When the optics of a projectors lens is used to move an image up, down, left , or right on the screen.
A feature of a projector that shifts the optical lens in any direction to avoid keystoning and other anomalies.
The Lens Shift feature of a projector allows the optical lens to be physically shifted up and down (Vertical) or left and right (Horizontal). This allows for adjustment of the projected image.
Most projectors are equipped with lens shift to allow for the optical lens to be physically shifted up and down (vertical) or left and right (horizontal). Vertical len shifting is the most popular type of shift because it allows for keystone correction and assist in aligning images when multiple projectors are used stacked on top of one another.
The lens can be moved mechanically from the principal axis of a projector. Due to the change of the projection angle the keystone effect is minimizing. The greater the angle, the higher the loss of light and the greater the image errors (cushion - or barrel distortions).
Lens Shift: The Lens Shift feature of a projector allows the optical lens to be physically shifted up and down (Vertical) or left and right (Horizontal). Most all lens shift mechanisms are motorised with vertical lens shift being the most popular. With a projector that has lens shift you can optically correct for keystone distorted images. It is also used to help geometrically align images when stacking projectors.