SAN FRANCISCO (Bloomberg) — Dressed in a black sequined dress with a plunging halter neckline, her curly blond hair and bare shoulders highlighted against a simple gray background, Marilyn Monroe gazes off to the side with a look of world-weary exhaustion.

Richard Avedon's startling 1957 portrait of Monroe captures both her sexiness and her vulnerability. It's one of more than 200 iconic images in the first major retrospective of Avedon's work, now at the San Francisco Museum of Modern Art.

The Monroe portrait, though early in his long career — he died in 2004 — has all the hallmarks of Avedon's serious work. She's posed before a studio backdrop, stripping away the clutter of a real-world environment. The camera focuses intently — almost cruelly — on every surface detail. Avedon captures a moment, in Monroe's sideward glance, that seems to reveal personality and character.

The exhibition covers almost six decades, from early fashion work (a curvy Balenciaga suit paired with a troupe of street acrobats in 1948 Paris) to his merciless later portraits, with lots of celebrity shots from the '50s and '60s in between (Bob Dylan in a leather trench coat, the Beatles, a creepy, wall-size series of Andy Warhol and his partially clothed sidekicks from the Factory).

One gallery displays all 69 images from "The Family," Avedon's bicentennial view of the US political establishment commissioned by Rolling Stone (a stolid President Ford, his successors Carter, Reagan and Bush, a sour-looking Hubert Humphrey, a shark-like Donald Rumsfeld).

Avedon's later work is even more hard-nosed. "In the American West" of 1979-84 shows roughnecks and drifters, coal miners and dirt-poor farmers — each standing before the same sort of studio backdrop as Monroe did and photographed like movie stars, some looking downcast, others proud to be surviving. A portrait of a 13-year-old rattlesnake skinner in Texas holding his latest victim delivers a jolt.

Robert Frank's photo essay "The Americans," published in the US 50 years ago, captured a darker view of the country than the typically uplifting imagery found in the pages of Life magazine. The book changed "street" photography forever, and another exhibition at SFMOMA shows why.

Travelling across the US in 1955-56, the Swiss-born Frank captured the nervous energy of the time, sometimes using blurred or off-kilter images to convey how things were changing. We see New York socialites at a museum reception and black leather-clad bikers on the road.

His portrait of the city fathers of Hoboken, New Jersey, decked out in long coats and top hats on a parade-viewing stand, conveys their complacency and vanity rather than their patriotism, and it's a classic.

The spacious installation shows all 83 black-and-white pictures in the book in large vintage prints that reveal more details and subtle greys than the images in the book itself. There's also a gallery of Frank's early work in Paris and London, plus a selection of work prints and contact sheets that show how he assembled the book from thousands of shots.

The third part of SFMOMA's triple-header in photography this summer is "Georgia O'Keeffe and Ansel Adams: Natural Affinities," an apt pairing of O'Keeffe's colourful, almost abstract New Mexico landscape and flower paintings with Adams's photos of much the same territory.

The two artists became friends in Taos, New Mexico, in 1929 and it's not hard to see how they both loved the elegantly desolate deserts and mountains of the area. The surprise in the roughly 100 works on display is how easily Adams's black-and- white photographs stand up to the larger, pastel-coloured paintings by O'Keeffe.

"Richard Avedon: Photographs 1946-2004" runs through Nov. 29 at SFMOMA, 151 Third St., San Francisco, +1-415-357-4000; http://www.sfmoma.org.

"Looking In: Robert Frank's 'The Americans'" runs through August 23 at SFMOMA and will be on view at New York's Metropolitan Museum of Art from September 23 to January 3.

"Georgia O'Keeffe and Ansel Adams: Natural Affinities" runs through September 7 at SFMOMA.