 Both films are sandwiched together in the same camera and make use of a phenomenon known as "contact printing".The process had its beginnings in providing a repeatable method of compositing live action and matte paintings, allowing the painted section of the final image to be completed later, and not tying up the set/sound-stage whilst the artist matched the painting to the set.It also alleviated the considerable difficulties caused by matching shadows on the painting to the set on an open-air set.