LCD or Plasma TV. Plasma Display Panels are heavy, which makes moving it a two-person job. Plasma’s also require more power than LCDs. Plasma displays have typically dominated the market for large screen (40-inch and up) sets, and LCD has been the technology used for smaller sizes. But that is rapidly changing, as ever-larger sizes are announced using both technologies. In the past year, prototypes have been shown as large as 80 inches for plasma and 57 inches for LCD. Widely available LCD models are currently found in the range of 15 to 46 inches, whereas many plasma models are found in 31- to 61-inch sizes. Their prices are comparable; though, for an identical size and resolution, plasmas have been slightly cheaper (but the prices are changing almost daily). Plasmas have been plagued with the possibility of burn-in, just like CRTs of yore. If you leave a static image or an image with static black bars on for a long time, the image will leave a permanent “ghost” on the screen. But plasma manufacturers claim that is less likely with the newest technology. So, which to buy? To me, the answer is plasma. Why? Three words––black, color, contrast. To explain what I mean it is helpful to understand a few things about each technology. LCD uses arrays of pixel-sized liquid crystals that become opaque to light when an electrical signal is applied to them. LCD panels require a light source behind them and color filters to generate red, green, and blue light. The major theoretical problem with LCD technology is that blocking light transmission is not 100 percent perfect. And transmission of light through filters results in a reduction in light intensity. Both of these limitations are being overcome by advances in LCD production, but they are still fundamental to the technology. Plasma uses electrical discharge to ionize gases, creating a “plasma” in pixel-sized cells. This ionized gas excites red, green, and blue phosphors on a closely spaced glass plate, then the phosphors emit light. In the absence of an electrical signal there is no light; in practice there is almost no light and a lot less than with an LCD in “black” condition. Thus, plasma displays have better black levels than LCDs. The colors emitted by the phosphors in a plasma display can be very intense and deeply saturated. In both these respects, plasmas are much like CRTs. They can also emit a lot of light while maintaining a constant black level, thus having excellent contrast ratios, again much like CRTs. So in a nutshell, that is why aficionados of a quality video image often prefer plasma. Bill Cruce, Widescreen Review, March 2005
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