It consists essentially of a camera (C) connected by a bellows (B) to a lens (L) aimed at a film in a gate (G) illuminated from behind by a lamp (I).
The camera and gate each have motorized intermittent film movements so that any frame of the “original” film can be conveniently photographed onto any frame of the “print” film.
The camera can be an ordinary cine camera, less its lens, and the gate can be an ordinary cine projector, less its lens. Ideally they have identical systems of film registration, as if one were the lens’ image of the other. The lens can be any bellows mountable lens. Ideally it is specially corrected for the small and nearly equal sizes of this object and image.
-The camera and the lens can slide independently to and fro the film gate. This adjusted the magnification and the focus of the photography.
+The camera and the lens can slide independently to and fro the film gate. This adjusts the magnification and the focus of the photography.
If the lens is (nominally) midway between the films when one is focused on the other, then the magnification is 1. At M = 1 (also called 1:1) the whole of the original frame is photographed at a size which fills the whole of the print frame.
Pictorially the zoom gets grainy, showing that it was not made in the original photography.
Rather than focus at each frame, camera and lens positions can be precharted for, say, every 10th frame, and the other positions interpolated or computed. On the J-K, counting the turns of the lead screw is a means of repeatable positioning. A follow-focus mechanism is a boon to optical zooms.
The rate and course of zooming is a factor of style, as it is in original cinematography.
- +For picture taking the printer lens should be at whichever aperture gives the sharpest pictures. This is found in tests. If a lens must be stopped down past f/8 to reach optimum it is a terrible printer lens.
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