Pornography and the mainstream movie business have always had a closer and more complex relationship than the latter would care to admit. After all, the technology used is much the same in both cases, and porn often seems to function as the sleazy shadow of the mainstream, a huge multi-billion dollar industry that respectable people don't like to talk about too much. Not surprising, then, that Hollywood has always avoided tackling the subject head-on, with a few notable exception, like last year's Boogie Nights.
Joel Schumacher's new film, 8mm, has none of the cheerful insouciance of Boogie Nights, the director agrees, although he admits there are parallels with Paul Schrader's movie, Hardcore. "That's the only film I could think of that approached this subject in the same way, and it certainly invites comparison. I think, though, that the George C. Scott character in Hardcore entered what I think of as the Boogie Nights world, which is mainstream pornography. "This stuff in 8mm is illegal; it's not the stuff with the pretty blondes with the fake breasts which you can find in the local adult video store, or on cable in this hotel. This deals with children, animals, torture, rape, atrocity . . . where sex fades away and power and violence take over."
In 8mm, Nicolas Cage plays a private eye employed by an elderly widow to investigate a small reel of film she has found in the personal possessions of her recently deceased husband. The footage seems to show a young girl being tortured and killed in a sado-masochistic ritual, and Cage sets out to find out who the girl was, and who made the film. His investigations take him into the netherworld of the Los Angeles pornography industry, where he finds himself appalled and fascinated by what he sees.
"You can't research this subject very much," says Schumacher. "Because people who do illegal things like that aren't going to come out of the woodwork to tell you about it. "Some of the people you see in the scenes in the sex club have worked in these films, and they knew a lot about the subject. But we created almost everything ourselves, because there were things I just didn't want to show."
Given his reputation as a stylist, though, it's hardly surprising that Schumacher's depiction of the hard-core world seems glamorised at times. "Well, once you get into that world of deviation and perversion, there are elements that are seductive and fascinating," he says. "I don't know who could walk through a sex club and not be interested in someone or something, even if it's just out of curiosity. "It's not like walking through an illegal weapons plant. We are flesh, and we have lust and an attraction to other flesh. It would have been dishonest to show Nic as a boy scout, who is pure and doesn't find any of it attractive. "But I tried hard not to glamorise it, because it's very easy to glamorise sex and violence on film, so I tried to make it as sordid and seamy and evil as possible.
"In my movie, one character says that these things won't last much longer, because it's all on the Internet now, but I think people will always like the thrill and the danger of actually going to these places, of looking at all this stuff and touching it. "Also, the Internet is getting more regulated, and I think it will start getting busted more. People who are into serious perversion will always find a way.
There's a weird tension in 8mm, I suggest, between Schumacher's stated desire to paint a relatively naturalistic portrait of this grimy world and his own tendency towards the hyperreal. After all, his last movie, the much-reviled Batman and Robin, which he himself describes as "a nightmare" is a long way from the hard-core industry (although there is a shared interest in latex and rubber). Casting Nicolas Cage, Hollywood's most over-the-top A-list star at the moment, as the quiet, happily married central character, immediately taxes the audience's suspension of disbelief.
"Well, I think Nic became an A-list movie star the way I became an A-list director, sort of by accident. We were both doing interesting work but not breaking any records, just doing well. "Then we woke up one day and people were saying, `Oh they're A-list'. But I agree with you, I think he's totally off the beaten path and not at all like the standard movie star guy. "I needed someone who would be fearless, and wouldn't worry about his vanity, or how his hair looked. Both Nic and I have done flashier work, and we both wanted to do something more low-key, about a relatively normal, quiet person. "I've never made a movie where I followed just one human being moment by moment. Usually I do ensemble pieces - even with Falling Down, people forget there's an hour of Robert Duvall mixed in with an hour of Michael Douglas's brilliantly extrovert performance."
Falling Down, Schumacher's film about "white male rage" as personified by Michael Douglas's violent rampage across Los Angeles, was the director's most memorable movie so far, in a filmography which ranges from the campy horror flick The Lost Boys to the John Grisham adaptations The Client and A Time to Kill. Like 8mm, it offers a highly jaundiced view of life in Schumacher's hometown of Los Angeles, with the porn industry as a distorted mirror image of the mainstream movie business. "So much of American porn is made in California, and in the San Fernando Valley in particular," he says. "There are between 750,000 and a million missing people in the US each year. Beyond that there are around a million runaways. What happens to all those people - where do they go? Runaways a lot of the time will gravitate to big cities with unrealistic dreams of what's possible."
Of course, there's nothing new about all this. Schumacher draws comparisons between his own film and the US's most famous unsolved murder case, the Black Dahlia murder in Los Angeles in the 1940s. "There's a really good new book out called Severed, which seems to me to have solved that crime, and it's so much the same story as the girl in my movie. "She doesn't get on with her mother, they fight all the time, she leaves, goes to LA with these dreams of getting into the movies, gets involved with the wrong kind of man and winds up tragically butchered in the middle of a field. "And here we are, 50 years later, and you can have exactly the same story, because these runaway kids are perfect prey for the pimps, the pornographers, the perverts and the drug dealers.
"They have this fantasy of Hollywood, but there is no Hollywood, it's a myth that exists in our heads. There's a handful of movie studios, spread out over a huge city. "There's Hollywood Boulevard, which is so sleazy you wouldn't believe, filled with runaways and drug addicts and chicken hawks and crazy people. "So there you are, on the Walk of Fame, and as you step over the crack addicts sleeping in the doorway and the teenage hookers and the guy puking up from an OD, you see Liberace's star or Dr Ruth's star or whatever.
"Hollywood is always presented with these gorgeous blondes, Venice Beach and Baywatch and all the rest of it, but that isn't how it appears to me. There's this terrible blaring sunlight, and that ugliness and the despair.
"That's the dream, not that silly sign up in the hills. But these kids keep arriving, because it's still the only place you can become famous overnight, with no training and in some cases no talent."
8mm is on general release.