These display devices can provide the biggest picture, but they aren’t ideal for everyday use.

For a truly theater-like experience, you can't beat a front projector paired with a screen that stretches 100 inches or more diagonally-about twice the size of most plasma and LCD HDTVs. You can get excellent high-definition picture quality in a jumbo size for about the same price you'd pay for a big-screen flat panel.

With a front projector, you're not locked into a specific screen size as you are with every other type of TV. Front projectors require a separate screen or a smooth wall as a display surface. You can vary the picture size from about 50 inches to about 200 inches by moving the projector closer to the screen or farther back, and using the zoom control.

Technically display devices rather than TVs, projectors require additional gear to provide you with entertainment. To get TV programming, you must connect an external tuner, such as a cable or satellite box. For movies, you can hook up a standard or high-def DVD player. You generally have to provide an amplifier or A/V receiver and speakers, because most projectors don't have built-in audio capability. When speakers are included, they're generally not of the highest quality, so you'd probably want to use a sound system anyway.

Despite their advantages, front projectors aren't the best choice for typical, everyday viewing. The picture from a projector looks best in a dark room, because any light that falls on the screen reduces contrast and washes out the picture. Your best bet is a room with blackout window shades. Even at night, you have to keep light from nearby lamps from hitting the display surface.

Also, the need to add a screen, speakers, and a TV tuner increases the cost and complexity of set-up. In addition, a projector's bulb typically needs replacement every 2,000 to 3,000 hours or so.

In years past, the only real choice for a big-screen home theater was a bulky CRT-based projector that cost tens of thousands of dollars. Most new projectors are compact units using LCD, DLP, or LCoS technology-the same display technologies used in rear-projection microdisplay HDTVs. Among the best-selling brands of home-theater projectors are Epson, JVC, InFocus, Mitsubishi, Optoma, Panasonic, Sanyo, Sharp, and Sony.

Prices for front projectors have dropped considerably during the past 12 months. There are now 720p HD models that cost about $1,000. Models with 1080p resolution are more expensive ($2,500 to $6,500 or more), but that's only half the price they were just a year ago.

Several companies, including Epson and Optoma, offer all-in-one home-theater projector packages with either an integrated or outboard DVD player and built-in speakers, plus a screen. These are designed to be used with standard DVDs, so they don't offer HD resolution. They cost less than typical front projectors and are somewhat easier to set up and use. There are also now all-in-one systems with 720p resolution that can display high-def content.

Don't confuse home projectors with the cheaper "presentation" models designed for conference-room use. Those units, which sell for less than $1,000, might have lower resolution, which won't give you a detailed, big-screen TV image. Data projectors also tend to lack typical TV features, such as aspect-ratio controls (including zoom or stretch) and color controls.

Maximum image size. Manufacturer specs indicate the largest image you can get from a given model.

To achieve the maximum size, you have to move the projector farther back from the screen. But as the image gets larger, it also gets dimmer. In our tests, we found an image size of about 110 inches (measured diagonally, for a 16:9 widescreen display) to be the sweet spot for impact and brightness.

Distance to screen. To fill a 110-inch screen, you'd typically place a projector 10 to 15 feet away. For a 50-inch image, about half that distance would do. Recommended placement varies by model; see what the specs indicate.

Keystoning. If you tilt the projector up or down to raise or lower the projected image, the sides of the image will start to angle away from 90 degrees. That turns what should be a rectangular shape into a trapezoid. A keystoning control feature compensates for this, but resolution can suffer depending on the amount of correction applied to the image.

Lens-shift mechanism. This feature lets you move the image horizontally or vertically without tilting the projector, so you can get a straight, geometrically correct picture even if the projector can't be centered directly in front of the screen without the shortcomings of the keystone adjustments. The electronic shift adjustment on some projectors tends to have a very limited range. When exceeded, images could be cropped.

Dynamic/manual iris. A manual or dynamic iris acts as a brightness adjustment by varying (typically reducing) the amount of light sent to the lens, effectively boosting contrast. While a manual iris lets you reduce overall light output to improve black-level performance, it applies that light reduction across the entire picture, so whites won't be quite as white. A dynamic iris, which is controlled by a motor, has circuitry that automatically closes the iris during darker scenes and opens it up again for brighter scenes. It must be able to react accurately and quickly or the process will be noticeable, an effect known as "breathing."

Stretch and zoom modes. These aspect-ratio controls will adjust the image size to fill the screen shape better. This helps reduce or eliminate the dark bands that can appear above, below, or on the sides of the image. (The picture may be distorted or cut off a bit in the process of stretching and zooming.)

Inputs. Most projectors have at least one HDMI and one component-video input to handle HD signals. Most also have S-video and composite-video inputs, and many have a computer input.

First make sure that a front projector is the right choice for your viewing needs. If you can deal with the logistics, you can enjoy a high-quality, theater-like experience at a reasonable cost. Here's what to consider in choosing among models:

Go for HD. If you're going to the effort of setting up a front-projection system, we highly recommend an HD model-a 1080p unit if budget permits. Rapidly falling prices have made them much more affordable, and the higher quality will be clearly visible on the larger screens. A low-cost everything-is-included model would be suitable for casual movie viewing.

Weigh the pros and cons of LCD, LCoS, and DLP projectors. In general, projectors using LCD technology haven't been as good as DLP models at reproducing true black, but recent improvements have enabled some LCD projectors to do quite well. LCoS projectors, from companies such as Sony and JVC, are becoming more common as prices fall, and some are outstanding.

When watching a DLP front projector (or rear-projection set as well), you may experience a "rainbow effect." This is a flash of color some viewers notice mainly when they move their eyes across bright objects on a dark background. The rainbow effect isn't obvious, but once noticed, it can be annoying. Many newer DLP projectors now use faster-spinning color wheels, which can reduce the effect. Take a video with high-contrast scenes to the store so that you can see whether it's a problem. All DLP projectors using a single chip (including all models in the Ratings online) are affected. Only the priciest DLP units avoid the problem by using three chips to produce red, green, and blue and eliminating the spinning color wheel.

Decide on a room arrangement. Before buying a front projector and screen, figure out how you'll set up the room. Front projectors can be placed on a table or other flat surface and stored when not in use. Most can also be mounted to the ceiling. If you mount the projector, be sure to place it at the distance recommended by the manufacturer, angled to prevent the rectangular shape of the image from being distorted. Projectors with a vertical and/or horizontal lens will give you more placement flexibility; those without a lens shift have to be mounted or placed so their image is centered on the screen to avoid using the keystone adjustment, which can distort the picture.

The room dimensions and anticipated seating positions will largely determine what screen sizes are practical. Some projectors give you more flexibility in where you can place the projector to get a certain image size; see what the manufacturer recommends. Models with "short-throw" lenses can be placed closer to the projector, while "long-throw" lenses allow the projector to be placed farther away.

The larger the image you want, the more distance needed between the projector and screen, though the projector's zoom feature will provide some flexibility here. Keep in mind that as the image from a projector gets larger, it also gets dimmer, with poorer contrast between light and dark areas. Also consider where you'll sit to watch the TV. With a 110-inch screen and an HD image, the optimal viewing distance is about 14 feet.

Evaluate logistics. Think about where you'll place the cable or satellite box that will serve as the TV tuner, a sound system, and probably a DVD player or recorder. Most projectors have at least one HDMI input and one component-video input, but you may need more if you won't be using a receiver to switch between signal sources. If you want to use the projector for playing games, make sure it has a computer input. Front projectors can be placed on a table or other flat surface and stored when not in use. Most can also be mounted to the ceiling. If you mount the projector, be sure to place it at the distance recommended by the manufacturer, angled to prevent the rectangular shape of the image from being. Hiding cables and wiring behind walls or above the ceiling may require construction work, and you must use cables specifically rated for in-wall use.

Think about the screen. In our tests, we used a 110-inch screen that cost $400. It has a matte-white viewing surface 41⁄2 feet high by 8 feet wide. There are screens with more reflective finishes (called gain) designed to enhance brightness, but they might have a narrower viewing angle than a matte screen. Other so-called dark screens are designed to enhance contrast by improving black-level performance, but they do take a small hit in overall brightness. Freestanding screens can be folded and stored when not in use, and some wall- or ceiling-mounted screen can be manually or electronically retracted.