A year or so ago Professor Marshall Deutelbaum of Purdue University, Indiana sent in a post devoted to the way production designers used the Cinemascope screen to organize the composition of the rectangular picture.
In Marshall’s words “Ages ago, artists discovered that every rectangle has two squares within it. Using either or both of those squares to organize the composition of a rectangular picture is called rabatment. Since the CinemaScope frame is also a rectangle, production designers knew they could use rabatment to define the proportions of movie sets for ‘Scope films. All that was needed, then, was for the cameraman to put the camera in precisely the right spot to capture the composition on film and for the director to position actors to energize the frame.
In these images, doorways, door frames, and the hard edge of a door clearly demarcate the interior verticals established by rabatment, though even soft curtains bunched together just right can serve the same design purpose. Rabatment encourages off-center compositions. Placing an actor on or close to one of the verticals enhances focus on him or her.”
Here's an example featuring below the rabatment grid of Deborah Kerr in Henry King's Beloved Infidel:
You can read the full post and get started delving into the subject if you CLICK HERE
Marshall has now made a presentation on the subject to the Society for the Cognitive Study of the Moving Image and has published an essay on rabatment which is now online and can be accessed if you CLICK HERE.