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Video and data projection

SXGA and 16:9 aspect ratios and projection screens

16:9, 4:3, 5:3 aspect ratiosYou should be aware that you need to think about screen aspect ratio if you plan to project SXGA computer graphics, wide-screen or HDTV video. The SXGA standard uses a 5:4 aspect ratio and wide-screen video a 16:9 ratio, while standard video, VGA, SVGA, XGA and UXGA use 4:3.

The three aspect ratios are shown in the drawing at right. Here we've sized the images so that the width is the same for each, which is the situation you'd have if you were using a native SXGA projector and a 5:4 screen. You can see that if you switch to a 4:3 image, it won't be quite as tall as the 5:4, and the 16:9 image is significantly shorter.

If, on the other hand, you start with a native 4:3 aspect-ratio projector and a standard video-format (4:3) projection screen, then switch to SXGA, you'll end up with fairly narrow blank areas to the left and right of the image. (Switching to 16:9, you'll still have blank strips at the top and bottom of the screen.)

If you start with a native 16:9 projector and screen, your image will stay the same height but get progressively narrower when you go to 4:3 and 5:4 images.

There are two ways to handle this issue.

1. Live with it. Choose the aspect ratio you will most often use and buy the screen to match. Da-Lite and Draper now routinely make 5:4 and 16:9 screens, though they are generally special-order.

Some projector manufacturers are making it easier to live with a single-format screen. Sharp's newest native SXGA projector, for example, gives you the ability to resize 4:3 formats to a 5:4 aspect ratio if you choose, thus making it possible to use a 5:4 screen for almost everything. Yes the image will be distorted, but the distortion is slight.

2. Buy a multi-aspect ratio screen. Da-Lite's motorized Horizon Electrol, for example, has borders that move to give you up to four different aspect ratios. You choose what you want and your supplier can program the screen. You can even set up an AMX or Crestron control system to automatically change the screen to match the computer or video source. This is an elegant, if more expensive, way to handle 4:3, 5:4 and 16:9 aspect ratio sources.

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