Thin Is In When It Comes to HDTV Displays - dummies

Thin Is In When It Comes to HDTV Displays

By Danny Briere, Pat Hurley

Flat-panel TV technology — super-thin HDTVs that you can hang on the wall like a painting — have really taken off in popularity. A big-screen, flat-panel plasma or LCD TV has become the status symbol almost everywhere. There’s good reason for this mania — flat panels provide a large viewing area with almost no intrusion into your HDTV viewing room, and they can offer a very high-quality HDTV picture, as well.

Loving your LCD

If you have a flat-panel display for your PC, a laptop PC, a PDA, a cell phone, a Game Boy — or just about any digital device with a display, you have an LCD display. LCDs have been around for decades, mainly in lower-resolution formats and smaller sizes (such as phone screens), but they are getting larger all the time — and growing sharper in resolution.

The LCDs being discussed are direct view LCDs — in other words, LCD HDTVs where you look at the LCD display itself. In contrast, projectors with LCD microdisplays have teeny tiny LCDs that are used to project a bigger image on a screen.

Even as they get bigger, however, LCDs tend to be the smallest HDTVs available on the market (so they may not be big enough for a true home-theater environment). Most LCD HDTVs on the market are smaller than 30 or 32 inches — smaller, in other words, than projectors or plasmas, and smaller than many tube-based CRT HDTVs.

However, advances in LCD manufacturing, as well as new technologies, such as O-LED (Organic LED) and SED (Surface-conduction Electron-emitter Displays), promise LCD-like displays in ever-bigger sizes in the future. In addition to the “super-skinny-hang-it-on-the-wall” attribute, here are other reasons LCD displays are so appealing:

  • Excellent color: LCDs can display millions of colors, and do so accurately (meaning the color coming off the screen is faithful to the color in your broadcast or recording).
  • PC-monitor-capable: Many LCD HDTVs can also be used as big (huge!) PC monitors. This trick is especially cool if you have one of those neat Media Center PCs.
  • No burn-in: HDTVs that rely upon phosphors, such as CRTs and plasmas, can, under certain circumstances, experience burn-in, where ghost images are permanently burned into the screen. LCDs are immune from this phenomenon.

Besides a size limitation, consider a few other issues before you choose an LCD HDTV:

  • Limited viewing angle: LCDs typically have a poor viewing angle — the angle you can sit away from perpendicular and still see a clear image on-screen. Manufacturers have been working diligently to improve this characteristic (with some success). Check the specs before you buy — most LCD HDTVs will have viewing angles listed in their specifications.
  • Slow pixel response time: Another area that LCD HDTV makers are working overtime to improve is the pixel response time of their TVs. Basically, the individual pixels within an LCD HDTV take a slight amount of time to change color and intensity. For really fast-moving video content (particularly in a 720p picture, where every pixel can change as many as 60 times per second), an LCD TV can end up with some artifacts (visible flaws) where the picture from a previous frame is still slightly visible on-screen as the new one is being drawn. Typically, this isn’t a huge and noticeable deal, but it’s not beyond the realm of possibility that you might notice it.
  • Limited brightness: The LCD is a transmissive system — light is shined through the liquid crystals — some of that light gets absorbed or reflected back away from the viewer. This means that LCD displays are not as bright as CRT, plasma and even some projection TVs (DLP, for example) — this could be a factor in a brightly lit room.

Everyone’s crazy about plasma

The really hot spot in the HDTV technology market is the plasma TV. Plasma TVs combine a thin, compact chassis with a truly large (even huge) screen size, and then add beautiful high-definition pictures to the mix. For many potential HDTV buyers, plasmas really fit the bill.

A plasma screen contains literally millions of gas-filled cells (each one acting as a single image pixel) trapped between two pieces of glass. An electrical grid zaps these cells and causes the gases to ionize (and ionized gas is plasma — hence the name). The ionized gases, in turn, cause a layer of phosphor on the viewer’s side layer of glass to light up (just as the electron gun in a CRT causes the phosphor to light up on the front of the tube).

Despite their compact dimensions (in the “depth” direction at least — many plasmas are only about 4 inches deep), plasma HDTVs are available in 42-, 50-, and even 60-plus-inch sizes. Imagine a 4- or 5-inch-deep HDTV that spans 5 feet diagonally, and you can see the instant appeal of plasma.

Other benefits of plasma displays include:

  • Excellent brightness: Plasma HDTVs are second only to CRT direct-view TVs in terms of picture brightness — plasmas don’t rely on a light bulb shining through or reflecting off of something. In some ways, plasma brightness is even better than CRT’s because the picture is uncannily evenly bright across the entire screen. In a CRT, there always is some difference in brightness as the electron beam reaches different parts of the screen.
  • High resolution: HDTV plasma TVs can often reach higher horizontal resolutions that CRT-based direct-view sets just can’t match. The finest plasma TVs have such high resolutions (and such smooth images) that they look like nothing more than beautiful film images.
  • Progressive by nature: Like LCD displays, plasma systems don’t use a scanning electron beam to create a picture. Instead, all the pixels on the screen are lit up simultaneously. Progressive HDTV sources (such as 720p) and non-HDTV sources (such as progressive-scan DVD players) are displayed to full advantage on a plasma HDTV.
  • A wide viewing angle: Plasma displays have a good picture even when you’re sitting “off axis” (not perpendicular to the screen surface). This is a huge benefit for smaller rooms, where viewers may sit relatively far off to the sides of the screen, at wider angles.

Plasma’s not perfect, of course:

  • Susceptible to burn-in: Any system that uses a phosphor screen to display video can fall victim to the phosphor burn-in mentioned earlier in this chapter. If the Xbox is a primary HDTV source in your home, consider something besides a plasma — maybe an LCD HDTV or a rear-projection microdisplay HDTV.
    You can minimize burn-in on any display by calibrating the set properly and reducing the brightness from its (usually too-high) factory setting.
  • Shorter life span: Another phenomenon of any phosphor-based display system is that eventually the phosphors “wear out” or lose their brightness. This is a subtle and slow process, but it inevitably happens. If you’ve saved up to buy an HDTV to last you a lifetime, well, don’t get a plasma unless your personal actuary tells you that you’re close to the end of your rope.
  • Less-than-perfect color reproduction: Although plasma displays are capable of producing a breathtaking array of colors, all the sets built to date have had an unfortunate tendency to make red colors look more orange than true red.