Keanu Reeves - Lots of excellent new adventures

Like the subject of his new documentary, Side by Side, Keanu Reeves seems to be at a tipping point, a transitional stage in a 28-year career that has seen him navigate between huge blockbusters (Speed, The Matrix) and more idiosyncratic projects. He may not admit it, but despite looking youthful for his 47 years, he must secretly know that playing the leading man – as he will do later in the year, in the 18th century-set samurai tale 47 Ronin – has a shelf life.

So it's no surprise he's gone behind the camera for the first time, producing Side by Side, a film he originated with its director Chris Kenneally. Moreover, it's no vanity project, but an insightful snapshot of his industry at a crucial crossroads in its history. Examining the history and process of both digital and photochemical film, Side By Side weighs up the merits of both at a time when digital cameras look set to make the more traditional methods of shooting on actual film stock obsolete.

Reeves has flown in to Berlin, to present Side by Side at a film festival he seems to like (he accompanied both Thumbsucker and The Private Lives of Pippa Lee here). We meet in the Glashütte Lounge, on the 21st floor of a building in the Potsdamer Platz, offering a stunning panoramic of the city. It's shortly before 1pm, and Reeves is already reaching media saturation point. "OK, one more before lunch," he tells the PR, before she ushers me across to the cordoned off area where he's sitting on an uncomfortable-looking designer sofa.

My past encounters with Reeves have found him an awkward interviewee, vaguely suspicious, unwilling to articulate anything but the barest of information. But today, he's pumped with enthusiasm for what is clearly a passion project. Dressed in a charcoal suit, waistcoat, pale shirt and a pair of beige walking boots, presumably chosen to combat the snow outside, he even finds time to raise a smile when I ask if he's found any time to visit Berlin's world famous clubs. "Clubbing? I'm too old for that."

Side by Side began when Reeves was working on the 2010 low-key thriller Henry's Crime, in which he starred. "This experience was really based upon interest," he explains. "The cinematographer Paul Cameron was showing me these images on this 5D digital camera, and we were looking at the digital image and the photo-chemical image side by side and I was like, 'Film is going away? Woah! What's happening? Is this the end of film? What is going on here?'"

It was at that point that Reeves partnered up with Kenneally, who was working as post-production supervisor on Henry's Crime, and decided to document this transitional moment in film. "From the very beginning, Keanu had a strong curiosity to know how everything worked, while we were in post," Kenneally later tells me. "How does the lab work? Where does the film go next? And then how does it go to digital? He really dissected it all and wanted to know the process. I've seen him do that with the camera too – he breaks things down. He's just interested in things and how they work."

If the film carefully sidesteps the highly subjective question of which format is better, the roll call of interviewees is illustrious. Directors such as Martin Scorsese, David Lynch, Steven Soderbergh, Christopher Nolan, Lars von Trier, Robert Rodriguez, David Fincher and James Cameron all make appearances, alongside equally distinguished cinematographers such as Michael Ballhaus (GoodFellas), Vittorio Storaro (Apocalypse Now) and Anthony Dod Mantle (Slumdog Millionaire).

It doesn't stop there, with lesser-known below-the-line talents given equal billing. "As I started learning more about the subject," notes Reeves, "it would be like, 'Well, why aren't we talking to them?' So we'd go, 'Let's go and see if we can meet them!'" Most are not former collaborators, though Reeves does call upon the creators of The Matrix – the Wachowski siblings – to discuss what became a groundbreaking moment in film-making.

So does he view The Matrix, with its revolutionary digital effects, with different eyes now? "I think you have to because time has gone by," he replies. He cites the influential "bullet time" sequences, where the camera appears to rotate around a slowed-down image. "The deeper thing that happened was it was computer generated. It was a digital moment. And that can only be put in the context by the passage of time, generally speaking. John Gaeta, who did the visual effects, knew what was going on, and so did the Wachowskis – but I didn't."

While it's not addressed directly in the film, we move on to the subject of actors being replaced by digital avatars in the future. "I think technologically that would be possible, but I think it would depend on the film-maker, in terms of whether they want reality or not," says Reeves. He admits he's concerned about the possibility of manipulating an actor's performance digitally – "like putting tears in your eyes when you don't want tears". Though if you were being cruel, some of Reeves' more wooden performances probably would benefit from some digital tinkering.

With Reeves proving an adept on-camera interviewer, he admits most of those asked to participate were enthusiastic because it was a subject close to their hearts. "When we walked into a room, it was never like, 'Who are you? Why am I here?'" It's easy to imagine that for someone who has been in the business as long as he has, meeting film folk would be par for the course. But you sense something of the fanboy in Reeves. "Sometimes, I'd be like, 'You know we've just interviewed George Lucas. He's just hung out with us and told us the deal. The real deal.'"

Reeves, of course, has enjoyed his time with a few great film-makers but did meeting all these other cinematic legends whet his appetite to work with them? "Yeah! Yeah! Mmm," he says, savouring the thought. "I'm a fan of their films, and to meet them as people... you feel like you'd be able to special work with them. A different kind." Did it reinvigorate his desire to act? "I wouldn't say that. I've never had that moment where I felt 'I don't want to do this anymore.'"

Even so, Reeves does admit to a midlife crisis that he suffered a while back. "I had the classic 40 meltdown. I did. It's embarrassing. It was pretty funny. But then I recovered. To me, it was like a second adolescence. Hormonally, my body was changing, my mind was changing, and so my relationship to myself and the world around me came to this assault of finiteness. It was also the end of the projection of my younger self. I came to the place where I thought, 'I don't know where I am anymore but where have I come from and what am I doing?'"

The way he talks, you might think the Canadian-raised Reeves is as mournful-looking as the photo that did the rounds on the internet in 2010 – a paparazzo shot, dubbed "Sad Keanu", of him eating his lunch on a park bench.

Rather than sad, he comes across as more introspective and thoughtful than he's often given credit for. After scratching his creative itch, producing and presenting Side by Side, he is now planning to direct his first feature Man of Tai Chi – an ambitious-sounding English-Chinese co-production, which he plans to shoot in Mandarin and English. Co-starring Reeves and Tiger Chen, who was one of the stunt team on The Matrix, it's a martial arts story, pure and simple – with Reeves promising 18 fights. "It's about 40 minutes of fighting," he says. "I want to make a good, solid kung fu movie."

Man of Tai Chi sounds like a tantalising prospect, and an ideal companion to the forthcoming 47 Ronin. A $170 million blockbuster, it's a reworking of a classic Japanese legend, in which Reeves plays an outcast who joins a band of samurai seeking revenge for the death of their master. "Japanese kids grow up with this story told to them," he says. "They hear it from family and they learn it in school. It's part of the culture. It's been made into movies many times and on television. It's like our Westerns, the story keeps being told."

Noting the new version has been reworked "with great care and respect", if fans are starting to worry that this new, mature Reeves is going all reverential on us, fear not. I ask him about the long-rumoured third outing for Bill S Preston and Ted Theodore Logan – the time-travelling, guitar-rockin' duo that earned Reeves cult status when he starred in 1989's Bill & Ted's Excellent Adventure? "Yeah, we have a script," he confirms. "We're trying to put it together. It's a good script too." Excellent, as they might say.

'Side by Side' and '47 Ronin' will open later in the year