What is keystone correction?
Keystone correction corrects Keystoning. Keystoning is the rectangular distortion you get when your image appears wider at the top or bottom due the projector being positioned somewhere other than the center of the screen. Most LCD projectors today have a fixed keystone factor (allowing the projector to be placed at about an 8-degree angle lower or higher than the center of the screen), but many allow you to adjust keystoning. Thus you can place the projector on your conference table, on carts of various heights, or mount it on a ceiling of various heights without having to worry about ending up with a distorted image.
Keystoning is when your image appears wider at the top or bottom due the projector being positioned somewhere other than the center of the screen. Keystone correction, or lens shift, corrects this rectangular distortion. Most LCD projectors today have a fixed keystone factor (allowing the projector to be placed at about an 8-degree angle lower or higher than the center of the screen), but many allow you to adjust keystoning. Thus you can place the projector on your conference table, on carts of various heights, or mount it on a ceiling of various heights without having to worry about ending up with a distorted image.