The second key specification for video projectors is resolution. As for computer screens, this resolution is expressed using the number of horizontal and vertical pixels that make the image, as in 1280 by 720. Thus, when shopping for a video projector for use with a computer, you can use resolution as a guide the same way you would for any other computer display.
When you're adding a video projector to a home theater, you'll need to choose the resolution with greater care. Broadcast TV and streaming video identify their resolutions using only the horizontal number of pixels followed by a letter indicating how the screen draws each frame, as in 720p and 1080i. For recorded content, note that DVDs have a resolution of 720p and Blu-ray discs have a resolution of 1080p.
Once you know the resolutions in your video content, consider how that impacts your video projector selection. For the best quality projection results, you'll want to ensure that the projector's horizontal number is at least as high as that of the videos you want to view. For example, a projector that's Wide XGA (WXGA, 1280 by 768) is excellent for videos streaming in 720p, and a projector that's high definition (HD, 1920 by 1080) is great for Blu-ray discs and 1080i HDTV [source: Projector People].
While this is the ideal situation, you still have the option to view higher resolution video on lower resolution projectors. If you do so, expect that the picture quality is only as good as the projector. You can also view lower resolution content on higher resolution projectors. In this case, expect the image projected to be smaller or to have lower quality when it stretches to fit the larger resolution screen.
Next, let's look at the other key specifications, brightness and contrast, and how their values may not always be what they seem.