Quick, who is the greatest female movie director? Once there was an easy answer to this acutely sexist question, given by critics as different as John Simon and Pauline Kael. Stephen Bach's new biography, The Life and Work of Leni Riefenstahl, assures us that Riefenstahl's eye as a director and her persistence as a filmmaker once overruled questions about her content.

Such was the case as far as film festival programmers were concerned. One London cinéaste put it that "Satan himself is welcome at the National Film Theater, provided he makes good pictures." And Riefenstahl wasn't Satan. She merely worked for his lieutenant on earth, Adolf Hitler.

Years after making her most significant film, Triumph of the Will (1935), Riefenstahl obscured her devoted aid to the Third Reich. In one particularly deft wiggle, Riefenstahl and her lawyers sued a documentary maker named Nina Gladitz, who claimed that some of Riefenstahl's extras in her later film Tiefland were sent to Auschwitz after she was done with them. In fact they were sent to a different death camp, and on those niggling grounds, Gladitz had to delete the sentence from all videocassette copies of her film, an expense she couldn't possibly finance.

Now that Riefenstahl is dead, Bach can lay out all of her lies, obfuscations and lapses of memory.

A dancer by inclination, the Berlin artist moved into the milieu of Germany's Alpine Film, famous for its cinematic celebrations of hiking and skiing, which opposed studio-based German expressionism in the same way that your aunt's plein air painting opposes modern art. On the whole, they're kitsch with splendid landscapes.

Riefenstahl, whose physical bravery outweighed her moral bravery, did her own stunts. The films caught the interest of Hitler, and she soon became his court documentary maker. Some have claimed she was Hitler's lover as well. (Bach thinks not; as always, Hitler's interests were elsewhere.)

Like all of the best film books, Leni describes the times as well as the largest figures in the landscape. Bach's writings on the Weimar Republic are concise and affectionate. He retrieves innovative figures from the clutches of credit grabbers. His passage on Dr. Arnold Fanck, father of the Alpine film, is as useful a corrective to the idea of Riefenstahl as a solitary genius.

Not only is Leni a study of how Riefenstahl adapted the Third Reich for the screen, but it is also an essay on the problem of whether a really good eye justifies a diseased comprehension of the world. "One cannot live an honest life in the service of the false," judged Germany's culture minister Christina Weiss when Riefenstahl died at age 101 in 2003. Bach called Leni the oldest functioning filmmaker; I'd argue the 99-year-old Manoel de Oliveira has her beat.

And to answer the sexist question in the beginning: Agnes Varda? The Gleaners and I doesn't have the same visual distinction as Triumph of the Will, but it has everything that Riefenstahl leaves out of her work: a joy in the heroism of ordinary humanity, as opposed to Riefenstahl's love of demigods. Varda's Vagabond takes a reverse angle on the scrounging life, showing that Varda is no silly romantic. Even the synopsis of Varda's pioneer New Wave film Cleo From 5 to 7 is more mesmerizing than Riefenstahl's scuba-diving footage--referred to by Nazi cinema expert Eric Rentschler as "Triumph of the Gill."

Riefenstahl's filmmaking represents a technical triumph, as brilliant as the autobahn or the VW. Her best work can be seen in Triumph, where she observes the transubstantiation of Hitler with multiple cameras and improvised cranes made out of flagpoles. Her aerial photography of der Führer's plane landing is as delicately engineered as a great screen kiss. No one could have better solved the technical challenge of making a commercial for Hitler. Her innovative crowd scenes turn humanity into the man-machine.

Thus she was influential in the only kind of cinema that could appreciate such a transformation: science fiction. George Lucas has acknowledged how these Nuremburg shots were adapted into Star Wars: the gleaming formation of imperial storm troopers waiting their wheezing, black-helmeted Führer. For that matter, there's also a lot of Riefenstahl in rock-concert movies, and her still-revived epic documentary on the 1936 Olympics, Olympia, was a breakthrough for sports photography. Bach describes in detail how Riefenstahl put cameras everywhere, even around the necks of the marathon runners and in trenches to get a ground-eye view (in fact, Jesse Owens almost broke an ankle in one ditch).

As many commentators have pointed out, what's brilliant in excerpt is dull at length. For all their invention, Riefenstahl's documentaries address us as if we were at a public meeting. "When a director dies, he becomes a photographer," says the proverb; this fate befell Riefenstahl even before she really died.

Leni: The Life and Work of Leni Riefenstahl by Steven Bach; Knopf; 386 pages: $30.

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