Today’s HDTV landscape is bustling with choices that go well beyond simply choosing how big a screen you want. To help narrow the field, we suggest starting with Display Types and Display Technologies to figure out what kind of TV will best suit your lifestyle — and budget.
Understanding the TechnologyIt’s easy to get inundated with buzzwords, acronyms, and abbreviations. We help you sort them out.
Display Types Direct-view CRT | Rear projection | Flat Panels | Front projection
Display Technologies CRT | Plasma | DLP | LCD | LCoS
Resolution: What's HDTV and What Isn't
Aspect Ratio: Widescreen vs. Standard
Color Temperature
Screen Size
Contrast Ratio
Interlacing, Deinterlacing, and Scaling
Understanding Our Lab Data
Shopping Tips
Before heading for the stores with your wish list in hand, here are some fundamentals to keep in mind.
Setup
Everything you need to know to get your new high-def set hooked up right and looking great
How to Set Up Your HDTV
Connections
Getting High-Def Shows
More Information
Visit the HDTV Info Center for more ideas, information, and reviews on the latest in HDTV technology.
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Shopping Tips Stick with Reputable Brands and Retailers Consider Spending a Little More than You’d Planned Bring Demo Discs You Know and Love If Possible, Optimize Each Set’s Picture Before Evaluation Take Your Time Don’t Neglect the Boring Details |
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Shopping Tips Stick with Reputable Brands and Retailers Consider Spending a Little More than You’d Planned Bring Demo Discs You Know and Love If Possible, Optimize Each Set’s Picture Before Evaluation Take Your Time Don’t Neglect the Boring Details |
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Display Types Direct-view CRT | Rear projection | Flat Panels | Front projection | Back to HDTV Overview Direct-view CRT (cathode-ray tube)Tube TVs have been around for decades, and though they’re slowly going away as big-name brands focus on new technologies, the best of the breed can still deliver superb pictures. And they’re affordable ($1,000 or less, with come sets available for as little as $500 or $600). But the screens on direct-view models are relatively small — 34 inches at the most nowadays — and their cabinets are bulky and very heavy. (They’re called “direct-view” because you look right at the tube, unlike rear-projection CRT TVs, in which the beams from separate red, green, and blue tubes combine to form a full-color image on the screen.) Rear Projection (RPTV) Flat Panels Front Projection |
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Display Technologies CRT | Plasma | DLP | LCD | LCoS | Back to HDTV Overview CRTCathode-ray tube technology was used in the very first TVs, and after all these years, it’s still a common and inexpensive way to get a video image into your home. Direct-view CRTs are the familiar glass-fronted TV sets, which have evolved to include flat-glass and widescreen varieties. Rear- and front-projection CRTs use three tubes side by side (one each for red, green, and blue) to create an image that’s then sprayed onto a large screen. How It Works — A direct-view tube contains a “gun” consisting of a cathode that emits three distinct invisible electron beams and anodes that accelerate them. The beams are aimed at red, green, and blue phosphors set into the screen, which glow to produce the picture. (A metal grid on the tube’s inside face, called a shadow mask, helps keep the beams on target.) Combining the three primary colors in varying proportions produces the full color range. In the three-tube designs used in big-screen projection TVs, each tube fires at its own small screen coated with a single phosphor color. Lenses and mirrors focus the colored images onto the viewing screen. The tubes must be perfectly aligned (“converged”), or else distortions such as red or blue fringes around objects will appear. Pros
•Less expensive than competing technologies (except for front projection). •Reliable. Direct-view tubes last ten years or longer with little or no maintenance. •Very good picture quality, though the technology no longer has the commanding edge it once enjoyed over others with respect to reproduction of deep black and shadow detail. Cons •Big and heavy. •Direct-view screen sizes top out at 36 inches. •Susceptible to burn-in, and CRT projection sets are subject to convergence errors as well. They don’t do as well as the other technologies with ambient room light and produce images that usually look less sharp — although with careful adjustment a CRT projection set can look just as sharp as a flat-panel TV. Where It’s At — Having graced American living rooms for the past half-century, direct-view sets are fading fast in popularity, especially in the high-end market. Big-screen projection CRTs have largely been overtaken by lighter, shallower TVs based on other technologies. Plasma How It Works — Each pixel in a plasma display consists of three gas-filled sub-pixels (cells) coated with red, green, or blue phosphor. Electrodes above and below the cells (the top electrode layer is transparent) jolt them with varying amounts of voltage. This excites the gas in the cells to a plasma state, stimulating the phosphors to produce colored light. Pros
•Uniformly bright picture over a wide viewing angle — even in a brightly lit room. •Svelte design and large screen size. •Wide 16:9 aspect ratio screen and on nearly all current models enough pixels for HDTV resolution. Cons •Can be expensive, especially for screens larger than 50 inches. •On some sets, the black parts of the picture, such as dark shadows or letterbox bars on widescreen movies, look dark gray instead of black. (The best models now do pretty well, however.) •Subject to burn-in, where an image becomes permanently etched onto the screen. But this won’t happen unless you leave a bright stationary image on the screen for hours at a time. Recent models have burn-in prevention features, such as “pixel orbiters,” which exercise pixels by slowly shifting an image around the display. Where It’s At — Plasmas are available from many manufacturers, with 42-inch high-definition models available for as little as $1,200 and 50-inch displays starting at about $1,800. Expect to pay more for top performance, cutting edge features (such as 1080p resolution), or a really huge screen, however. DLP How It Works — High-def DLP TVs use a 16:9 chip, called a Digital Micromirror Device (DMD), packed with a million or more individually hinged and controlled “micromirrors” that pivot to reflect light from a lamp through a lens onto a screen. DLP sets fall mainly into two camps. Single-chip RPTVs and front projectors filter white light from the lamp through a rapidly spinning color wheel to produce color, while the more expensive ($15,000 and up) three-chip front projectors dedicate one chip each to red, green, and blue. (Some single-chip DLP rear-projectors now use high-intensity color LEDs instead of a white lamp, eliminating the need for a color wheel.) Pros
•Though it still can’t yet reproduce dark scenes quite as well as the best CRTs can, DLP can now come very close. DLP sets typically achieve deeper, more realistic shadows and blacks than LCD models and are comparable to plasmas and LCoS displays in this characteristic. •Because the DMD mirrors are so close together, DLP sets normally don’t have a problem with the “screen door” effect (a faint image of the pixel grid) that was especially noticeable with early LCD projectors. •No danger of screen burn-in. •DLP front projectors can cost much less than comparable CRT models, while DLP rear-projection TVs now challenge CRT models in price and are much slimmer and lighter. Cons •DLP rear-projection TVs are somewhat more expensive than the same-size CRT sets. •A small percentage of people occasionally see “rainbows” in images produced by single-chip DLP projectors with color wheels: fleeting separations of the three primary colors into narrow streaks at the edges of moving objects. Incidence of this effect has been dramatically reduced as projectors have moved from the three- and four-segment color wheels of early designs to faster-spinning six-, seven-, and eight-segment wheels, however, and it is completely eliminated in models that use LED or laser light sources instead of conventional white lamps. Where It’s At — Many manufacturers offer DLP RPTVs, with prices starting at about $1,500. And don’t rule out DLP front projectors. Basic models start at around $700, while HDTV-ready models go from about $1,000 up. LCD How It Works — A matrix of thin-film transistors (TFTs) supplies voltage to liquid crystal-filled cells sandwiched between two sheets of glass. As with plasma panels, a trio of red, green, and blue cells make up one pixel. When hit with an electrical charge, the crystals “untwist,” allowing light generated by a lamp behind the screen (for flat-panel TVs) or a lamp shining through a small LCD chip (for projection TVs) to filter through. The higher the voltage, the more a cell “opens up.” Pros
•Direct-view models are only a few inches deep, and their pictures hold up well in bright light. •Using the same wattage lamp, a typical LCD projector will create a brighter image than a DLP model — but most DLP projectors produce enough light for just about any viewing. Cons •Of the fixed-pixel technologies, LCD has the most trouble with blacks. Some light always passes through (the cells are never completely opaque), so the best black is usually a very dark gray. Flat-panel LCDs are significantly better in this respect than they were a few years ago, however. •Because of how light goes through LCD cells, flat-panel displays usually have narrower viewing angles than plasma TVs. •Low-resolution LCDs show pixelation and screen-door effects on big screens. Front projectors with XGA (1,024 x 768) or higher resolution have a reduced screen-door effect. •Flat-panel LCDs may sometimes blur fast motion. The latest models have greatly reduced this tendency, however. Where It’s At — Prices have tumbled, with 42-inch rear-projection models available for as little as $1,500 and 42-inch flat panels for even less. LCD front projectors are priced competitively with DLP models but are less numerous. LCoS How It Works — LCoS borrows from both LCD and DLP technology. As with LCD, each pixel in an LCoS display has liquid crystals that untwist to transmit light, and — as the name indicates — these crystals are applied to a silicon chip instead of sandwiched between glass. As in DLP, light is reflected off the chip toward a screen. LCoS front projectors and RPTVs can be designed with either a single chip, using a color wheel or prisms to separate the light, or three chips, one for each primary color. Pro
•LCoS rear-projection TVs are high-resolution displays (typically 1080p) with tight pixel spacing, yielding an extremely detailed yet smooth image, especially on a very large screen. Cons •Can be expensive. •Struggles to reproduce deep blacks, though performance is getting distinctly better. Where It’s At — LCoS has had a somewhat tortured history, with most companies who have adopted it bailing out soon thereafter (apparently because the chips are very hard to manufacture in quantity). Still, the technology’s resolution capability makes it a real contender among fixed-pixel displays, especially for exceptionally large screens. JVC, which has championed LCoS for years with its high-end D-ILA front projectors, now has some RPTV models, and Sony has made a substantial commitment with its SXRD projectors. |
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Screen Size Aspect Ratio: Widescreen vs. Standard Resolution: What's HDTV and What Isn't One of the two commonly used high-def signal formats is 720p (progressive-scan), which has 720 pixel rows and 1,280 pixel columns video per frame. The other is 1080i (interlaced), which has 1,080 pixel rows and 1,920 pixel columns per frame. Both use a 16:9 widescreen frame, and if you do the math you will discover that in both formats the number of pixel columns across a width equal to the screen height is the same as the number of pixel rows. The pixels are thus said to be square. It would be nice if all HDTVs had resolutions matching one or both of the broadcast standards, but the specs can vary a lot — especially among two kinds of fixed-pixel displays, plasma and LCD. Some screens might match up perfectly with one of the high-def formats, but many have native resolutions such as 1,024 x 1,024 pixels or 768 x 1,366 pixels, so the TVs convert incoming video to match. These models are still considered HDTVs, which have come to be defined as any sets that can display at least 720 pixel rows or scan lines. Color Temperature Why does this matter? Since the largest part of a video signal consists of black-and-white information, any deviation from the white-level reference of 6,500 K — whether toward the red end of the spectrum or the blue end — will bias all images in the same way. More specifically, since the studio monitors used for color-correcting TV shows and DVD masters are calibrated to 6,500 K, your TV must be set to the same color temperature if you want it to accurately recreate the images. Contrast Ratio |
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Interlacing, Deinterlacing, and Scaling The process of converting video from interlaced to progressive scanning is known as “deinterlacing.” Although it seems straightforward enough to combine two fields of a frame and display them all at once, there are a couple of gotchas. The first is that when video is shot in interlaced format — which is how most TV and video cameras operate — the fields are shot sequentially, with the second field of a frame acquired a sixtieth of a second after the first. Any motion that occurs between the two will cause “jaggies” if the two fields are just slapped together and displayed simultaneously. Consequently, a deinterlacer must incorporate sophisticated motion-compensation techniques to achieve good results with typical video-originated material, and some are distinctly better than others in this regard. The second potential issue arises with material originally shot on film. When film is transferred to video, it is normally converted from its native frame rate of 24 fps (frames per second) to the interlaced 30 fps employed by most TV sets, using a method called 2:3 (or 3:2) pulldown to pad out the sequence with a repeated field every other frame. Video originated from film can be deinterlaced perfectly to 60-fps progressive-scan format, but only if the deinterlacer correctly detects and compensates for the 2:3 pulldown. If it doesn’t, it will create some video frames out of fields from two different film frames, causing an ugly artifact called “combing” if there is any motion between those original frames. This is why 2:3 pulldown compensation is so important in a progressive-scan DVD player. With the advent of HDTV, it has become important in TV sets as well. An HDTV set has to handle at least four basic video formats: regular old 480i standard-definition (SD) for conventional analog broadcasts and videotapes, 480p SD (mainly from progressive-scan DVD players), and the two widescreen high-definition (HD) formats, 720p and 1080i, which provide much greater picture detail. An HDTV set should, therefore, be able to accommodate inputs in a number of scan formats and in both 4:3 and 16:9 aspect ratios for standard-definition signals (4:3 is not used for high-definition broadcasts). It’s possible to design a CRT display to handle all of those formats directly, which is what high-end CRT front projectors typically do. But since it’s cheaper to convert some formats to others than to make a full-bore multiscanning monitor, most rear-projection and direct-view CRT sets take the conversion approach. And in the case of fixed-pixel displays, such as LCD, DLP, LCoS, and plasma, all incoming signals must be converted to a progressive-scan format that exactly matches the display’s pixel array. Most digital CRT sets work at 480p and 1080i and convert every other incoming signal to one of those native formats. That usually means 480i gets bumped up to 480p and, if the set has a built-in HDTV tuner, 720p gets converted to 1080i. (Because 720p actually has the highest data bandwidth and horizontal scan rate, it is easier from the display-design standpoint to convert it “up” to 1080i than to step 1080i “down.”) The process of converting between scan formats is known as scaling, and interlaced signals must be deinterlaced prior to any other processing. So deinterlacing is a critical function in all HDTV sets, especially those based on fixed-pixel displays, which in turn means that 2:3 pulldown compensation is important, since much of what is broadcast on TV was originally shot on film. Scaling is hard to do, and bad scaling can look really, really bad (especially if it starts off with mediocre deinterlacing). Historically, good scalers have been very expensive, even if all they did was line-double 480i to 480p. And the very best scalers, from companies such as Faroudja, Key Digital, and Runco, are still very pricey. The good news is that the growing need for video scaling has led to substantial progress further down the food chain — a trend that will surely continue. Still, before you buy any set with built-in scaling — a category that includes all HDTV sets and all fixed-pixel displays — cast a critical eye on how it looks with a variety of input signals. Pay special attention to what the set does with ordinary analog signals from cable or broadcast TV, which tend to give crummy scalers the biggest fits. Look particularly at what happens around the edges of moving objects. (Problems are often most apparent on slowly moving objects in the background.) Jagged or fuzzy edges or halos around objects are a bad sign. Poor handling of analog TV signals might not matter much ten years from now, but it could make you pretty unhappy in the meantime. You should also make sure the set provides 2:3 pulldown detection and compensation for film-originated programs. Understanding Our Lab Data |
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Setup Connections Getting High-Def Shows
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