NEW YORK -- Civil rights protesters in Birmingham cringing in the spray of a water cannon. A Vietnamese mother cradling her child and wailing as her village burns. West German youths smashing the graffiti-covered Berlin Wall. Chinese students pleading with soldiers not to harm the protesters in Tiananmen Square: photographs that have shaped the world's perspective of history.

These pictures have been brought into the public eye by a modest 68-year-old man who is actually not much of a photographer -- he shoots only a roll or two of film a year -- but whose work as a photo agent has given him a singular, if largely unsung, role in 20th-century journalism.

Howard Chapnick, who 50 years ago began working at the Black Star photo agency here as an assistant messenger boy, retired last week as its president, and the tributes have flowed freely. "He is Mr. Photojournalism," says photographer Charles Moore, who produced many memorable images of the civil rights movement. "I don't know if he can take a decent picture, but it doesn't matter. He's responsible for so many fine photographers."

Chapnick's stable of photographers has won heavy praise and more than its share of Pulitzer Prizes and other awards. He, by contrast, has served behind the scenes as a matchmaker, pairing up the photographer in the field with editors at newspapers, magazines and book publishers. Chapnick was known as a superb "idea man" who was sometimes able to persuade editors to run photo essays on subjects that were considered risky -- for instance, the American pacification program in Vietnam, the war in Nicaragua, or an intimate look at domestic violence.

"He wasn't going to peddle a bad idea," says Bob Gilka, director of photography at National Geographic from 1963 to 1985. "I've only worked with a few people in my career who never came up with a bummer idea. He was one. He knew the market too well. He knew whether or not this magazine or that one was going to go for a story. That's a tough racket, especially in New York."

On the first day of his retired life, Chapnick committed what he called a Freudian slip: He arranged to meet a reporter at his home but gave the address of the Black Star office.

For years the two have been almost synonymous. Black Star is a family enterprise of sorts. Chapnick's wife, Jeanette, is bookkeeper, while his cousin, Ben Chapnick, has now assumed the presidency after about 30 years with the agency. Longtime photo editor Yukiko Launois is a close friend.

When he started at Black Star 50 years ago, the son of a Manhattan grocer, Chapnick was just a flunky who needed a summer job. The agency, founded by three refugees from Hitler's Germany, had imported to America a technique known in Europe as the "picture story," an improvement over the single-picture approach then common in the United States. Co-owner Ernest Mayer took on the young Chapnick as apprentice, teaching him to pore over black-and-white contact sheets with a magnifying eyepiece known as a "loop" to select and crop photos for maximum impact. Chapnick eventually became aware of the power that came with the loop.

"I would get two contact sheets of Richard Nixon," Chapnick says. "I could make him an ogre by virtue of selection of the photograph. One has to be very careful ... to be fair. I don't think that because I didn't like Richard Nixon and what he stood for, it was in my purview to go out of my way to make him look bad."

Chapnick's formula for what makes an outstanding picture has been honed over thousands of hours at the light table. "I look for as much communication in the picture as possible," he says. "It should be technically good, show a strong center of interest, and use the frame from top to bottom, left to right, front to back."

"He helped raise the status of American photojournalism," Gilka says. "When he started, and when I started, newspaper photographers were looked upon as the low man on the totem pole in the city room. They had been copy boys, they didn't have any education, they were rough and ready. They certainly had a generally poor name.

"Howard emphasized the fact that ... there should be gentlemen among photographers. They had to be thinking people, there had to be a gentility and sensitivity in their approach."

The loyalty between Chapnick and his photographers is fierce. David and Peter Turnley, twin brothers who have documented the upheaval in South Africa, Eastern Europe and China, turned down an opportunity to roast Chapnick at his retirement party for lack of material.

"We end up going frequently to very obscure parts of the world where we're broken off from communication, where you oftentimes wonder whether anyone is thinking about you," says David Turnley, a photographer at the Detroit Free Press and winner of the 1990 Pulitzer for his photographs from Beijing, who has a distribution agreement with Black Star. "I have many times gotten back to a place where I can make a phone call, and the person I call is Howard. It doesn't matter what he may have been doing at that moment, but you're the only thing that matters, and he's as excited as you are about the work you've been doing."

Though he has left Black Star, Chapnick has hardly retired from photojournalism. Two days a week he'll be at the International Center of Photography in midtown Manhattan helping assemble a resource center to preserve the work of 20th-century documentary photographers.

Then there are the books. One is an instructional and philosophical volume he is writing based on his experience in photojournalism. The other is titled "An Encyclopedia of the Greatest Pictures Ever Told." He's planning it as a six-volume set.

There are, after all, so many great pictures. "Without photojournalism," he says, "without television and electronic journalism, we would never have come to the realization of what was happening in the civil rights movement ... the realities of Vietnam ... the famous picture of the suspected Vietcong being shot, the napalmed children running down the road, these are very moving photographs. ... So I've always believed and I still believe that these great pictures condition people to respond."