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Contrast Ratio. This is the figure showing how the blackest blacks compare with the whitest whites'the higher the contrast ratio, the clearer the image. A high ratio is particularly critical when the projector is used in a room with the lights on. If the ratio is too low, the image will appear washed out. DLP projectors tend to run in the range of a 2,000:1 contrast ratio.

Brightness, measured in lumens. A rating of 1,000 lumens is adequate for small conference rooms where you can shut out other light sources. Larger rooms or areas you can't black out, such as lobbies or convention halls, require higher ratings.

Resolution. Common resolutions include SVGA (800 by 600 pixels), XGA (1,024 by 768), SXGA (1,280 by 1,024) and UXGA (1,600 by 1,200). Projector specifications will list a 'native' resolution, which shows the actual output. Compression technology permits display of data accepted in other formats. For optimum picture quality, it is best to match the projector's native resolution with the resolution of the data source, such as the notebook PC providing the graphics.

Weight. The lightest devices weigh about 2 pounds, which makes them ideal for travel. For office units that might be moved from one conference room to another, models in the 5- to 10-pound range are good. For permanent installations, weight is not a consideration.

Cost. DLP units have gone below $1,000, and prices will continue to drop, though the least expensive models will not necessarily meet your needs.

Bulb life. Most bulbs last between 1,000 and 2,000 hours, plenty for occasional use, but only six to 12 weeks if the projector is in constant use. Some units have an economy mode that cuts down the brightness and extends the lamp life.

Zoom. Image size can be adjusted by using a zoom lens with digital zoom.

Keystone correction. Keystoning is the term used to describe the distortion of an image that results when the projector is at an angle to the screen, rather than directly centered on it. Most projectors have electronic circuits to compensate for this distortion. But this feature does result in lower resolution in parts of the image, so it's best to place the projector directly in front of the screen.

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