As Christopher Nolan's cinematographer, Wally Pfister has been widely acclaimed for the Dark Knight trilogy, Inception, Memento, Insomnia and The Prestige.

With one Oscar and three other nominations in less than a decade, he was at the peak of his trade in Hollywood. When he wasn't working with Nolan, Pfister was shooting such prestigious movies as The Italian Job, Moneyball and the Bob Marley documentary, Marley.

But directing his own movie was a completely different experience. Unlike most directors, who take on a modest film to learn the ropes first time around, Pfister jumped straight into a $US100 million Hollywood blockbuster starring Johnny Depp. Throw in a likely $US50 million to release the movie around the world and precious few debutants have ever had more at stake.

''I know,'' says Pfister with a laugh. ''What was I thinking?''

The New York filmmaker, who is heading to Byron Bay with his Australian wife next month, has the sci-fi thriller Transcendence heading for cinemas. Depp plays a scientist researching artificial intelligence who uploads his brain to a supercomputer, leaving his scientist wife (Rebecca Hall) and best friend (Paul Bettany) to deal with the consequences.

Like Inception, it is a movie brimming with ideas: that humans can achieve ''singularity'' and create a machine that thinks like a human, that the internet is a threat to our freedom as well as a blessing, that there will come a time when we regret technological advances.

Set in the near future, Transcendence has anti-technology extremists fighting to stop AI being developed. ''Most of the scientists and professors think that singularity is right at hand,'' says Pfister. ''It's maybe 20 or 30 years away. So [the subject] opens up all kinds of questions about the ethical use of machines and artificial intelligence.''

While Nolan was executive producer on the film, Pfister was on his own when it came to directing. ''I approached it in the same way systematically that I did the films of larger scale that I did as cinematographer,'' he says. ''That is, you take one little bit at a time and you keep picking away at it until you get to the point where you feel comfortable.

''So, while it might have been intimidating to me to be a first-time director, obviously I've spent 25 years on film sets, so the mechanics of it weren't as daunting as they might have been.''

What did he learn from Nolan, who has become one of Hollywood's leading directors in the past decade? ''One of the great things you observe is what a true gentleman he is,'' Pfister says. ''He's always treated his cast and crew with an enormous amount of respect. That's something I've always looked up to Chris for and I think that's a great model for how a director is supposed to be.

''And from thereon in, you've got to figure it out for yourself. Somebody can't ride the bicycle for you.

''As a first-time filmmaker, no matter what, it's going to be on-the-job training.''

Pfister's interest in film started with a movie shot in his neighbourhood when he was a boy in the early 1970s. ''One day, these trucks were rolling up the street that I lived on,'' he says. ''We went up the street and watched them filming a movie called Shamus with Burt Reynolds and Dyan Cannon.

''I was really fascinated by the process of filmmaking. I began to watch more and more films as a young man and really felt at a very young age that this was a career that I wanted to pursue.''

He had an unusual career path for a Hollywood cinematographer - shooting news and documentaries in Washington until Robert Altman came to town to shoot the HBO mini-series Tanner '88. After joining Altman's crew, he moved on to horror films for Roger Corman.

Pfister's partnership with Nolan began after they met at the Sundance Film Festival in 1998 and, not long afterwards, worked together on the ingenious Guy Pearce time-shifting thriller, Memento. But all along, even as the movies grew bigger, more spectacular and more successful, Pfister wanted to be a director.

''If you're appreciating films in general, you're appreciating more than just fine photography,'' he says. ''For me, the longing to be a storyteller and to at least try it existed for a long time. It managed to manifest itself as I got a little bit older and realised it was something I really needed to do before too much time passed.''

When his agent drew his attention to new writer Jack Paglen's script for Transcendence, Pfister became fascinated by its originality, topicality and the love story at its heart. It reflected his own love-hate relationship with technology.

''I keep a very open but sceptical mind about what AI will bring to the forefront,'' he says. ''We've become somewhat enslaved by our mobile phones, our tablets and our laptop computers and at the same time we can't live without them.

''So it's important for us to be very careful about how much information is being extracted from us by these devices as opposed to what we're actually gaining from them.''

Ironically for a movie about technology, Pfister defied the trend to digital filmmaking by having his cinematographer, Jess Hall, shoot Transcendence on 35mm film. He insists it is still the best format for a movie that will be shown in cinemas.

''I feel an obligation to an audience, if they're paying full boat to see a movie on a big screen in a multiplex, to present it in the best image quality,'' he says. ''And I know a lot of other filmmakers feel the same way and are still shooting on film.

''J.J. Abrams chose to shoot the latest Star Wars movie on film. Christopher Nolan still shoots on film and IMAX. Paul Thomas Anderson shoots on 65mm film.

''And even independent filmmakers, like Jeff Nichols and Wes Anderson, shoot on film as well.''

Once Transcendence opens, Pfister will head to Australia with his wife, Anna Julien, who grew up in Sydney.

''We're going to have a holiday in Byron Bay in May to see all our rellies there.''

In the meantime, he is thankful to have had such a strong cast for his first movie. ''It's like being a mediocre guitar player in a band,'' Pfister says. ''You hire a great bass player and a great drummer and you sound a lot better.''

Transcendence opens on Thursday.

Direct approach

 How many cinematographers become successful directors? Surprisingly few, it turns out. If Wally Pfister needs inspiration for his own career change, the best example is George Stevens, who went from shooting Laurel and Hardy comedies to directing such classic films as Woman of the Year, Gunga Din, Giant and Shane.

Nicholas Roeg was cinematographer on Lawrence of Arabia, Fahrenheit 451 and Far from the Madding Crowd before directing Performance, Walkabout and Don't Look Now.

More recently, Barry Sonnenfeld shot Blood Simple, Big and When Harry Met Sally before directing The Addams Family Values, Get Shorty and the Men in Black movies.

Jan de Bont shot Die Hard, The Hunt for Red October and Basic Instinct before directing Speed, Twister and Lara Croft Tomb Raider.

Many notable cinematographers have had a go at directing, including Australia's John Seale with the ill-fated 1991 adventure-romance Till There Was You.

But it says something about the importance of the script and performances that many more writers and actors have made successful moves to directing.

GM