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Standard and Widescreen Formats Explained

A Projector Panels' 4:3 Format Ratio

As you can see, (almost) all of the projector fixed resolutions are in a 4:3 ratio format (horizontal:vertical). That is, the projector's internal panel, onto which the incoming image must be mapped, is a bit wider (by 1.33 times) than it is high. This is the industry standard for most portable home-theater projectors.

Projecting a Standard TV Broadcast

This 4:3 ratio/shape is exactly the same as a standard TV signal (NTSC) and picture tube. An incoming standard TV video signal consists of 480 lines of usable video resolution (the actual broadcast signal contains 525 lines of video information, but only approximately 480 lines are used as visible information). When displaying a standard TV broadcast with an LCD or DLP projector, the incoming image will first be expanded so that it corresponds/maps to the resolution of the projector's internal panel (either exactly 800 pixels wide x 600 pixels/lines in height if SVGA, or 1024 x 768 if XGA). And, as previously mentioned, a mathematical algorithm is used to add/interpolate pixels within the expanded image, so that the density of pixels will remain the same as the original signal. The resulting image, when projected, will completely fill the 4:3 ratio screen top-to-bottom and left-to-right, regardless of its size, with a bright, dynamic picture.

True "Home Theater" and its 16:9 Format Ratio

True "Home Theater" signals mimic the shape of a movie theater screen rather than a standard TV. That is, the ratio of width to height is much more exaggerated, in a ratio of 16:9 (1.78 times wider than high) rather than 4:3 (1.33).

For example, high-definition television (HDTV) comes in two different formats, both of which are in a 16:9 ratio: 720p (720 lines of resolution in "Progressive" scan format) and 1080i (1080 lines in "Interlaced" format). There is currently no HDTV standard, and the various broadcasting companies are currently using one or the other system. (We will discuss "Progressive" vs. "Interlaced" scans shortly.)