What Kind of Images Do You Plan to Show?
There are four basic kinds of images you can show on a projector: data, video, photos, and games. Any projector can show any kind of image, but it's important to understand that any given projector can handle one kind of image well without necessarily doing a good job on other kinds. Naturally, you'll want a projector that does a good job with the kind of images you plan to show.

Most models are sold either as data or business projectors, or as home theater, home entertainment, or video projectors. In addition, a small, but growing number are sold as models for game play .

Data projectors will most likely do well with data images, like PowerPoint presentations, spreadsheets, and PDF files, while home theater projectors are best at handling full-motion video well. Any projector that handles video well should also do a good job with photos, since photos have a lot in common with video, but without the added complication of movement, which opens the door to additional image artifacts.

Games require some of the capabilities you need for data images and some that you need for video images. If you want to use a projector for projecting your video games, and can't find a review or see a demo that specifically relates to image quality for games, look for a model that handles both video and data images well.

How Portable Does the Projector Need to Be?
Consider how portable the projector needs to be. You can find models with sizes and weights ranging from small and light enough to fit in a shirt pocket to large and massive enough to be suitable only for permanent installation. If you want a data projector to carry to business meetings for presentations, a model to take to a friend's house for serious LAN party, or a home-theater projector you can stow away when you're not using it, then be sure to pick an appropriate size and weight. The more you plan to carry or move it around, the smaller and lighter you'll want the projector to be.

What Resolution Do You Need?
Ideally, you should match the projector's native resolution (the number of physical pixels in the projector's display) to the resolution you expect to use most often, whether you're planning on connecting to a computer, video equipment, game box, or some combination of the three. Projectors can scale images up or down to their native resolutions, but they lose image quality in the process.

If you plan to show data images, you should also consider how detailed the images will be. For a typical PowerPoint presentation, SVGA (800 by 600) is easily good enough, and getting an SVGA projector will save money compared with getting one with a higher resolution. The more detailed the images, however, the higher resolution you'll want.

For video, 1080p resolution is the best choice, assuming you have a Blu-ray player, upscaling DVD player, or other 1080p device. If there's any chance you'll be watching video at lower resolutions, check out how well the projector handles those resolutions too. We are starting to see 4K projectors, with horizontal resolutions on the order of 4,000 pixels, but they're still very expensive, and as yet little content is available that can take advantage of their ultra-high resolution.

Do You Need a Widescreen Format?
For video and games, you'll almost certainly want a widescreen format. For data projectors, native widescreen resolutions such as WXGA and even 1080p, have become common. If you create your presentations on a widescreen notebook or monitor, they may look better if you project them in the same format as well.

How Bright Should the Projector Be?
There is no single 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, while2,000 lumens 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 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 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 that small percentage difference in lumens—2,000 versus 2,200 for example—isn't terribly significant. Perception of brightness is nonlinear, 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.

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, you may also want a digital connection on the projector, because it will eliminate any chance of problems, such as 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 models 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 models that simply use lasers as a light source for another imaging technology, like a DLP or LCOS chip.) Most inexpensive DLP projector and some LCOS-based pico projectors, including both data and video models, 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. 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.

Do You Need Audio?
Not all projectors have audio capability, and for those that do, the audio is sometimes all but useless—particularly with highly portable projectors. If you need sound for your presentations or for watching video, make sure that the built-in audio, if any, is both of high enough quality and loud enough to meet your needs. Alternatively, consider using a separate sound system, like powered external speakers.

Do You Need 3D Support?
Showing images in 3D for educational, business, home video, and game applications is one of the leading-edge features for projectors today, and more and more projectors are claiming to be 3D-capable.

Several 3D schemes are available, which means that just because a projector is 3D-ready doesn't necessarily mean it will work with the 3D source you want to use. For example, a given projector may work with TI's DLP-Link, which requires a computer with a quad-buffered, Open GL, 3D-compatible graphics card, but not work with a 3D Blu-ray player. The good news is that a growing number of 3D-capable projectors can project 3D content from a Blu-ray player, TV set-top box, or similar image source. If you want a projector for 3D, make sure it will work with the specific 3D image source you plan to use it with.

Do You Need a Big Image in a Small Room?
Finally, consider whether you need a short throw—meaning the ability to cast a given-size image at a short distance from the screen. Short-throw projectors let you throw a large image in tight spaces, and also minimize the risk of people getting in front of the projector and blocking part of the image.

There are no universally accepted definitions for what counts as a short throw, but as an example, while most projectors can throw an approximately 6-foot-wide image from roughly 12 to 15 feet away, most short-throw projectors need 3 to 6 feet, and ultra-short-throw projectors generally need less than a foot.

Downsides of short-throw, and especially ultra-short-throw, projectors are that they are more expensive than traditional models with long-throw lenses, and tend not to do as well in large conference rooms and small auditoriums.

At PC Labs, we review around 100 projectors every year, evaluating their features and putting them through rigorous performance testing. The models highlighted below span a wide range in purpose, features, portability, and brightness and our overall top picks. For more specific needs, check out our favorite portable projectors and models for home use.