History
HDTVs had been in development for years, but disputes between manufacturers held progress back until the FCC-mandated National Television Systems Committee (NTSC) created the standard for analog signals and later the Advanced Television Systems Committee (ATSC) determined the standard for digital signals. It took more time for stations to start broadcasting digitally and in HD, and for HDTVs to become less costly to catch on in the marketplace.
By 2009, with the United States switching to digital-only broadcasts, HDTVs have become much more affordable and popular in American homes.
Specifications
HDTV monitors have a much greater picture resolution than older analog televisions, with 1280 (horizontal) by 720 (vertical) or 1920 by 1080 lines of resolution, much higher than the 720 by 480 lines of standard definition TVs. This, along with a higher frame rate of up to 25 frames per second, gives HD the sharper, more detailed pictures. And, where older TVs had an aspect ratio of 4:3, HDTVs have an aspect ratio of 16:9, similar to a movie theater screen. Still, even with an HDTV, the picture can only have HD quality if it comes from a digital HD over-the-air signal or an HD channel from a digital cable or satellite provider.
LCD vs. Plasma HDTVs
With LCD screens, thousands of pixels are in front of a fluorescent backlight. Within each pixel are three subpixels consisting of red, blue and green cells. When light hits the pixels, an electric current determines the color and the variations within the pixels creates the picture you see. Plasma screens consist of two thin screens of glass, with cells in between holding an inert mixture of gases, creating the plasma. The plasma excites a series of red, blue and green phosphors to emit light, which creates the image. As of now, plasma TVs can be made slightly larger than LCD, while LCD screens can be slightly thinner. One potential drawback of plasma TVs is that if the image stays motionless too long, it can create a permanent "burn in" after-image on the screen. On average, LCDs use half the power of Plasma TVs. Still, both still represent a huge upgrade from older standard-definition TVs.
Tags: aspect ratio, blue green, from digital, HDTVs have, Systems Committee, Television Systems
