“Hogan’s Heroes” remains a significant piece of television history for its injection of humor into the unmistakably unfunny setting of World War II. “Auto Focus” comes full circle, illustrating the personal darkness and tragedy of the life and mysterious death of Bob Crane, “Hogan’s” eponymous colonel.

The film follows Crane — played convincingly by Greg Kinnear (“As Good as it Gets”) — from his pre-Hogan days as a Los Angeles disc jockey through his successful television years and the decline that followed, right up to his death in an Arizona motel room in 1978. It is a story of personal collapse brought on by fame and excess.

Crane begins as a happy, aspiring actor and family man, married to his childhood love, played compassionately by Rita Wilson (“That Thing You Do”). A stash of pornographic magazines in the garage and Crane’s interest in “photography” are the only early signs of his proclivities.

Enter John Carpenter. No, not the horror guy. This John Carpenter is much scarier. Willem Dafoe (“Spiderman”) plays the slimy A-V technician who hooks Crane up with prototype video gear, introduces him to a world of strip clubs, swingers and starstruck groupies, then becomes his lackey in sexual exploits and exploitation.

If not for easy comparisons to his deliberately cartoonish Green Goblin, there would be no shortage of praise for Dafoe’s portrayal. This villain is more subtle and real, but Dafoe’s built-in sneer might hereafter always hearken back to “Spider-Man.”

Kinnear, meanwhile, transforms his character into a sexually obsessed has-been with equal subtlety. The film itself is filled with hints at Crane’s fate and many an ironic line to clue us in or give us a cynical smirk. At times it becomes too much — how can so much subtlety fail to become less than subtle?

The strong performances render simplistic metaphors unnecessary, yet still director Paul Shrader (“Affliction”) feels the need to show us that going to church equals “good,” and drinking alcohol equals “bad.” The film works best when we are convinced that Crane and Carpenter see themselves as normal, and we are allowed to make our own assessments.

Visceral scenes of the collapse of Crane’s two marriages are conspicuously absent. The film creates distance between Crane and his confidants as his sexual escapades become his central concern. This contradiction of intimacy is what makes “Auto Focus” successful.

The title is a throwaway, better suited for a film about an optometrist from Detroit. The posthumous voiceover detracts from the film’s reality, which is otherwise convincing. The backdrop of ’70s singles-bar culture is frighteningly believable.

The best moments of the film are the recreations of “Hogan’s Heroes” shoots, which become a darkly hilarious representation of Crane’s descent into moral bankruptcy. There is a sense of humor in “Auto Focus” which keeps it from trying to preach about “the evils of pornography.” It is about one man’s corruption and his demise, which is made less mysterious by this biography.

Grade: A/B