But he loved taking photographs and they also brought home the bacon. For a long time they paid for the whole operation of the Factory. A major show featuring more than 300 portraits by Warhol, most of them never before exhibited in public, opens this week, allowing us to reacquaint ourselves with Warhol’s exuberant world of the 1980s. Selected by the show’s curator, Anthony d’Offay, the images have been sitting in print form since the artist’s death in 1987 in the Andy Warhol Foundation in New York. There are tens of thousands of other Warhol photographs in the archive and this enormous show merely skims the surface of that extraordinary stash.

The photos reek of the hedonistic Studio 54 whirl and Manhattan underground art scene that Warhol became so associated with: here are Diana Ross, Bianca Jagger, Truman Capote and Sly Stallone packing a pair of skimpy swimming trunks very nicely indeed. There are club kids, drag queens and a cute punk wearing a six-pack, tutu and come-hither smile. And Jerry Hall, naturally. The reason there are so many photographs is that Warhol took his camera everywhere during the 1970s and 1980s. This was a fabulous era for the denizens of New York’s disco and club society and everyone made a huge effort to be fabulous everywhere and at all times. Warhol was there to capture them with his camera. It was a shamelessly pretentious and self-indulgent life.

“He loved taking photographs because he found it easy,” recalls Glenn O’Brien, a friend of Warhol’s and a colleague in the 1970s on Interview magazine. “Also, working with a camera was part of his philosophy of wanting to be a machine. He worked out how to make art mechanically, manufacturing it with machines as if it were soap. He eradicated the human hand.”

Warhol also loved taking photographs because his camera was a useful social crutch for one inclined to stare. The camera was to Warhol as sunglasses are to Anna Wintour. It let him be a voyeur and to stare unreservedly. It was also his way of flattering people. When celebrities were approached by Warhol at night clubs and parties, and had their pictures taken by him, it made them feel important. Warhol was a legitimate celebrity himself, and a portrait by him was a thing to aspire to.

And for all his social climbing and posing, his unabashed vanity, his tacky courting of beautiful kids with talent and trust funds, beneath his absurd pretensions and lack of seriousness, Warhol emerges as a very good, very acute photographer.

O’Brien says: “For years he had watched Bailey and Avedon and Diane Arbus, Robert Frank and others taking photographs. And then there were people like Stephen Shore, Nat Finkelstein and Billy Name shooting around him and the kids at the Factory. He was fired not only by ambition. He was also driven in some ways by jealousy. He always wanted to be as good as Bailey.” He probably was.

As disco society took hold of New York, Warhol began taking his colleagues from the Factory out to parties every night. Armed with his camera and with a tape recorder (which he called “the wife”), he shot all night, gathering thousands of frames. “I used to get dragged along to these parties by him,” O’Brien says. “I remember him once saying, ‘This is such hard work.’ It never occurred to me that going to parties could be considered work. But he saw his whole existence as work. With his camera and his recorder, he could extend his working efforts into the night, and if he found himself in an interesting place he could usefully exploit it as work.”

Warhol’s approach to celebrity snapping was different from that of the paparazzi, men such as Ron Galella. They were fighting to get in past the bouncers, but Warhol was already an insider. He had a licence to shoot anything he wanted and knew the whole crowd. He often went out partying with Bianca Jagger and Liza Minnelli, and would bump into Bob Dylan, Mick Jagger or Debbie Harry. Usefully, these were also the rich types who collected his work.

As an artist-socialite, he created a new kind of celebrity photography. While most subjects are immortalised as images of mute beauty, sometimes he felt like demystifying things. He had a mischievous streak in his photographic work just as he had in his diaries.

“My idea of a good picture,” he wrote in the introduction to his photographic book, Exposures, “is one that’s in focus and of a famous person doing something unfamous. It’s being in the right place at the wrong time.” As O’Brien says, Warhol loved to see the stars looking radiant, but every so often he also loved to see them looking rotten. And he had abundant skills to capture them.

Warhol’s World, Hauser & Wirth, London W1 (www.ghw.ch 020-7287 2300), Jan 27-Mar 11.