Photographer Diane Arbus saw herself as a journalist first and an artist second, says her former editor, Peter Crookston – capturing all that was strange and mysterious on the streets of New York

Within her own short lifetime, the photographer Diane Arbus was widely acknowledged as a major American artist. Her work was shown, to great acclaim, in the New Documents exhibition at New York's Museum of Modern Art in 1967. Many of the images in the show were from magazine assignments, and from that year until her suicide - aged 48, in 1971 - she continued to take memorable photographs while working as a journalist.

Soon after that exhibition, I met her to discuss photographs we might buy from her, or assignments she could work on for the Sunday Times Magazine, where I was then assistant editor. She never mentioned the word art or artist in relation to herself, either at that first meeting, in any subsequent conversations, or in any of the many letters she wrote me. Her enthusiastic preoccupation was always journalism - picture stories we might produce together.

She had already worked on her own story ideas for Harper's Bazaar and Esquire in New York, and had begun her photographic career in collaboration with her husband, Allan Arbus, as a freelance fashion photographer for Vogue, Glamour and Seventeen in New York, so she was no ingénue. She was acutely aware of what would make a good magazine layout and she was not at all arty or neurotic about being cropped - as were, for example, Richard Avedon and Cartier-Bresson - if it meant her photographs might create more of an impact.

When I was editing Nova magazine in the late 60s and assigned her to photograph a gang of rockers - heavy-leathered bikers who were the violent rivals of sharp-suited, scooter riding and equally violent mods - she positively encouraged us to crop her pictures to make them look like family snapshots. "I thought of the Rockers as a sort of family album," she wrote. "If you'd like that you could crop them ... and maybe they [the Rockers] could write their own identifying comments under or across the pictures." It's hard to imagine any artist or photographer today so lacking in vanity they would encourage a layout idea above the interests of their own pictures. In the event we were so bowled over by her images that we printed them full frame in conventional double-page spreads, and she wrote that she liked the feature "really more than any published thing in a long time".

Her suggestion that we should monkey about with the photographs seemed all the more remarkable because she put so much effort into producing her superb large prints. She sometimes worked in her darkroom for four hours without a break, doing all her own developing and printing. In a letter after her trip to London in October 1969, she enthused about a new darkroom she had acquired, describing it as "heavenly, through an alley with its own anonymous door, like a secret house".

Arbus had an insatiable curiosity about people and how they live. As an artist, she wanted to convey an impression of these lives in her own particular way through the medium of her camera. She could do this by stopping people on the streets or in the park in New York, as she frequently did - but journalism gave her access to other, more intimate worlds.

"I've been working on an assignment which has opened a lot of doors I wanted open and it has got me going at a great old pace," she wrote in the winter of 1969. "It's about LOVE and it's for Time-Life Books so nearly nobody says no. I have found some 60-year-old twins who have always lived together and dress alike, a lady in New Jersey with a pet monkey who wears a snow suit and a bonnet, an incredibly heart-stopping handicapped couple (he is retarded and terribly tall and thin and she is radiant, maybe three-and-a-half-feet tall with curly red hair like Maureen O'Hara and tiny limbs and crutches). I saw them dancing at a dance for handicapped people."

Her passionate desire to see and record as much of life as possible was the reaction of an acutely intelligent woman who had endured a cosseted childhood cut off from reality in a huge, gloomy apartment overlooking Central Park. Her parents, David Nemerov and Gertrude Russek Nemerov, owned Russeks, a famous Fifth Avenue department store where Eleanor Roosevelt, Vivien Leigh and Mrs. Bob Hope were frequent shoppers. Two maids, two nannies, a cook and a chauffeur looked after Diane, her older brother, Howard, and her younger sister, Renée.

"We were protected and privileged as children," Howard Nemerov told Arbus's biographer, Patricia Bosworth. "But we were watched over incessantly. ... Everything in our home was based on approval, not love." He recalled that when their nannies took them for walks in Central Park, they were forbidden to remove their white gloves - even when playing in the sandbox.

They grew up during the Great Depression of the 1930s, but such was their insulation from the real world that Arbus told the oral historian Studs Terkel she had not been aware of the poverty, the soup kitchens and the long lines of people out of work looking for jobs. "The outside world was so far ... you were never expected to encounter it." In later life she said that the sense of being immune from that reality was painful; it had made her seek danger and excitement. "I've come to believe you can only really learn by being touched by something."

Her photographs seem to reveal that the little girl who was so repressed and isolated high above Park Avenue became filled with astonishment and wonderment when she came down to the sidewalks as a woman and saw the raw life of the city. She was fascinated by people living bizarre or even perverse lives, but she was equally drawn to ordinary subjects that other photographers might not notice - a teenage couple on Hudson Street, or a young man and his pregnant wife in Washington Square. To Arbus they were not ordinary, but novel, strange and mysterious; she saw them in the same way a child perceives things an adult cannot see. And we, looking at her photographs, experience something of that same eerie perception.

The excitement she felt prowling the streets of New York comes across in many of her letters. In May 1968 she told me:

"Lots is happening here and I live two blocks away from St Mark's Place, which has become one of the great corners of the city, where just standing still you feel in the heart of the maelstrom. The underground has a whole bunch of new heroes. There are some amazing flamboyant bewigged and empurpled whores who hang out on one particular place on Broadway and I have met a transvestite who says he has been one since he was three and who tells marvellous stories about the advantages of having a woman's job as opposed to a man's. I am also trying to do something on criminals, and maybe on returned runaways. Let me know [what you think] about all this."

Naturally I thought they would make, in her hands, excellent magazine journalism.

A photographer she greatly admired was the mainstream newsman Weegee, whose pictures of night-time scenes - murder victims, policemen, criminals, fires, car crashes - were the staple visual diet of the New York tabloids. Weegee (Usher, later Arthur, Fellig, 1899-1968) was the first New York photographer to get a permit for a police radio in his car so he could arrive at crime scenes simultaneously with the cops. But he also had a marvellous eye for the ordinary life of New York, photographing scenes such as lovers in a cinema, a family sleeping out on a fire escape during a heatwave, and children cooling themselves in the gushing water of a fire hydrant. His work was later published as a book, Naked City, which became a Hollywood film and the inspiration for a television series.

Arbus, who once wrote to me saying she was hoping to ride in a police radio car - "for crimes on long hot summer nights" - showed some of Weegee's photographs to her students in the photography classes she was teaching in 1965 at Parsons School of Design in Greenwich Village. She told her students she admired news photography because it was factual. In 1970, when she was asked by the Museum of Modern Art to help curate an exhibition called From The Picture Press, she tracked down Weegee's archive of 4,000 prints to the apartment of his former live-in lover. She chose many of his Daily News photographs for inclusion in the show, and by championing his work - "He was so good when he was good. Extraordinary!" she wrote - was instrumental in creating the impetus for a Weegee exhibition that went on a world tour and had immense success.

Arbus often wrote, with great style and lucidity, the accompanying text to her photographs. Her brilliant piece on Mae West for the American magazine Show in 1965 had an opening paragraph many magazine journalists today would be proud to have written:

On her seventy-first birthday Mae West feasted on a rhinestone-studded birthday cake. She is as Mae West as ever. Nourished by her own legend, she has outlasted every lover and initiated a nation of boys into manhood.

In the hot, humid summer of New York in 1971, not long before her death, when according to her friends she was in a deep depression, Arbus took a photograph of Germaine Greer, now anonymously captioned Feminist In Her Hotel Room NYC . "It developed into a sort of duel between us," Greer told Arbus's biographer, Patricia Bosworth, "because I resisted being photographed like that with all my pores and lines showing!" Arbus arrived at Greer's room in the Chelsea Hotel on a hot, muggy day and immediately asked her to lie down on the bed. Because she was so tired after the publicity tour for The Female Eunuch, Greer complied - but only up to a point. "I stiffened my face like a mask."

That Arbus was gaining a reputation as "the photographer of freaks" - a reference to her portraits of Russian midgets, a Mexican dwarf, a Jewish giant, a hermaphrodite - seemed to exacerbate her depression. She told friends that she felt she would always be known for these photographs, and she resented this label because she believed her portraits, at their best, suggest the hidden experiences that are within all of us.

Even when photographing babies, Arbus seemed to catch them at moments when their secrets - what they will look like as adults - are revealed. The anger and tension on the face of a child being held by its mother is a result of the stress of having been through a Diaper Derby, a race for babies in New Jersey, although these facts are not mentioned in the exhibition caption. Arbus suggested the derby as a story idea for The Sunday Times Magazine; it was one of the first features we commissioned from her.

On the whole Arbus enjoyed working with journalists, although on one occasion it was a disaster. We asked her to cover the wedding of President Nixon's daughter, Tricia, at the White House. Her photographs were not published, or publishable, because the president's staff placed her in an impossibly distant position from which she was not allowed to move, and she didn't use a telephoto lens. I still regret that we didn't print the long and amusing letter she wrote describing what happened, of which this is an extract:

The real old time newsmen who knew the score were working in teams with lenses the length of my arm and great enormous tripods and a kind of general unfriendliness which only meant that if they had to slit your throat later they didn't want to pal around too much in advance ... Meanwhile the reporters and the photographers were bickering because every time a guest ran the gauntlet, the society reporters would call out to them by name and ask what their dress was made of, so they would turn their heads away from the photographers at the crucial moment. There was only one crucial moment because you couldn't move out of this position you'd wangled, even though someone's elbow and someone else's umbrella were poking at you, because if you moved your space would get swallowed up...

No chance in that situation to make photographs from journalism that would end up on the walls of an art gallery. The images in her V&A exhibition and those in the books published since her death reveal that there was unquestionably great art in what Arbus produced with her cameras. But it was journalism - taking pictures of people for stories and getting their images on to a printed page - that nourished her art and resonated throughout her life.

The Guardian, 1st October 2005