Tuesday, July 15, 2014

K is for Keystoning

K is for Keystoning

Keystoning is a distortion of a projected image when the projector is not directed perpendicular to the screen.

          The keystone effect (or tombstone effect) is caused by attempting to project an images onto a surface at an angle. It is a distortion of the image dimensions making a square look like a trapezoid, the shape of an architecural keystone.

Common Solutions:

  • moving the projector more to the center of the screen
  • tilting the screen in a small angle
  • the use of special software on the projector
  • computer controlling the projector

          Keystone correction is the function that allows multimedia projectors that are not placed perpendicular to the horizontal centerline of the screento skew the output image, thereby making it rectangular. In modern projectors keystone correction technology is performed digitally via internal panels or mirrors of the projector, depending on technology used. 
          When applying keystone correction to an image the number of individual pixels used is reduced lowering the resolution and degrading the quality of the image projected. It is a useful technology in cases where the projector cannot be mounted directly infront of the screen, or on projectors utilizing lens shift technology where the projector must be mounted outside the frame of the screen.