"Caligari" and German Expressionism heavily influenced the American film noir period of the 1940s and '50s, both in visual style and narrative tone. Noir films tended to portray everyone, even the innocent, as the object of suspicion, a common thread in "Caligari". The genre also employs several Expressionistic elements in its dark and shadowy visual style, stylized and abstract photography, and distorted and expressive make-up and acting. "Caligari" also influenced films produced in the Soviet Union, such as "Aelita" (1924) and "The Overcoat" (1926). Observers have noted the black and white films of Ingmar Bergman bear a resemblance to the German films of the 1920s, and film historian Roy Armes has called him "the true heir" of "Caligari". Bergman himself, however, has downplayed the influence of German Expressionism on his work. "Caligari" has also affected stage theatre. Siegfried Kracauer wrote that the film's use of the iris shot has been mimicked in theatrical productions, with lighting used to single out a lone actor.