"Hurry up, get your goddamn little show going, I've got fish to fry!" That's the irascible, invincible 83-year-old Haskell Wexler, the legendary cinematographer, barking at his son Mark, who has come to make a film about the old man.

And the result is something far more than a conventional biography, in which a great personage is profiled, summed up, categorized, canonized and passed into history. The strength of "Tell Them Who You Are" is its honesty in showing how the younger man faces the protean force that sired him, cheated on his mother, called him stupid, despised his politics and yet through it all, somehow, still loved him. Possibly without meaning to, the younger Wexler has made a superb examination not of professional cinematography -- really, who cares? -- but of the eternal bad business between fathers and sons, and that terrifying moment when you learn that the man you thought was a hero is just another man.

Of Haskell Wexler's professional stature there can be no doubt. He has been nominated for the Oscar in cinematography five times, winning twice, for "Bound for Glory" and "Who's Afraid of Virginia Woolf?" He's got a tubful of other awards, was director of the '60s radical classic "Medium Cool" and has had one of those charmed lives of accomplishment, interesting friends, vivid adventures, all made the more pleasant by a large chunk of inherited wealth, which cushioned him from rough times and professional disappointments that might have shattered a man with fewer resources.

He's also a royal pain in the butt.

The son Mark doesn't shy from his dad's diva-like posturings and manner. He accepts his father's genius, as do the interviewees he features, and much of the great Wexler oeuvre is evoked. But that's never the point. Character is the point. The old guy is forever shouting orders, giving lectures, instructing how to do it better. In fact, one of the things Mark loves to do is subtly push his father's buttons, knowing that a rant, like a summer squall, will blow in from the west, roar for a few amusing minutes, then blow out to the east.

The funniest conceit is that Haskell is convinced he could make a better film about himself than Mark could (confirming his reputation as a cameraman who yearned to take over as director) and is continually making imperious suggestions. "This is where you cut!" "You can't just have talking heads, you have to show something!" He threatens throughout to refuse to sign a release form, which would of course destroy the film. He hectors, he belittles, he walks out. He curses like a sailor. And, clearly, he is used to being in charge and not at all sure he trusts his son.

And why should he? Wexler the elder is one of Hollywood's champion liberals, and his politics are an essential part of him. He cannot put them on the shelf, not even for a second, and is always seeing Republican conspiracies, corporate gambits, FBI initiatives. Mark, meanwhile, has managed to grow up as a conservative, and has essentially made a living by cozying up to the powers that be: He is proud to have directed a documentary about Air Force One for that wild-and-crazy outfit National Geographic, and displays pictures of himself with both Presidents Bush. In fact, one of the defter touches of "Tell Them Who You Are" -- the title comes from the elder's continual childhood advice to the younger -- is its subtle location of political orientation in the psychology of the family, not the plight of the masses. It suggests that Haskell was such a lefty as a rebellion from his extremely wealthy manfacturer father (he led a strike in his father's own factory!); and, conversely, that Mark himself is such a righty because he grew tired of his oppressive dad's sermons about those masses and their plight in the breakfast nook of a Los Angeles mansion. Wisely, Mark never pushes this, and indeed his restraint plays brilliantly against his dad's bombast throughout the movie.

In some respects "Tell Them Who You Are" plays on conventional documentary form to push deeper than might be expected. It uses the standard celebrity peer interview format -- Billy Crystal, Michael Douglas, Jane Fonda and directors Norman Jewison and George Lucas are among the heads that talk -- but young Wexler always pushes them toward revelation, and the revelations are not always flattering. The big issue of Wexler's career -- his firing from "One Flew Over the Cuckoo's Nest" -- is probed, and like a relentless Woodstein, the director punctures his father's delusion that the FBI got him fired to punish him for his radical activities. He got fired, in fact, because he tried to take over the picture and his work suffered from all his plotting.

There is also some surprising wisdom: Jane Fonda, for example, who was photographed by Wexler in "Coming Home" and in Vietnam in the documentary "Introduction to the Enemy," is extremely insightful about growing up as the child of one of "them": that generation of artistic genius-fathers who feared and hated emotional intimacy.

The son also confronts his father on the issue of Other Women, something about which sons always wonder but seldom find the courage to ask. He asks, only to uncover a melancholy cliche: an evasive, self-justifying standard-issue male disquisition in which the older man acknowledges messing around physically but not emotionally, a line that the betrayed spouse never buys, nor does the son.

It helps enormously that Mark has waited until he was old enough to make this film. He's 47, beyond anger and surprise. This isn't an incendiary screed, but more an expression of gimlet-eyed love. He's not buying any of the old goat's peculiar brand of self-aggrandizing manner, but still he loves him, warts and all -- or all warts, as the case may be. And the old fellow loves the younger one back, after his strange fashion. He doesn't approve, he doesn't support, but he acknowledges, he permits, and in the end, the two realize that all they've really got is each other.

Tell Them Who You Are (95 minutes, at the Avalon) is rated R for nudity and obscenity.

Cinematographer Haskell Wexler is the cranky, badgering subject of "Tell Them Who You Are," a documentary by his son Mark, right.