Optical printing technique for motion blur simulation — multiple exposures of single frame with offset positions. Creates high-speed effects without slow-motion capture.
Before the digital revolution, those who needed high-speed effects without actually shooting at higher frame rates resorted to the Borchmann process—an optical printing technique that creates motion blur through multiple exposures of a single frame. The method is simple: a subject is exposed multiple times, each exposure slightly offset from the previous one, all on the same piece of film. The result is a single frame with baked-in motion blur, conveying the impression of extreme speed—without the scene actually having been filmed in slow motion.
Practical Application in Optical Printing
In the editing room—which was analog at the time—it worked like this: The original film was loaded into an optical printer. The cinematographer or effects technician would position the image, make a partial exposure on the print material, shift the original by a few millimeters or frames, and expose again. Five to ten exposures were typical. The closer the offsets were, the smoother the motion lines appeared. The process required precise manual work—a tolerance of a tenth of a millimeter could become visible. Anyone who messed up this job had to discard the entire print.
The Borchmann process was frequently used for effect shots: bullets whizzing across the screen, exploding objects, lightning-fast cuts between positions. This characteristic motion blur was particularly seen in science fiction and action films of the 1970s and 1980s when the budget for a true high-speed camera was insufficient or when timing needed to be more precise than real-time footage allowed.
Limitations and Successors
The major disadvantage: the process was time-consuming, expensive per frame, and uncontrollable if the exposure was set incorrectly. With digitization, the technique became redundant—motion blur is now a filter effect that a VFX artist applies to any clip in seconds. However, understanding old film techniques also helps understand why modern motion design possesses certain optical qualities. Some colorists and VFX supervisors still refer to the Borchmann principle when discussing how natural and filmic a digital motion blur should appear.