Lost books by great writers occasionally turn up but, in a literary context, "lost" usually means "not worth publishing in his or her lifetime". The history of photography, on the other hand, is constantly updated and rewritten as entire bodies of work - by EJ Bellocq, William Gedney and others - are discovered. Vivian Maier is the most recent and celebrated case: until her photographs came to light few people seemed to have any idea that she had even existed.
The same, of course, cannot be said of Dennis Hopper, though for chunks of his life people in close proximity to him - wives, friends and collaborators - experienced his existence as a frequently deranged threat to theirs. His mania found a perfect outlet, years later, when he invested the role of Frank with intensely psychotic charm in David Lynch's Blue Velvet. Former wife Brooke Hayward (the first of five, the second of whom stuck around for a total of two weeks) speaks tenderly and respectfully of him in the book accompanying the exhibition of her husband's "lost album" at the Royal Academy. She also remembers him as "a sweetheart" in Peter Biskind's book Easy Riders, Raging Bulls, but that was before she had her nose broken and became scared that he was going to kill her. Peter Fonda, producer and co-star of Hopper's directorial debut Easy Rider, was scared of him too. Not so Rip Torn who, when Hopper pulled a knife on him, twisted it out of his hand and turned it on his assailant. These violent episodes occurred before Easy Rider became a paradigm-busting hit.
Film critic David Thomson considers this success one of the biggest disasters in the history of cinema (on the grounds that "'youth' was given the kingdom - not just as filmmakers, but as the controlling element in the audience"). For Hopper the consequences may have been even more catastrophic. The accruing combination of enormous wealth, acclaim as a revolutionary genius, freedom from studio constraints and massive use of cocaine meant that he pretty much went gaga. Hopper claimed that Easy Rider put coke on the map of mainstream US, but for him it was just another ingredient in the mix of booze, speed, pot and acid that fuelled his progress from bohemian to beatnik to hippy to casualty of the counterculture of which he was an icon. He came back from an LSD love-in in San Francisco in 1966, Hayward recalls, with blood-red eyes, a ponytail and "one of those horrible mandalas around his neck". But well before that, before things fell apart, Hopper - exactly as prescribed by Yeats's poem "The Second Coming" and Joan Didion's famous essay "Slouching Towards Bethlehem" - was full of passionate intensity. Nicely photographed by Hopper as a man high on the cosmic importance of his mission, Timothy Leary provided the happy mantra of the 60s - "Tune in, turn on, drop out" - but the decade's epitaph was spoken by Fonda in Easy Rider: "We blew it."
The aftermath of Hopper's first film as director saw the global superstar on a self-exiled binge in Taos, New Mexico. Wrangling footage of his second, The Last Movie, into something approaching coherence while remaining true to shifting principles of incoherence proved predictably tough - not least for anyone expected to sit through the result. Hopper's banishment was by then complete, but it was not unprecedented. By the time Hayward gave him a camera for his birthday in 1961 he had already been booted off the set of From Hell to Texas and was effectively blackballed in Hollywood.
There were worse places to be out of contract. The LA art scene had just started to take shape and Hopper was in its midst as a collector (he bought one of the first Warhol soup-can paintings), participant, friend and witness. The history of photography is full of people who took to the medium because they couldn't draw (Fox Talbot for starters) so it made sense for the unemployable actor - who was also a painter and sculptor of enthusiastic but limited ability - to turn to the camera. As in a low-budget indie production, the nascent scene had a cast of dozens, some natives of this coastal paradise, others, like Hopper himself (Kansas) and Ed Ruscha (born in Nebraksa, raised Oklahoma City) from the mid-west. In opposition to the psychological depths plumbed by the New York-based abstract expressionists, LA art relished and reflected the mass visual culture of southern California. "Pop" may have been a conceptual import but its raw materials could be locally sourced. The streets were full of stuff that would end up in the paintings and photographs: cars, gas stations, billboards for the movie stars Hopper counted among his friends. They brought a glamour to the art which, in turn, celebrated the profundity of the superficial. The marriage of showbiz and art has been enduring; as merger it has proved stunningly lucrative.
A year after the first ever show of soup cans, at the Ferus Gallery on La Cienega Boulevard in 1962, Warhol returned to LA for another exhibition. Hopper, who had hung out at the Factory in New York, threw a party for the putty-faced maestro. "This party was the most exciting thing that had ever happened to me," Warhol recalled. "Vacant vacuous Hollywood was everything I ever wanted to mould my life into."
With the camera constantly around his neck, always snapping, Hopper's friends jokingly called him "the tourist" but he was, quite literally, at home among these artists, their creations (the walls were soon as crammed with art as a Paris salon) and the swirl of imminent happenings. As with Frank in Blue Velvet Hopper channelled this early version of himself as the camera-toting photographer at Kurtz's compound in Apocalypse Now, interrupting a crazed monologue to Martin Sheen with the image-addict's compulsion to score: "I wanna get a picture."
So although Hopper was in one sense an internal exile, the ability to stake a claim as some kind of outsider was fast becoming a requirement of admission and a sign of belonging, both in a local art scene freeing itself from the gravitational pull of New York and a movie business ossified by its own commercial might. More generally, since Rebel Without a Cause - playing alongside James Dean was the formative experience of Hopper's life - rebellion of one kind or another was emerging as a legitimate aesthetic option; Easy Rider would make it a fully institutionalised obligation. The urge was manifested most threateningly by biker gangs such as the Hell's Angels. Politically it was ennobled by the civil rights movement that reached a brutal climax in Selma, Alabama in 1965. Hopper was there for the third march, having been asked along by his friend Marlon Brando.
Hopper photographed all of this: artists, Angels, actors, marchers, and the streets (of Mexico as well as LA). Photographs of mini-riots in LA foreshadow escalating protests against the war in Vietnam, the sense of something not so much slouching as hurtling towards Bethlehem. So it bears stressing that these images have not ended up on the walls of the Royal Academy simply because Hopper was a famous actor who took a few pictures. He acquired a reputation as a photographer early on and was widely published before hanging up the camera in 1967. The retirement was sufficiently precocious that an exhibition in Fort Worth, Texas, in 1970 that might have served as a mid-career survey took on the character of a full-blown retrospective. "Without doubt", editors of The Lost Album insist, the work currently on show in London is the same as that in the Texas exhibition. The prints were selected by Hopper, attracted a lot of favourable attention - and were then lost: part of the flotsam and jetsam generated by someone swamped by the wake of his own legend. These vintage prints did not come to light again until after Hopper's death in 2010.
So what is his standing as a photographer now? How extensively does the history of 1960s photography need to be rewritten or reshaped in the light of this exhibition?
The answer requires some context. Robert Frank's book The Americans (1955-6) offered a radical reconception of what a photograph could be. A beneficiary of this legacy, Hopper didn't take photography into the realm where content almost overwhelms form, as did Garry Winogrand; he did not have the visual complexity of Lee Friedlander; nor did he have the obsessive eye of Diane Arbus. While he didn't invent or significantly extend a way of seeing he was fully articulate in the visual language of the time. As Fonda put it, he had an understanding "not just of the frame of the camera but the frame of the life".
And he had the simplest and most important gift of any photographer: he was there, not just in the same room, but on intimate terms with Warhol, beach-blond David Hockney and the strikingly handsome Edward Ruscha. We associate this kind of intimacy with Nan Goldin but whereas Goldin's photographs are like mirrors, recording their own historical importance, Hopper's are a source of biographical data about people who have helped make the world look the way it does. In them we can see not just history as it was happening but documentary evidence of myths in the process of formation. The value of such work only ever increases over time. In that regard Hopper's photographs seem more important now - when the dudes in them are either dead or grey-haired billionaires - than when they were taken. This is made more pronounced by the way the prints were lost from sight for so long, preserved like time capsules from another era.
The Selma pictures do not have the front-page power we expect of a world-historic event; they seem instead like fairly discreet souvenirs of a day in the lives of the people who were there. For a raging megalomaniac, Hopper had a surprisingly modest visual style.
The photographs of bikers may not have the immersive narrative power of Danny Lyon's contemporaneous The Bikeriders, but they are shot through with the "lost angel of a ruined paradise" thing that Shelley found in Keats. Coming from Kansas, having starred in numerous westerns, Hopper sees the Angels both as oily descendants of the cowboy-outlaws - and as a bunch of rednecks. One picture in particular, of an Angel and (as the argot of the tribe had it) his "old lady", performs a service which seems almost prophetically useful. Looking at a photograph by William Klein of some kids in New York Roland Barthes famously noticed - was "pricked by" - "one boy's bad teeth". This guy's mouth is half full of bad teeth. It's like he and Hopper, between them, pre-emptively knocked Barthes's idea of the punctum, the accidental detail, down his throat before he even got a chance to say what it was.
Among an impressive haul of pictures there are a number of masterpieces. A famous shot of bare-chested Paul Newman (1964) rendered calmly feminine courtesy of the fishnet shadow cast by a chain-link fence is one of the most gorgeous pictures ever of a man - and a naked demonstration of the actor's subtle knack for manifested interiority. And then there's the so-called Double Standards photograph used as a poster for a 1964 exhibition of Ruscha's gas station paintings: a self-captioning view of two Standard Gas station signs through a car windshield, with another car reflected in the rear-view and a glimpse of sky through the sunroof. So much photographic traffic converges here - Walker Evans, Frank, Friedlander, Stephen Shore - that if you had to distil 20th-century American photography into a single image you could do a lot worse than choose this one.
Dennis Hopper: The Lost Album is at the Royal Academy of Arts, London W1, until 19 October. Geoff Dyer's new book, Another Great Day at Sea, is published by Visual Editions.
Andy Warhol, Henry Geldzahler, David Hockney and Jeff Goodman, 1963
Double Standard, 1961
Paul Newman, 1964