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A landmark film showing a snapshot of Kiwi life in 1970 has been digitally remastered and converted for use on regular cinema projectors.

This Is New Zealand is a 20-minute cinematic journey through the country that took a year to shoot in 1969. It was shown to 2 million visitors during the Expo 70 showcase held in Osaka, Japan.

The film was shot by long-serving National Film Unit director Hugh Macdonald. It was moth-balled for decades in the film vault of first the film unit, then Archives New Zealand because of the complicated three projector set-up required to show it.

Inspired by A Place to Stand - a Canadian tourism film shot by film-maker Christopher Chapman that had up to 15 separate moving images on the screen at once - Macdonald decided on a similar, if simpler approach.

"We looked at [the Canadian film] and thought, this is too cluttered," he said.

Three cameras were used to simultaneously shoot scenes for the film, to create sweeping aerial panoramas of the Southern Alps and also to place contrasting images side by side.

"Like a lot of film makers, we wanted to make something we'd enjoy ourselves," said Macdonald.

"It has a very abrupt ending. We only had 2000 feet (600m) of film."

The film itself features scenes from everyday life in 1969 - a cricket game at the Basin Reserve, a kiwi foraging through the undergrowth, children playing in a schoolyard. Dated snapshots from tourism adverts of the time feature the slightly Orwellian catchphrase: "New Zealand is yours. Go there now."

The film highlights the extent of New Zealand's diversification in the intervening 37 years.

Although it was shown in main centres to about a quarter of the population in the early Seventies, Macdonald said the tonnes of equipment needed to run the three-projector system and separate sound unit prevented it from being shown to more people. Former Act Party president and TV journalist Catherine Judd was involved in the filming.

Park Road Post, the post-production facility formed when Peter Jackson bought the remnants of the National Film Unit in 1998, scanned the three separate 20 minute films, digitised them, colour-corrected them and removed blemishes, then made a high-definition digital version and also transferred them to fresh film. Most significantly, the process merged the three reels of film together, creating one film that can be played on regular projectors.

Previous attempts to create a combined film image resulted in a drop in quality. The film was also remixed in Dolby 5.1 surround sound.

Park Road Post colourist and telecine manager Jon Newell said most of the alterations to the film were cosmetic, a testament to the quality of Macdonald's original film-making.

Archives New Zealand is storing a digital version of This Is New Zealand across three hard drives - 1.25 terabytes of storage.

The head of the archive's audio visual records division, David Smith, said he was looking at digitising more of the 21,000 reels of film stored in the archives, but that widespread conversion to digital was too expensive.

"The ironic thing is, it's more cost effective to preserve film on film. It guarantees it for 100 years or more. With digital you have to store it on hard drives and migrate it as formats become obsolete," he said.