More and bigger screens are adding variety to the category.

Plasma TVs make a blockbuster first impression. A scant 6 inches thick or less, these sleek, flat panels display bright images on screens measuring 42 to 60 inches or more diagonally. Given those large sizes, plasma TVs have become a viable alternative to rear-projection sets for anyone seeking a jumbo screen.

A plasma screen has as many as two million pixels containing gas that’s converted into “plasma” (ionized gas) by an electrical charge. The plasma emits ultraviolet light that causes phosphors to glow red, green, or blue, as dictated by a video signal.

Because of improvements in plasma technology, the best sets have excellent picture quality, in some cases, the best we’ve seen. They also offer a wider viewing angle than most LCD TVs and rear-projection sets, with deeper blacks and smoother motion than you typically get with LCD sets.

But the shiny screen of a plasma TV can produce annoying reflections, especially in bright rooms. Many plasma sets have screen coatings to reduce reflections. Like projection TVs using CRT technology, plasma sets are vulnerable to screen burn-in, although new screen-saving technologies minimize the risk.

Plasma TVs with 1080p resolutions are becoming more numerous, especially in sizes 50 inches and up. Manufacturers are working on new sets that are even thinner and lighter, with lower power consumption, than the plasma TVs now on the market. These could arrive on the market soon.

There’s growing evidence that plasma TVs are highly reliable products requiring few repairs during the first three years of use.

Among the leading brands in the plasma TV category are Panasonic, Hitachi, LG, Pioneer, and Samsung. Sony was a leading manufacturer but has stopped making plasma TVs to concentrate on LCD sets. Prices have dropped sharply over the past year. HD models with 42-inch screens start at around $1,000. TVs with screens 50 inches or larger start at less than $1,500. The lowest-priced sets are often from emerging brands, such as Maxent and Vizio.

Look for prices to fall further as the technology matures and plasma faces increasing price pressure from LCD HDTVs.

Most 42-inch plasma HDTVs have a resolution of 1024x768; 50-inch sets have typically had 1366x768 resolutions, but more new plasma TVs have a still higher resolution of 1920x1080. These so-called 1080p TVs have the potential to display all 1,080 lines in the most common high-def format, 1080i. The improvement is most noticeable on large screens, say those 50 inches and up.

Since March 2007, all new TVs sold in the U.S. must include a digital tuner. This enables them to receive free digital TV, including high-def programming, via an over-the-air antenna. However, some sets are sold as “monitors,” meaning they have no built-in tuner of any type. These require a cable box or satellite receiver, or set-top box and antenna, to receive any programming, not just HD content.

Plasma TVs have all the usual features you expect on a higher-priced television. Like most new HDTVs, they have 16:9 wide screens. Because some TV content is formatted for the more squarish 4:3 screen, HDTV sets have stretch and zoom modes that expand or compress an image to fill the screen better. This helps to reduce the dark bands that can appear on the sides or top and bottom of images if you watch content that isn’t formatted for a wide screen. (The picture might be distorted or cut off in the process of stretching or zooming.) A film-mode feature improves the appearance of movies converted from film to video, including most cinematic movies on DVD and some movies broadcast on cable, satellite, or over the air. This feature is also called 3:2 pull-down, motion compensation, or brand-specific names such as CineMotion and Film Mode.

This helps compensate for the difference in frame rates between film (24 frames per second) and video (30 frames per second), so moving images look less jagged around the edges. Progressive-scan DVD players have this feature as well. When watching DVDs, try enabling that feature first on the DVD player and then on the TV, and use whichever makes the images look smoother.

All TVs have menus with settings that enable you to adjust the video, audio, and more. With more sources for video available all the time, it’s handy to have a feature that allows you to customize settings for each input, such as the one you routinely use for your cable box or DVD player. For example, you might want sharpness set to its lowest level when watching high-quality DVDs routed through the HDMI input, but a higher sharpness setting to improve standard-definition programs coming in through the component-video input.

CableCard slots on a small number of HDTVs let you use a card, provided by the cable company for a small rental fee, instead of a cable box. When the card is inserted, the TV can receive scrambled digital cable content, including HD programming. This eliminates the need for an extra piece of equipment and cables, but there is a downside. Current CableCards are one-way, so they don’t provide an interactive program guide, video-on-demand, or pay-per-view ordering. But some TVs have a built-in program guide, such as TV Guide On Screen, that displays eight days of programming in a searchable, interactive format.

Picture-in-picture lets you watch two channels at once, one in a small box, the other a full-screen image. It’s useful if you want to browse the on-screen guide while you’re watching a program, or keep track of a sports event while another program is playing.

A single-tuner TV requires another device with a tuner, such as a VCR or cable box, to display two programs at once; dual-tuner models can display two programs simultaneously.

One of the most important points to consider with any TV is the number and type of inputs it has. There are several types that can handle high-def signals: HDMI, DVI, component-video, and RF (antenna/cable).

HDMI and DVI inputs provide a digital connection to devices such as DVD players, digital-cable boxes, and satellite receivers. HDMI carries audio and video on one cable. DVI carries only video and must be used with separate audio cables; they are much less common than HDMI. The digital-to-digital connection might enhance picture quality, though that hasn’t always been the case in the tests we’ve conducted so far.

Component-video inputs are analog; they use red, green, and blue RCA jacks to carry the video and must be used with separate audio cables. Most new TVs have two component-video and two HDMI inputs; some have three or four HDMI inputs. The RF input can be used to get digital signals, including HD, from an off-air antenna.

Other analog inputs on new TVs include composite-video and S-video, which are used mostly for equipment such as VCRs and DVD players. Inputs on the front or side of a set are more easily accessible than those in the rear, but are also more visible.

Some plasma sets have a memory-card slot. This enables you to view still photos or videos from a digital camera. You can connect a camera or camcorder directly to the TV if it has a PictBridge, USB, or IEEE 1394/Firewire input. A VGA input lets a TV accept signals from virtually any computer; DVI inputs are compatible mostly with newer midrange computers.

A headphone jack is handy if you want to listen to TV without disturbing others. An illuminated remote is handy in a dim setting. Backlighted keys are preferred because glow-in-the-dark buttons often fade quickly.

Plasmas also have features more specific to this type of TV. Many have screensaver-type features to prevent burn-in from static images. On some models, the speakers are on both sides of the screen; on others, they’re below the screen. Some can be detached and placed elsewhere. That affects the width of the set and could determine whether it will fit into an entertainment center. A few models have no speakers; they have to be used with an audio system to get sound.

Decide on screen size. The size of your room and your budget are key factors in choosing a screen size. Generally, a 42-inch plasma set is a reasonable choice for a main TV that you’ll watch often in a midsized room. For a large room or a home theater, consider a 50-inch-or-larger TV.

With any set, make sure you sit at the appropriate distance. Run-of-the-mill non-HD programming tends to look better and more natural if you sit at least 5 feet from a 42-inch set and 6 feet from a 50-inch-or-larger TV. If you’re closer, you’re likely to see the screen elements making up the picture along with any flaws in the images, such as graininess or video noise. With a good TV displaying top HD content, say, from a high-definition DVD player, the finer detail and superior quality allow you to sit closer so you can more fully enjoy the impact of a larger image.

While those screen sizes might sound enormous, keep in mind that big-screen plasma sets are just a few inches deep, so they aren’t as imposing as you might fear. Be sensible, though. Measure so you don’t overdo it.

Consider a 1080p TV first, but don’t rule out 720p sets. Another major decision point involves a TV’s native screen resolution, which indicates the number of pixels, or picture elements, on the screen. The more pixels, the finer the detail a screen can display. You can appreciate that level of detail most on a 50-inch-or-larger TV, but you might see subtle improvements on a 42-inch screen, especially when viewed up close.

No TV programs are broadcast in the 1080p signal format now, but a 1920x1080 set will convert current HD signal formats (720p and 1080i) to match its native screen resolution. If the TV does the job well, the picture quality can be outstanding. In addition, Blu-ray and HD DVD players provide true 1080p content from HD movies.

If price is not an issue, we’d recommend a high-scoring 1080p set over a comparable 720p set. But don’t assume all 1080p sets are superior to 720p models; resolution alone doesn’t determine picture quality. Some of the top-rated TVs in our Ratings are 720p sets. Also, with typical HD programming, picture quality of a good 720p set can be almost indistinguishable from a 1080p set’s, especially if it’s smaller than 50 inches.

Beware of burn-in, but don’t worry about burnout. Plasma TVs might be prone to burn-in, much like CRT-based rear-projection TVs. Over time, static images displayed for long periods (such as a video game or a stock ticker) might leave permanent, ghosted impressions onscreen, so minimize the risk as much as you can. Most new TVs have screen-saver features to minimize the risk, but don’t leave static images onscreen for prolonged periods. We’ve seen no burn-in during our short-term tests, and anecdotal evidence from our staffers and online forum participants hasn’t indicated any issues during typical long-term use at home.

You may have seen reports suggesting that plasma TVs might not last as long as other TV types. Ignore these claims, as there is no evidence to that effect. A plasma TV should last a good 10 years or so in normal use.

Consider reliability. Our most recent survey found few repair problems during the first three years of use for plasma sets from Panasonic, Pioneer, and Samsung. Philips plasma sets needed more repairs than average. Hitachi plasmas look promising but we don’t have enough data to include this brand in our charts.

Our survey of thousands of consumers showed that plasma flat-panel TVs have been reliable for the three-year period covered by many extended warranties, so there’s little sense in spending several hundred dollars for such a warranty. You can also get longer coverage without paying a cent for it. Some credit cards add up to a year to your warranty at no cost when you buy a TV with their card. Some retailers do, too. Costco, for instance, offers a two-year warranty for sets bought in its warehouses or on its Web site.

Don’t get hung up on specs. Ads touting high contrast ratios and brightness (in cd/m2, or candelas per square meter) might sway you to one set over another. But don’t let this be the deciding factor. Manufacturers arrive at specs differently, so they might not be comparable. Try adjusting sets in the store to compare contrast and brightness, as TV displays are often optimized for bright retail environments, not home viewing.

Determine what’s included when comparing prices. A few plasmas are monitors only; they don’t include speakers or a tuner for an over-the-air TV signal. You won’t have to buy a tuner if you’ll be using a cable box or satellite receiver, which will serve as the tuner for all programming. Otherwise, you’ll need a set-top box to work with an antenna. If the plasma TV has no speakers, you’ll have to buy them separately unless you plan to connect the set to your existing sound system.

Think about the logistics. You might want to consider having your plasma TV delivered, especially if it’s one of the larger sets. The cartons can be heavy and awkward to carry. You might be able to handle a basic hookup of a cable box or satellite receiver and a DVD player on your own. If you’ll be connecting more devices, a DVR, DVD recorder, VCR, and digital receiver and sound system, it gets trickier, so you might want to consider professional installation at some point.

Though ads for plasma TVs often show no cables or wires, they are a factor in installation. You can tuck wires behind the TV if you place it on a stand. With wall mounting, you can run the wires behind the wall or through conduits, a task that might be best handled by a professional (wires that run in walls and ceilings require a different UL rating).

Many plasma TVs weigh 100 pounds or more, so they need adequate support. They also require good ventilation because of the heat they generate. Ask the retailer to recommend an installer or contact the Custom Electronic Design & Installation Association (800-669-5329 or www.cedia.net) to find one in your area.