Lens Shift Control allows a fixed-pixel front projector to mechanically reposition the lens in relation to the screen. Lens shift is indispensable in situations in which the projector cannot be mounted within the ideal range as specified by the manufacturer.
background, CRT front projectors traditionally have provided a keystone
control that allows the installer or user to compensate for geometry
errors that result from less than optimal positioning of the projector
in relation to the screen.
While a form of keystone control is typically provided on most
fixed-pixel projectors, using keystone correction will undermine 1x1
pixel mapping, an essential property for any type of digital display.
Enter Lens Shift, which provides a solution to projector placement
challenges, usually with relatively minor sacrifice in performance.
However, there is a limit to the degree of lens shift that is
available with any given projector, and more importantly, even where
sufficient lens shift range exists to address severe placement
problems, excessive use of lens shift can introduce visible image