The Goetschmann PC (Perspective Control) Adapter serves a dual purpose. To prevent screen image distortion (keystone effect) which would be caused if the entire projector would have to be tilted up or down, or slanted sidewise towards the screen. It also is used to precisely align screen images when two or more projectors are used.
The Perspective Control Adapter is placed between projection lens and projector housing and can be customer installed. The adapter permits the lens optical axis to shift +/- 8mm horizontally, + 8mm / -7mm vertically and +/- 8mm diagonally.
The Perspective Control Adapter can be used with all Schneider projection lenses - except Prolux "C" lenses - for perspective control and aligning screen images for multi-image shows.