How Bright Should It Be? There is no one best level for brightness, and brighter isn't always better. For a home theater projector you plan to use in a dark room, for example, 1,000 to 1,200 lumens can easily give you a large, bright image, while a 2,000-lumen projector may be so bright that it's hard on the eyes. On the other hand, for a portable data projector you expect to use in well-lit locations, 2,000 to 3,000 lumens is the right range. For large rooms, you may want something even brighter.
The point is that the best level of brightness depends on the amount of ambient light, the size of the image, and even the material in the screen you're using. If you're setting up a projector for a permanent installation, whether at home or in your office, your best bet is to buy from a knowledgeable source that can help you match brightness to the lighting conditions and screen in the room.
If you're trying to choose between two models, keep in mind too that small percentage differences in lumens—2,000 versus 2,200 for example—aren't terribly significant. Perception of brightness is non-linear, which means you need far more than twice as many lumens for a projector to appear twice as bright. Also, a projector's true brightness tends to be a little less than its rated brightness, although there are exceptions.
Don't Take Contrast Ratio Too Seriously Contrast ratio is the ratio between the brightness of the brightest and darkest areas a projector can produce. All other things being equal, a higher contrast ratio indicates more vibrant, eye-catching colors and more detail showing in dark areas on the screen. Because other factors are also involved, however, knowing the contrast ratio doesn't tell you much.
How Do You Plan To Connect? Most projectors offer at a minimum a VGA (analog) connector for a computer and a composite video connector for video equipment. If your computer has a digital output (typically an HDMI connector) you might want a digital connection on the projector as well, since it will eliminate any chance of problems like jittering pixels caused by poor signal synchronization. For video sources, the preferred connection choice is HDMI (assuming your video equipment has HDMI connectors), with component video a close second. Some projectors are now adding Mobile High-Definition Link (MHL)-enabled HDMI ports, which let you project from Android devices, and in some cases, charge them as well. Many projectors offer Wi-Fi connectivity through a (usually optional) wireless dongle that fits in a USB port that also supports projecting from a thumb drive.
What Technology Do You Want? Today's projectors are based on one of four imaging technologies: DLP, LCD, LCOS, and laser raster. (Don't confuse laser raster projectors, which actually draw the images using lasers, with projectors that simply use lasers as a light source for another imaging technology, like a DLP or LCOS chip.)
Most inexpensive DLP projectors and some LCOS-based pico projectors, including both data and video projectors, project their primary colors sequentially rather than all at once. This can lead to a rainbow effect, with light areas on screen breaking up into little rainbows for some people when they shift their gaze or something moves on screen. Those who are sensitive to this effect can find it annoying, particularly for long sessions.
LCD projectors don't have this problem, but tend to be bigger and heavier for equivalent projectors. The general consensus is that standard-size LCOS projectors offer the best-quality images, but they tend to be bigger and heavier than DLP or LCD projectors, and far more expensive. There aren't yet many laser raster projectors, so it's hard to make general statements about them. However, the one clear advantage of using a laser is that the image doesn't require focusing.