The effect produced when the image from an overhead projector is not square, but wider at the top than at the bottom. This distortion is produced because the angle of projection is not perpendicular to the angle of the...

Keystone correction, colloquially also called keystoning, is a function that allows multimedia projectors that are not placed perpendicular to the horizontal centerline of the screen (too high or too low) to skew the output image, thereby making it...