The Only Guide you need to Learn about HDTV
High-Definition Television, or HDTV, is the highest form of digital television (DTV). We’re in the midst of a national transition to this new form of televised home entertainment - and for good reason. In the 1980s, at the urging of broadcasters, the Federal Communications Commission began to explore ways in which to transition from fuzzy old analog TV to crystal clear HDTV. In the ’90s, led by pioneering technology developments at U.S. companies (including LG’s Zenith Subsidiary), and due to the many efficiencies of digital, the FCC decided to take the 50-year-old television system from analog to digital.
Important Things to Know
- High-Definition TVs can be standard shaped direct-view tubes, LCDs, Plasma monitors, rear-projection units or front Projection systems that require separate screens. High Definition refers to resolution (the horizontal lines that can be displayed on the screen), not the screen technology upon which the TV is based
- Virtually all TV stations are now broadcasting digitally, and analog broadcasts are expected to end in early 2009. Manufacturers and service providers will manufacture reasonably priced converters to down-convert digital signals to analog, so that your current analog TV will continue to receive over-the-air signals when analog ends. But when you upgrade your TV to a DTV, you will get all the great benefits of digital broadcasts, theater sound and additional future digital services.
- Digital Cable is generally not HDTV. This is a common misconception. Digital Cable is usually analog grade TV that is digitized and sent over the cable as a digital signal. The video and picture quality may be superior to standard analog cable, but is much lower than High-Definition. That being said, some cable systems also offer several HDTV channels that you can receive, some times directly with any DTV receiver, or with a special set-top box or CableCARD® (CableCARD is a technology built in a TV so that you can access scrambled and subscription programming without the dreaded cable box) provided by the cable operator.
- There are already lots of HDTV programs available: movies to documentaries, and sports to sitcoms. Programming is available from local broadcasters, cable providers, and satellite providers. There is currently at least 200 hours of HDTV available per week, including 70 hours of free, over-the-air programming from the major networks, and new HDTV programming is being added all the time.
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Resolutions
Under the ATSC system, broadcasters can broadcast in any resolution they desire. But, to ensure that consumer televisions will receive broadcast signals, broadcasters have standardized their broadcasts, and consumer televisions have also standardized, so that the broadcast resolution (amount of picture detail) falls into three categories or formats. Standard definition, with the same resolution as today’s analog signals (but with digital, there is no interference - the picture is perfect), Enhanced definition, with the same resolution as today’s DVD players, and High Definition (HD), which has about six times the resolution of standard definition.
Standard definition signals are 4:3 or “standard” shaped. Enhanced definition and high definition signals are “widescreen” (16:9 aspect ratio). HD is broadcast in two signal formats - 720p x 1280 or 1080i x 1920. One is interlaced, and one is progressive. Most humans cannot see any difference between 720p and 1080i.
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LCD Vs. PLASMA
LCD
LCD flat panel televisions come in a variety of sizes. They’re just a few inches deep, relatively lightweight and can be also be used as a television or computer monitor.
LCD flat panels are digital televisions with a fixed pixel structure. Each pixel has three sub-pixels of red, green and blue. The image of a flat panel LCD display is generated by a backlight behind the panel. The image goes through a polarizing filter. Each sub-pixel has tiny crystals that create different levels of brightness.
LCDs are available in a wide range of screen sizes starting at 15 inches and going up to 55 inches. The small screens are offered in both 4:3 and widescreen versions. Screens above 22 inches are strictly widescreen models. You may choose either enhanced definition (ED) or high-definition (HD) LCD televisions.
The 4:3 ED models have a resolution matrix of 640 Horizontal x 480 Vertical. The widescreen version is 852 H x 480 V. The high-definition models come in several resolutions, depending on size. The smaller models are 1280 x 768 (15:9 aspect ratio) or 1280 x 720 (16:9). The largest LCD panels (over 42″) are 1920 X 1080 (16:9), the highest resolution standard. You should only consider a ED model if you never plan to view closer than 3.5 times the screen size.
Plasma
Some larger flat screens/panels use a conductive plasma instead of liquid crystal. These are commonly called plasma displays. Plasma displays are very sleek and thin, making them a hot choice among consumers who say this technology delivers the best color saturation, accuracy, and vibrancy.
Despite their large screen sizes, plasma screens are ultra-slim. The least expensive plasmas are usually EDTV (480p). Plasma screens have a bright picture with excellent off-axis viewing angles. They have better contrast than LCD TVs, though not usually as good as CRT.
Gas in the plasma state reacts with phosphors in each sub-pixel to produce what engineers call “colored light”. That explains why a plasma TV has such vivid colors and such a clear picture.
[ via LG ]
