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The Honolulu Advertiser
Posted on: Tuesday, January 31, 2006

Light shed on digital projectors

By Kim Komando

Like to watch television? Home digital projectors let you experience movies, sitcoms and sporting events in blockbuster-sized proportion. Before rushing out to the store, here are three things to know about digital projectors.

1. Types of projectors. Like televisions, projectors use different technologies to display images. For the most part, you'll find LCD (liquid crystal display) and DLP (digital light processing) models. You may encounter CRT (cathode ray tube) models, but these are bigger and much more expensive (about $10,000).

LCD projectors work by passing light through LCD glass panels one each for the red, green and blue components of the video signal. As light passes through these panels, tiny pixels short for picture elements switch on and off to create the image. That image is then projected through a lens to a large screen. These projectors are capable of producing high-definition TV-quality images. The downside to LCD projectors is that the pixels can be seen in a large viewing area, producing what's known as a "screen door effect."

DLP projectors work differently than LCD projectors. The DLP chip uses tiny mirrors each representing a pixel that react to light from the projector's lamp to create high-quality images that are sent through the lens to the screen. High-end DLP projectors use three chips, one for each of the three primary colors, but most sets use only one chip. Lower-end sets with one chip use a color wheel with red, green, blue and sometimes other color filters to create images. The only downside is that this can sometimes exhibit a rainbow effect. But this occurs infrequently and only if a viewer quickly looks from side to side on the screen.

2. Brightness and contrast ratio. The brightness of the projected image is measured in lumens. Home theater projectors usually have brightness ranges of 700 to 2,000 lumens. A projector with 800 lumens should be sufficient in most viewing conditions. But if you are watching movies in a brightly lit room or one with a lot of ambient light, you'll need more lumens.

Also, look for projectors with good contrast ratios. The contrast ratio helps produce crisper images by clearly separating white and black. Low contrast ratios can produce washed out images. You'll want a projector capable of at least a 1,500-1 contrast ratio.

3. DVD player/projector. The Optoma MovieTime DV10 (www.optomausa.com; $1,500), Cinego D-1000 Instant Theater (www.radioshack.com; $1,300) and Hewlett-Packard ep9010 Instant Cinema Digital Projector (www.hp.com; $2,000) have built-in DVD players. The advantage is that you can watch a movie wherever you want, without regard to where your DVD player is located.

Although digital projectors produce clear images comparable to that of a big-screen TV, don't throw out your television set just yet. Use it for day-to-day viewing and bring out the projector for movies and sporting events.

Why? The light bulbs that projectors use are fairly expensive. Expect to pay $200 to $500 to replace them. And the bulbs don't last very long, generally 1,000 to 4,000 hours. This sounds like a lot, but the average American spends almost 1,500 hours a year watching TV. At that rate, you'll be replacing a bulb every other year.

Contact Kim Komando at gnstech@gns.gannett.com.