Coming soon: 3D film reaches new heights as latest technology brings Sir Edmund and Tenzing Norgay's historic 1953 Everest ascent to life

New footage will be merged with film and photographs of the 1953 expedition taken by George Lowe

As extreme film shoots go, Beyond the Edge takes the Kendal mint cake. A crew is hanging off the Lhotse Face of the world's highest mountain, filming a 3D thriller re-creating Sir Edmund Hillary and Tenzing Norgay's 1953 ascent of Mount Everest.

The 3D team, which shot Avatar, is on location on Everest for eight weeks, until June. The crew has had to deal with extremes of cold, frozen cameras, weather "changing on a dime" and the harsh light that comes with shooting at high altitude.

The new footage will be merged with film and photographs of the 1953 expedition taken by George Lowe. That old footage will be cleaned up and retro-fitted into 3D so the films merge "seamlessly" using the same technique used by James Cameron to convert his film Titanic.

The Everest shoot "has not been easy, to say the least", said producer Matthew Metcalfe, speaking in the more agreeable surroundings of the Cannes Film Festival. The crew has a helicopter on permanent stand-by. "The weather changes so fast you think that it looks fine, but people in the know say: 'We've got 15 minutes to get out of here,'" he said. "Before you know it, a massive front will come in."

Beyond the Edge will chronicle Hillary and Tenzing Norgay's dramatic scaling of the mountain in 1953 and the extreme conditions that they faced with rudimentary equipment. When Hillary descended he told Lowe: "Well, George, we knocked the bastard off."

The crew has already shot six weeks' worth of footage in New Zealand's Southern Alps, which many climbers use as a training ground. Hillary climbed his first mountain in the range aged 20.

Mr Metcalfe decided against a traditional drama "because I feared it would force us to take liberties with the story", and will opt for documentary footage with narration from figures including Hillary himself. The film-makers have cleaned up hundreds of interviews.

Mr Metcalfe said: "There is something about the purity of these adventure stories. There's something about these guys and the feeling they were the 'real deal'. They didn't do it for money or fame. They did it because it was there. They did these things simply because they wanted to improve themselves and improve what humans could do."