These big-screen sets are losing the bulk they were known for.

Most new rear-projection TVs are microdisplay sets that use miniature technology-liquid-crystal display (LCD), digital-light processing (DLP), or liquid crystal on silicon (LCoS)-to create large images on screens measuring up to six feet or more diagonally. These TVs are slimmer and lighter than bulky projection sets using cathode-ray tube (CRT) technology, which used to be the norm. CRT-based projection sets are now few and far between. Overall, sales of rear-projection sets have been shrinking as flat panels have become larger and low-priced.

Major brands include JVC, Mitsubishi, Panasonic, and Samsung. Sony has been a big player in this category, but it recently stopped making rear-projection sets. Hitachi, Philips, and Toshiba have also left the category. JVC and Panasonic haven't shown new models for 2008, so it's possible they're also considering an exit from the category.

The smallest sets measure about 37 inches diagonally, but most are 50 inches and larger; models with 50- to 59-inch screens are the best sellers. The largest TVs have screens measuring 73 inches or more.

Virtually all rear-projection TVs now on the market are digital HD sets. Most are 1080p models with 1920x1080 resolution, giving them the potential to display all 1,080 lines in the most common high-definition format, called 1080i. The improvement is most noticeable on screens 50 inches and up, which includes most rear-projection TVs.

CRT-based sets, which are almost gone from the market, are floor-standing models with deep cabinets mounted on casters. Some take up as much space as a love seat or sofa. Most microdisplays are less obtrusive. Most are 15 to 20 inches deep, and some "slim-line" models are now just 10 to 12 inches deep.

A stand for a microdisplay television is recommended; a matching stand, sold separately, is usually available.

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.

Rear-projection TVs have the features that are now standard on higher-priced TVs. Like virtually all new HDTVs, rear-projection sets have 16:9 wide screens. Because some TV content is still formatted for a squarish 4:3 screen, HDTV sets have stretch and zoom modes that expand or compress an image to better fill the screen. This helps to reduce the dark bands that can appear on the sides or top and bottom of images not formatted for a wide screen. (The picture might be distorted or cut off in the process.)

A film-mode feature improves the appearance of movies converted from film to video, including the majority of cinematic movies on DVD and some movies broadcast on cable, on 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. It 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 jerky and jagged around the edges. When watching DVDs on a progressive-scan player, 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 the 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 the look of standard-definition programs coming in through the component-video input.

Picture-in-picture (PIP) 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 onscreen guide while keeping an eye on the program you're watching, or keep track of a sports event while a 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 on their own.

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 high-definition 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 or video-on-demand and 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.

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-definition signals: HDMI, DVI, component-video, and RF (antenna/cable). HDMI 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. 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. 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. Inputs on the front or side of a set are more easily accessible than those in the rear, but you'll be able to see the cables plugged into those jacks.

Some projection sets have a memory-card slot. That 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. Backlit keys are preferred because glow-in-the-dark buttons often fade quickly.

On CRT-based projection TVs, auto convergence provides a one-touch adjustment to align the three CRT images to form an accurate picture. It's much more convenient than manual convergence, which can require time-consuming adjustments but allows finer control. The best bet is a set that has both manual and automatic convergence. (Convergence is not necessary on LCD, DLP, or LCoS models.) On CRT-based sets (but not LCD, LCoS, or DLP models), static images left on the screen for a long time can cause "burn-in"-ghosted images on the screen.

Consider space before settling on screen size. You might be tempted by the biggest screens, which can span as much as 73 inches or more, but take a breath-and some measurements-first. Figure out how much floor space you can actually spare, and plan to view the TV from about 7 to 9 feet away for optimal picture quality.

Consider reliability. Our surveys have shown that rear-projection TVs using CRT technology have been much more repair-prone than conventional picture-tube TVs. Microdisplays have been even more repair-prone. The overall repair rate for seven major brands of DLP and LCD sets covered in our survey was 18 percent (for sets purchased between 2004 and 2007). Toshiba and RCA DLP sets were most repair-prone. Hitachi LCD-based sets were more repair-prone than Sony and Panasonic. We don't have enough historical data on LCoS sets for a repair chart by brand, but we have enough data to see that Sony sets of this type have been more reliable than JVC sets. Despite the comparatively high repair rate, most rear-projection sets have been trouble-free in their first few years, and many of the reported repairs were covered by a standard warranty. So an extended warranty still seems like a poor investment for most consumers.

Focus on picture quality. The best rear-projection sets can deliver excellent picture quality with HD content, DVDs, and regular TV programs. Within the microdisplay category, we haven't found that any one projection technology was consistently better than another. There are a growing number of sets that offer 1080p resolution, and some of those have been among our top-rated performers.

Check the viewing angle. Some new models do a better job than older sets at maintaining their image quality when viewed from off-center-a must if the TV will be watched by several people at once. Before buying one, see how the picture looks if you step off to the side or move up and down. With some, you'll see a dimmer, somewhat washed-out image as your viewing position angles away, particularly in a vertical direction.

Consider logistics. Rear-projection sets stand on the floor or rest on a stand, so installation is easier than for front-projection systems or wall-mounted plasma TVs. Still, rear-projection sets are large and can be difficult to transport and set up so consider having the set delivered.

Consider bulb life. Most rear-projection microdisplays use a backlight with a claimed life expectancy of about 5,000 hours. You'll hit that point in about four years if the TV is turned on for four hours a day. When a bulb burns out, you won't see any picture; most sets have an alert of some type to indicate you're nearing the end of the rated life, so you won't be caught by surprise. Replacement bulbs cost from $200 to $400.

Replacement isn't that difficult-no harder than replacing a car's headlight-so you can do it yourself as long as you're comfortable wielding a screwdriver. You can also pay for professional installation, which can add another $200 or so to the cost of replacement.

A few new models have longer-life bulbs; one we've seen was rated at five years. Others, such as Samsung, are using LED illumination instead, and one company, Mitsubishi, is expected to introduce later this year a model lit by lasers. These types of backlights can expand the range of colors the set can display and eliminate the need to replace the bulb during the life of the set.