Question: Which film director also appeared on screen as an actor, Dziga Vertov or Frederic Zelnik?
Sentence (from "Dziga Vertov"): Dziga Vertov (Russian: Дзига Вертов ; born David Abelevich Kaufman, Russian: Дави́д А́белевич Ка́уфман , and also known as Denis Kaufman; 2 January 1896 – 12 February 1954) was a Soviet pioneer documentary film and newsreel director, as well as a cinema theorist.
Relevant evidence: Yes