Fritz Lang’s landmark 1927 science-fiction epic has been shown in so many different versions, in so many different stages of “reconstruction” or outright revision (like the ’80s Giorgio Moroder reissue), that the only thing constant about it is its incomplete status. The 2010 release assembled from a near-complete 16mm print found in a Buenos Aires film archive is the closest yet to the 153-minute version that originally premiered in Berlin; by contrast, the version showing tonight is 25 minutes shorter — listed as 124 minutes, likely dating from the prior 2002 restoration. (Maybe that sounds nitpicky, but to film purists, it’s like a matter of whether you’d want more or less of a loved one’s life story.) Even without the additions, Lang’s vision of class revolt and mechanized dehumanization in a skyscraping dystopia of the future — inspired by the director’s view of the Manhattan skyline from New York harbor — remains one of the most eye-popping and influential films ever made. And in recent restorations, Eugen Schüfftan’s pioneering photographic effects — which use partial mirrors to combine swarms of actors and dazzling miniature sets within the same image — have never looked more impressive. The film shows tonight in conjunction with the Frist Center’s current exhibit German Expressionism From the Detroit Institute of Arts. The screening is free and open to the public.