A review of "digital light processing" projectors in the May 30 Business section, which found that the table-top displays offered picture quality as good as conventional high-definition television sets, should have explained that their use of image-processing and scaling techniques means they do not meet the commonly accepted standard for high-definition television. That standard holds that an HDTV set must display a high-definition picture at a certain minimum resolution without using such techniques. (Published 6/12/04)

In the pricey world of high-definition TVs, digital projectors -- once reserved for business presentations and high-end home theaters -- now offer an unlikely combination of virtues: enormous, flat screens at relatively cheap prices of around $1,000 each.

These tabletop digital light processing (DLP) projectors work like film projectors, throwing a moving image onto a wall or screen at sizes from 20 to 200 inches, as measured from corner to corner. (DLP technology is also used in pricier rear-projection HDTVs; in those sets, the image is projected toward the viewer and onto a regular glass screen.)

Since they don't include their own screens, they're cheaper than all but the smallest HD sets and hardly more expensive than standard-definition projectors.

We tested three recent models: BenQ's PB6100 ($999), Hewlett-Packard's vp6111 ($1,300 before a $300 rebate) and InFocus's X2 ($999). In some respects, these devices (between 51/2 and 61/2 pounds each) work alike: They all accept regular analog TV and computer input in addition to high-definition digital signals -- which, however, can only be pulled in with a separate cable, satellite or over-the-air receiver.

Before you can sit down and watch high-def programming splashed across your wall, they all require a similar setup process. Their remote controls allow easy control of such settings as brightness, contrast, color and digital "keystone" (if the projector sits at an angle, this squares the corners of the image so it looks normal).

The one-time job of focusing, unfortunately, must be done with a manual knob, which can be a nuisance if you've placed the projector far away from the seats to escape one unpleasant aspect of this technology: noisy fans used to cool the hot lamp inside each projector. The HP was the worst offender in this respect; its fan generated an irritating, inconsistently wavering whine that was hard to ignore.

We tested these three models against bare white walls, light green walls and a Vutec SilverStar screen, sold in various sizes for prices ranging from about $1,000 to $2,500.

In darkened rooms, the ideal setting for watching any kind of projected images, all three projectors did well, delivering crisp, bright and clear images. HDTV looked especially vibrant, but even such computer images as Web pages and word-processing documents were readable. The surprise was how well these projectors worked with some ambient light in the room. The InFocus X2 did best overall in both dark and moderately lighted settings. (Direct sunlight, however, will wash out the image in most cases.)

Also surprising: Projecting TV images against the green wall instead of the white one didn't degrade the colors of the picture. The only real trade-off was a slight drop in brightness.

These DLP projectors did, however, sometimes struggle to reproduce darker shades properly. Black sometimes looked more like dark gray, and in gray areas details could disappear. The Vutec screen, a light gray sheet mounted on the wall, helped a lot in these cases, lending better contrast and richer colors to images projected on it.

For everyday TV viewing, we'd go with any of these models, with the InFocus as an overall favorite. The others didn't quite match up to its picture quality in moderately illuminated settings. They do, however, offer some features of their own. The BenQ, for example, allows for picture-in-picture display if fed two different video signals, while the HP allows easy switching between TV and computer inputs.

All of these projectors do come with one form of required maintenance that will be unfamiliar to most TV owners: The light bulbs that project their images must be replaced every 2,000 hours or so of use, and new ones cost hundreds of dollars.

Still, it would take several bulb replacements before you came close to the price of a big-screen plasma or LCD HDTV -- something to consider if you've got the wall, and the window shades, to allow projection HDTV.

Digital projectors offer HDTV for less: from left, the Hewlett-Packard vp6111, InFocus X2 and BenQ PB6100.