ON the website that accompanies Mark Cousins's latest film there's a claim the movie cost a mere £10 to make.

This is, in fact, a shocking inaccuracy. The real cost, he tells me as we sit in his Edinburgh home, was more like £5.80. He bounds up and burrows around on his desk to find a photograph of the revolutionary Soviet film director Sergei Eisenstein. This is what he blew the budget of What Is This Film Called Love on: laminating this photo so he could carry it around the street of Mexico City for three days while talking to Sergei.

As you may have already gathered, The Dark Knight Rises, it is not. What it is, is a film essay, inspired by Virginia Woolf and the great documentary-maker Chris Maker, about travelling and the end of youth. It is also the most naked portrayal of Cousins we've seen so far (and I'm not just talking about the bit where he is walking around in Death Valley wearing nothing more than a smile).

Made with a £100 camera that was given to him by his partner Gill, the film attempts to capture what it's like to be alone, he says. "I love solitude," Cousins says, "that lovely phrase in Japanese, mano no aware – the sadness of time passing."

But trying to capture that, he says, was the scary thing about the movie. "The naked bit doesn't bother me at all. I'm totally cool with that. But asking an audience to sit with you for 76 minutes while you say: 'Here's what I thought ... '"

Cousins has been a familiar face and voice to anyone who loves cinema over the last couple of decades, whether as a writer or as the director of the Edinburgh Film Festival, as presenter of the Scene By Scene TV series or, way back in the early 1990s, Moviedrome. And that's without mentioning his 15-hour magnum opus The Story Of Film.

I've known him a little longer. We were on the same film and media course at Stirling University back in the early 1980s (he was in the year below me). His love of cinema was pretty clear back then. He's spent the best part of a quarter-century since evangelising for that love.

He's 47 now. There's a line in the film where he says that leaving youth is hard. "Don't you think?" he asks when I bring it up. "I feel that I'm at the moment where I can no longer pretend to be youthful. I don't think I've been pretending exactly but it's now definitely gone." Was it a difficult thing to say goodbye to? "Yeah, the vitality of that. The feeling of being alive. It's not only getting older. It's losing friends. We've had a lot of friends die of cancer. It means there are grey clouds in the sky. The sky for me is still blue, but there are big grey clouds there and they don't go away and they cast their shadows and I presume they accrue as we get older."

He worries about his knees because he would hate not to be able to walk and he worries about losing his eyesight. "Some people's greatest pleasure is through their sex organ or through their brain. Mine is through my eyes and I'm terrified of losing my eyesight." But these are neuroses rather than real fears and, if anything, he thinks he is speeding up rather than slowing down.

That might be, he thinks, because he's begun to shake off the timidity that came from his Northern Irish upbringing. "I feel I was very defined by my working-class Belfast background. You couldn't consider calling yourself a creative person. And now I don't give a f*** about that. I can be whatever I want because there's only one chance. I'm much looser and freer about that."

Childhood was Charlie Pride and Elvis and the background noise of the Troubles. He was the (twin) son of a mixed marriage. "They had to keep it a secret and once word was out you had to move on." From Belfast they went to Ardglass and then to Antrim. He went to school in Ballymena, "a little Catholic enclave". "I remember during one of the unionist strikes the farmers got their tractors and closed off Ballymena and we had to stay in school overnight in case 'those bad people' got us."

Perhaps then the nervy boy he was is understandable. But he was smart too. Good at science and the arts. When we speak he has just watched a documentary about the Undertones. "Gill was saying 'I love the Undertones' and I said 'well, I was much more iffy about them because of My Perfect Cousin and Jimmy Jimmy. Those two songs were about having a brainy, nerdy, weedy, poncey relative. And I was brainy, nerdy, weedy and poncey, so how could I possibly buy into the Undertones?"

Coming to Scotland and university was a revelation for him. He tasted alcohol for the first time, met Gill (they've been together since 1984), and developed his childhood love for cinema into a passion. "Sometimes you desire something and then when you get to know it, it disappoints. It isn't as complex and rich. But movies are. You open the door on cinema and it looks like a little door and you discover a huge mansion and it's got so many rooms. I used to have a nightmare that I'd run out of movies to see and now you just realise there's so much and it's so rich."

What I've always liked about him is this enthusiasm. While other, older, critics are suggesting we have reached the end of cinema, he believes it's still young.

"These people who talk about the endgame of cinema are just entirely wrong and being nostalgic, which is very self-defeating. I saw this phrase the other day: yesterbation. Isn't that a good word? They're yesterbaters, these people."

Still, it's clear the media no longer shares his cinephilia. In many ways that was what happened with Scene By Scene. He wanted to embrace world cinema; the BBC, who made it, he feels, "wanted to go more in the showbizzy direction ... I guess."

That said, he thinks he was never very good on TV. "TV is too cool a medium for an edgy, nervy person like me." He'd watch himself and think 'would you just sit still?' He also struggled about becoming a public figure. "I didn't read reviews but I know there was a lot of negative stuff said about me. When I was first on I read something in The Times and it commented on how skinny I was. And it was like being back in the schoolyard being bullied again. When you'd been bullied those memories are so indelible so I just thought, 'No, I'm not going to read that.' Drunk people would come up to me and either criticise me or try to snog me and you never quite knew which."

Appearing in his new film is much easier, he says. He feels much less exposed even when he's, ahem, fully exposed. "There's this phrase that Calvin has that the body is the prisonhouse of the soul, that the body is a container and that just doesn't feel true to me. Bodies don't feel like containers at all to me. They feel like surfaces. That's why I say in the film when I'm naked I feel more like a camera. I'm absorbing more stuff. In most religions you're taught that the body is a shameful thing and it's the utter shame of the nation in which we're sitting in that Steve Gough, the Naked Rambler, is still incarcerated."

Cousins sees his future as, well, "making art, I guess". He's hoping to make a film about Belfast and he's started a film about architecture and memory with his little £100 camera. "I live really cheaply. I don't take taxis. I don't go to fancy restaurants, so I can make these little independent films."

In a way you could argue that his is a superhero story like Batman after all. A story about a brainy, nerdy, weedy, poncey boy who transforms himself not by radiation or alien powers but by truly embracing his brainy, nerdy, weedy ponciness and showing us how great those things can be. "I'm still very much the little boy that sits in front of the screen agog."

In his latest film Cousins talks of Eisenstein's quest for five ecstasies. Before I leave I ask him for five of his. "Cinema. Coming home after a long flight in row 47, seat B, having a bath and making pasta sauce. Jumping into Eas Fors waterfall in West Mull, one of the greatest things I've done. Playing music full blast, getting drunk and dancing naked ..." He pauses, thinks. "Can it be a hypothetical? Knowing that nobody around you is going to die for a while."

That's beyond all of us, alas. Whatever the budget.

What Is This Film Called Love? directed by Mark Cousins is shown at the Macrobert, Stirling, at 7pm on October 6.

Mark Cousins

film director