Sin City, the intensely brutal cult comic, has been turned into an intensely brutal movie. The graphic artist and film director team talk to Donald Clarke

Frank Miller, the comic-book artist and writer who humanised Batman and saved Daredevil from the dole queue, is mouthing off. "I think the relationship between comic books and film is improving," he says. "It’s a marriage, but for a long time that marriage has needed counselling.

Comics were walking around like this abused child or this battered wife and something needed to be done about that. I hope that Sin City has changed things. Suddenly one of my tribe is directing and that's important."

Sin City, a pummelling, relentlessly visceral adaptation of Miller's similarly titled series of graphic novels, looks and feels like no previous comic book movie. Created from large, inky blocks, this compendium of noir fables, on which Miller shares a director's credit with the DIY maestro Robert Rodriguez, shows a degree of respect to its source material that Hollywood more usually accords big fat books on the US civil war.

There have been attempts to engage cinematically with the grammar of the comic before. Ang Lee's Hulk –we're still not sure if it takes the definite article – experimented with multiple frames and played with text in a manner that was alternately intriguing and irritating.

But there was something literalminded about these flourishes; they reminded you of movie directors who begin theatrical adaptations with the titles displayed beneath a proscenium arch.

Sin City, made for under $50 million (139.73 million) with a cast that includes Bruce Willis, Mickey Rourke and Jessica Alba, translates the images from Miller's books onto the screen with striking fidelity. It is a stunning achievement, though some may wonder if it is a film director's job to replicate the source material quite so slavishly. Transferring a story from one medium to another should require some moulding and adapting. Shouldn't it?

Rodriguez, a polite, unflappable Texan, dressed today in a cowboy hat and hazelnut coloured suit, nods patiently as I play devil’s advocate.

"I just felt this was so much bolder than anything we were doing in cinema right now," he says. "It was originally created as an anti-movie. Frank did it as a reaction against Hollywood. Here was this book that couldn’t be adapted as a movie. It has dialogue that doesn’t read like screenplay dialogue and I looked at this and thought, I really cannot improve on this. If I changed it I would just be changing it for the sake of changing it."

In the early 1990s, Frank Miller had had enough of the movie industry. After writing and drawing his hugely successful The Dark Knight Returns, in which an ageing Batman comes out of retirement, Miller had, perhaps inevitably, been lured to Hollywood.

He took meetings. He wrote RoboCop 2. He took some more meetings. He wrote RoboCop 3. He took yet more meetings. And, all of a sudden, he wasn't a comicbook guy any more.

"I want to make clear that I was treated perfectly well in Hollywood," Miller, a ruddy man with a knobbly nose, drawls. "But I was used to being my own boss and suddenly I am in this industry where it takes tens of millions of dollars to do anything. So I decided to write the comic I had always wanted to write as a kid."

Sin City, published by the admirable Dark Horse comics, was the result. Telling the story of brutish, flawed men who meet terrible fates because they love curvy women, the series managed to combine the techniques of Japanese Manga with the ambience of darkest American noir pulp. The novels of Mickey Spillane and James Ellroy are in here, as are the films of Robert Aldrich and Raoul Walsh. "There were a series of rules in terms of content," Miller says. "I always write these things down. I wrote myself a rule book: all the guys had to be rough looking; all the cars had to be vintage; all the girls had to be gorgeous.

After that it got down to method and technique." Having drawn the book as a reaction against Hollywood, Miller was, understandably enough, cautious about embarking on a film adaptation – "Oh, I was adamantly opposed to the idea."

But Robert Rodriguez, who famously made his first feature, El Mariachi, for a reputed (and disputed) $7,000 (15,566), is one determined fellow. Based in Austin, Rodriguez shoots, edits and scores all his own films. Post-production takes place in his garage. He felt sure he could put together footage that would convince Miller his intentions were honourable.

"Yeah, he phoned me up and said: ‘I can do a test of this one scene in a day’," Miller explains. "And I looked at the script and thought: there’s three pages here; he can’t do that in a day. But he had said he’d shoot it with a couple of friends or whatever, so I flew on down to Austin. Turns out his friends are Josh Hartnett and Marley Shelton, and the scene he shot was the first scene you see in the film. It looked amazing. I thought: Test nothing. This is the first day of principal photography.’"

Miller was on board. But Rodriguez wasn't happy for Sin City's creator just to lurk around in the wings. He was adamant that Miller should become co-director.

The Texan has never played the Hollywood game and, not for the first time, he found himself antagonising powerful forces. Some years back, angered at the regulations imposed on the allocation of screenplay credits, he huffily left the Writers Guild of America.

Now that body’s sister organisation, the Directors Guild of America (DGA), which insists that only one director per film be credited, began kicking up a fuss.

"There are two directors on lots of movies," says Rodriguez. "That wasn't a problem. This was just about him receiving the credit. I think that on Lord of the Rings they actually had six directors working with actors. They didn't want the situation you have with writers, where you get four or five credits and it's meaningless.

"And, actually, part of the reason I wanted Frank to get a director’s credit is those writer credits really don’t mean anything any more. I thought this was a special case, but I couldn’t get the DGA to agree. So we decided it would be simplest if I left the guild."

That sounds amicable enough. "Well, I called them a bunch of old farts. Aside from that it was amicable." Sin City also features a "guest director". Rodriguez' old pal Quentin Tarantino – screenwriter and star of the Texan's From Dusk Till Dawn – saw the test footage and was eager to helm a scene. "He had just come off Kill Bill and it had taken much longer than he had expected and I kept saying: 'That wouldn't have happened if you just shot it digitally. Just come down and see how easy this is.' So he was happy to give it a shot."

Rodriguez proudly explains that by simply typing out the dialogue from three of the Sin City stories and then rearranging the scenes using his editor's instincts, he had the script completed in four days. Essentially, the comic books act as storyboards. Rodriguez then set about building virtual sets within his computer. Along the way, some small alterations were made to Miller's book of rules. Though still largely in black and white, the film utilises more frequent splashes of colour than the comics.

"Yes, some of that isn’t in the book," Rodriguez says. "The blood was the most interesting aspect of that. On the heroes, when it was just black-and-white blood, it looked like mud. You couldn’t feel the pain. As soon as I turned it red you feel oh, he really has been cut up. Before it didn’t seem like the hero had been making this big sacrifice. You turn it red and you feel the sacrifice. We ended up deciding that only the heroes’ blood would be red."

Sin City – thrilling, jarring, occasionally revolting – is easily Rodriguez' best picture to date. After enjoyable but never entirely satisfactory films such as Once Upon a Time in Mexico and Desperado, the young innovator has offered convincing evidence that his tidy, economic production strategy may be the way forward for low-to-mid-budget film-makers.

"Francis Ford Coppola saw my stages and said: ‘This was my dream for Zoetrope [the innovative quasi-studio he set up with George Lucas and others in the late 1960s].’ I really took that to heart. We are doing something that these experimental film-makers had been trying to do all those years ago."

And Rodriguez' methods are speedy. His next film, a kids' entertainment named The Adventures of Shark Boy and Lava Girl in 3-D, opens in the US in a few weeks.

"Oh, yeah, I have to get back to the garage and finish the trailers," he says guiltily. "But, you know, I have all the family working on it. So it’s fun. It’s like being involved with a family run restaurant."