What Is the Difference Between Plasma, LCD and LED HDTVs?by Ken Burnside
As of January 2012, nearly 70 percent of American households have an HDTV. According to Lechtman Research Group, this is a four-fold increase over the number of houses owning one in 2006. These HDTVs are built around one of three competing technology bases -- plasma, LCD and LED.
What Is HDTV?
An HDTV usually has a 16:10 or 16:9 wide-screen format, like a movie theater screen. Older CRT TVs had a 3:2 aspect ratio. HDTVs run at a higher screen resolution; the older standard ran at 520 lines per screen while HDTVs have 720 and 1080 lines per screen, giving sharper, clearer images. New technology in the horizon, called 4K resolution, has 4,000 lines per screen and is due to hit the market in 2013.
The initial HDTV market was plasma technology. Plasma technology uses an ionized gas and electrical fields to change the color of each pixel and, like CRTs before it, had an unquestionable advantage when displaying fast-moving content like action movies and sports. This advantage is still present but is shrinking as LCD technology improves. TVs are self-lighting pixels, which means that when the display is showing dark colors or black, the colors are richer and the contrast ratio is better. As lower-priced LCD and LED screens have hit the market, plasma TVs have become the domain of very high-end, large-screen TVs. Plasma TVs are also the least energy efficient of any HDTV, although any HDTV will use less electricity than a comparably sized CRT display.
An LCD TV is a laptop screen enlarged. It uses a film of liquid crystals to form the image and has a compact fluorescent backlight. This backlight means there's always some light coming from the screen, which washes out blacks and dark colors. Backlights also age; it's not uncommon for one edge of the display to become noticeably brighter than the other. LCD TVs quickly came to dominate the low end of the HDTV market. They used to have problems with ghosting brought on by slow response times, but now LCD TVs have a fast enough response time that ghosting and screen artifacts, like smearing comet-tails after sporting figures, are a thing of the past.
An LED TV is an LCD TV with an array of pinhole-sized light emitting diodes behind the display. Depending on the manufacturer, each pixel may have anywhere from one to nine unique LEDs behind it, and each one can have its brightness adjusted individually. This allows the same digital signal processor that sends the image to the pixel to adjust the brightness of the pixel to match what's intended for the media being played. Based on the high-end televisions offered by major manufacturers, LED TVs appear to be the technology that's winning the HDTV wars in the marketplace.
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