Process Printer

(or optical-effects printer), an optico-mechanical printing device for the production of special effects.

A process printer is based on a motion-picture camera and up to four projectors. The film gate of the camera holds a motion-picture film, onto which an image may be projected from one or more negatives or positives. Combined projection of two images is accomplished either by placing two projectors at an angle to one another or through the use of a projector with two film gates positioned on the same optical axis. In the first case, the images are directed to the film gate by a beamsplitting system such as a pellicle mirror or prism; in the second, the image of the frame in the first film gate is projected onto the second film gate and, together with the image of the second frame, onto the film gate of the camera. Three or four images may be superimposed by combining the methods of projection superposition and by using a corresponding number of projectors. A combined image may also be obtained on a process printer by changing the relative position of the individual units and elements (the camera, projector, prism, and so on) or the direction and speed of the film, as well as through the use of various light filters.

A process printer makes possible the printing of special-effects frames using the traveling-matte method; it may also be used to enlarge or reduce an image. Changes in the speed, direction of motion, and position of the image and the printing of titles are also possible, as are wipes, panning across the field of an image, and tilting, turning, and rocking of the image.