John Dominis, a Life magazine photographer who was known for capturing celebrities, wild animals and presidents at their unguarded best, and who was caught off guard himself while taking his most famous picture — of two American medal winners raising black-gloved fists at the 1968 Olympics — died Monday at his home in Manhattan. He was 92.

The cause was a heart ailment, said his daughter, Dori Dominis Beer.

Dominis was a star among a stable of star photographers at Life, the nation's most popular picture magazine, from 1950 until it ended weekly publication in 1972.

Ingratiating, self-effacing and ruggedly handsome, he was often assigned to photograph people who preferred not to be photographed.

He spent a month in 1963 with actor Steve McQueen (nearly feral in his aversion to publicity), who was not yet the superstar he became. And he persuaded Frank Sinatra to indulge him for three months in 1965 while he went inside his prickly circle of friends, family, drivers and body men to photograph his life.

It was not charm, though, but the reflexes of a professional photographer that helped Dominis produce his most enduring image.

On Oct. 16, 1968, when Tommie Smith and John Carlos ascended the Olympic podium in Mexico City to receive medals for finishing first (Smith) and third (Carlos) in the men's 200-meter dash — along with Australian sprinter Peter Norman, the silver medalist — Dominis was one of the few photographers who happened to be in the media pen 20 feet away watching and, he said, "expecting a normal ceremony."

After the athletes had received their medals and "The Star-Spangled Banner" began to play, Dominis was looking through his camera lens when Smith and Carlos, bowing their heads, each raised a gloved fist (Smith wearing the right hand and Carlos the left of a single pair of gloves) in a black power salute, to protest racism in American society.

"I didn't think it was a big news event," Dominis told Smithsonian magazine in 2008. "I hardly noticed what was happening when I was shooting."

The New York Times reported that the event "actually passed without much general notice in the packed Olympic Stadium."

Dominis later dismissed his black-and-white picture as "not much of a photograph." But it made the protest an indelible part of the iconography of the tumultuous 1960s.

Richard B. Stolley, a former assistant managing editor at Life and the founding managing editor of People, said Dominis was one of the most modest "great photographers" he knew, and one of the most poised.

"He had his finger on the trigger all the time," he said, while maintaining "a remarkable calmness."

John Frank Michael Dominis was born in Los Angeles on June 27, 1921, the youngest of four children of Paul and Mamie Ostoja Dominis, both immigrants from what is now Croatia. At Fremont High School, John studied under Clarence A. Bach, who taught a celebrated three-year course there that produced dozens of professionals, including eight staff photographers at Life.

Dominis studied filmmaking at the University of Southern California and was an Army combat photographer in Japan during World War II.

After covering the Korean War for Life, he traveled widely on assignments in Asia and Europe; covered President John Kennedy's 1963 trip to Berlin and President Richard Nixon's 1972 trip to China; and photographed the Woodstock music festival and five Olympics.

He spent many months in Africa for a 1966 Life feature, "The Great Cats of Africa," and later published several books of additional photos from the tour.

Though he worked as an editor and freelancer for other magazines in later years, Dominis considered Life the main event of his career. At Life, he wrote in an introduction to a 2007 show of his work at the Monroe Gallery in Santa Fe, N.M.: "I received all the support and money and time, whatever was required, to do almost any kind of work I wanted to do, anywhere in the world. It was like having a grant, a Guggenheim grant, but permanently."

Besides his daughter, Dominis' survivors include two sons, Paul and Greg, and seven grandchildren.