A Film Unfinished begins with archival footage of daily life in 1942 among the Jewish population of the doomed Warsaw ghetto. That footage, discovered in an East German archive at the end of World War II, had been recorded by Nazi filmmakers who were as obsessive in their cinematic ambitions as in their killing. But as director Yael Hersonski explains with dignified authority in her profound and vital documentary, those scenes of ''real life,'' once prized by historians, weren't so real. A missing reel, discovered in 1998, demonstrates the degree to which the Nazis manipulated the ''nonfiction'' they photographed, ordering residents to play roles in twisted scenarios staged to dramatize caricatured notions of the imprisoned residents, including the disregard of wealthy ghetto Jews for the wretched and starving. In these haunting outtakes, men and women who gaze at the camera speak without words. We see the skeletal living burying their dead in piles, and we see a Nazi officer filming the ''action.''
Hersonski quietly and insistently unravels reality from ''reality''; her commitment to archival authenticity is its own tribute to those no longer able to testify. And in this, she has a powerful aid: a few precious, elderly survivors of that infamous Warsaw ghetto who speak with her as they watch the same footage we do. Irrefutable truth-tellers, they recognize their neighbors. In doing so, they bring those streets alive again, for real. A