A movie special effect named after its inventor, Eugen Schüfftan (1893–1977). He placed a plate of glass at a forty-five-degree angle between the camera and the miniature buildings. He used the camera's viewfinder to trace an outline of the area into which the actors would later be inserted onto the glass. This outline was transferred onto a mirror and all the reflective surface that fell outside the outline was removed, leaving transparent glass. When the mirror was placed in the same position as the original plate of glass, the reflective part blocked a portion of the miniature building behind it and also reflected the stage behind the camera.More HERE.
