If you thought the Imax 3D experience was out of this world, try watching it from the projectioner's window... I felt literally in at the deep end when I joined the National Media Museum's senior projectionist Tony Cutts at work.

As the opening credits to Deep Sea 3D rolled and a giant wave rushed out of the screen, followed by a huge shark darting towards me in terrifying three-dimensional glory, I leapt backwards with a yelp.

The projection room overlooks the massive Imax screen - 64ft across by 55ft high - and when Tony starts the film, images come pounding through the window. As a succession of eerie deep sea creatures such as fried egg jellyfish', angry-looking eels, rainbow-coloured turtles and a giant octopus float by, it's like being in a submarine.

Tony has seen it countless times and doesn't flinch. "I love seeing children reaching out to touch' 3D images," he smiles. "There's nothing to rival Imax 3D in terms of clarity and impact."

Tony has been a cinema projectionist for 52 years and has been at the museum since 1992. He works in the Imax, Pictureville and Cubby Brocolli cinemas and gives talks to film festivals and museum visitors.

The first thing I see are huge reels of film stacked up on plates'. "Imax uses 70mm film, whereas normal film is 35mm," says Tony. "Normal film runs through the projector vertically but on Imax it runs horizontally because the frames are so big. The rolling loop' movement, advancing the film in a smooth motion, is key to the impact of Imax."

The reels are too heavy to lift manually so they're transported on a forklift.

"Feature films are rented to us but we buy Imax films. 3D films cost £30,000 each," says Tony.

When I arrive he's preparing the first screening of the day - Deep Sea 3D. "It takes an hour to get everything up and running. Every morning I clean the projectors, removing any particles from the film, and vacuum the floor. Because of the ventilation it's practically a dust-free atmosphere in here and there's 50 per cent humidity so the film doesn't buckle."

A new film arrives in sections of three to five minute lengths which have to be joined together. This takes two days. "The Harry Potter film came in 42 parts!" says Tony. As he talks, he links strips of film from the reel to two huge projectors. A group of schoolchildren are watching, awestruck, through a film gallery window allowing visitors to see the projectionists at work.

When 3D Imax was introduced, the old projector - now on display in the museum - was replaced with two new ones, designed for three-dimensional film.

"Nearly every Imax film is 3D now," says Tony. "With 3D you need two projectors because there are two films running; one projector sees what the left eye sees and other sees what the right eye sees. One screen is polarised vertically and the other horizontally, like glasses."

With thick wires like tentacles spilling out of them, the projectors look like Dr Who creatures.

They are the world's most advanced, precise and powerful projectors, containing 7,000 watts of light. During projection the film is sucked against the back of the lens by a vacuum for a 24th of a second. Any dust on it will look like a football on the big screen so it goes through a cleaning process on the projector, running through particle-remover rollers taking the dust off. "The Imax experience should be flawless so when the film is running I keep an eye on the screen to ensure no specks show up," says Tony.

The sound comes on DVD discs loaded onto a computer. "We have to make sure the film is in the right place before it starts rolling, or it'd be out of sync and we'd have to start it again - thankfully that hardly ever happens!"

As Tony laces the film around the two projectors it's odd to see little Imax scenes stretched around the room. I try not to walk into film strips and bring the whole thing crashing down!

Peering out of the window, I see the auditorium filling up. Tony switches on the projectors and the noise is like an aeroplane setting off. They move together on tracks to the central position for projecting the film.

The lights go off and a booming voice announces: "Ladies and gentlemen, you're about to experience Imax."

Sound quality is essential to Imax. Tony shows me the wall of speakers sending crystal-clear sound around the auditorium. There are seven sound channels using 12,000 watts of power.

Suddenly there's a T-Rex charging out of the Imax screen - a trailer for a new film coming soon - then Tony's window is filled with deep blue sea and weird and wonderful creatures floating by.

How lucky we are to have an Imax screen on our doorsteps.

There are eight daily Imax screenings and Tony has 15 minutes between 2D films and 20 minutes between 3D films to change the reels and re-set the projectors. "It used to take ten minutes to rewind a film so we needed more turnaround time, but we don't rewind now," he says, showing how he twists the centre of a reel around his fingers ready for it to go again. "Film used to arrive on spools of 20 minutes so we were constantly changing them during the film, hoping that nobody would spot the join."

Tony has always been passionate about film. "At school we had a 16mm projector and one day the teacher put a projector lid on my desk. He didn't know how to lace it up so I looked at the diagram on the lid and worked out how to do it. After that I was always called out of lessons to set it up.

"When I told the careers officer I wanted to be a projectionist he said What's that?'. He sent me to the Morley Street picture house, now the Alhambra Studio, and the manager tried to talk me out of it. He said Cinema is dying, television is the future'."

Aged 15, Tony started working at Morley Street until it closed in 1957. He moved to the Gaumont - where he met the Beatles - and later moved to the Majestic in Leeds - where he showed The Sound of Music for more than two years - returning to the Gaumont two weeks before it opened as the Odeon.

The first Imax film he ever saw was To Fly. "I felt dizzy afterwards," he recalls. When he started working at the museum he had two weeks to learn about Imax.

Tony clearly loves his job. "There's something satisfying about preparing a film and showing it to a full house. There's only one projectionist at multiplexes; they just set a timer, so you don't get the same kind of presentation."

A highlight of Tony's year is Bradford Film Festival's Widescreen Weekend, when old films are given an airing on the Imax. "Film buffs, projectionists and cinema managers come from around the world - it's a wonderful atmosphere."