Shooting for "The Cabinet of Dr. Caligari" began at the end of December 1919 and concluded at the end of January 1920. It was shot entirely in a studio without any exterior shots, which was unusual for films of the time, but dictated by the decision to give the film an Expressionist visual style. The extent to which Mayer and Janowitz participated during filming is disputed: Janowitz claims the duo repeatedly refused to allow any script changes during production, and Pommer claimed Mayer was on the set for every day of filming. Hermann Warm, however, claimed they were never present for any of the shooting or involved in any discussions during production.