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One group of projectors consists of traditional portable models that use replaceable, high-intensity lamps with brightness levels rated in the thousands of lumens and powerful enough to display presentations in large, well-lit conference rooms. These high-performance models typically provide lots of features, including multiple connectivity options, high native resolutions--such as 1280 by 800 widescreen--and optical-zoom lenses capable of increasing the display size at greater projection distances.

The other projector type is a new breed of lamp-free, miniature models that use LED (light emitting diode) illumination with brightness levels rated in the hundreds of lumens. Though these LED units are smaller than traditional models, they're bigger (and brighter) than pocket-size pico projectors , which weigh just ounces and are capable of projecting small, low-resolution images from portable media players, netbooks, and other mobile devices.

Unlike pocket pico projectors , which work best in darkened rooms for limited viewing by a couple of people, LED ultraportables are useful as laptop companions for small-group presentations, and as portable entertainment devices for photos, videos, games, and DVDs. Still, these models aren't as full featured as traditional portables: Generally they offer fewer connectivity options, lower native resolution, and smaller (fixed focal length) lenses, but they are fully capable of displaying presentations in small rooms with low lighting.

Source: Washington Post