A movie made on an iPhone for just $12,000 will screen at the New Zealand International Film Festival next month.

Police senior constable, novelist and filmmaker Stefen Harris made his third feature film, Blue Moon, in just 30 hours at a Motueka petrol station with lead actors Mark Hadlow and Jed Brophy.

The thriller unfolds over one night, with old school friends Horace Jones (Hadlow) and Darren Cates (Brophy) facing off in an all-night petrol station early one morning.

Supplied The film Blue Moon was shot on an iPhone in a petrol station in Motueka over just 30 hours.

Harris said he wanted to make a film quickly and cheaply after years trying to raise $1 million for different feature film ideas. His first movie, The Waimate Conspiracy, was released in 2006, while his second, No Petrol, No Diesel!, came out in 2009.

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"You can get sidetracked chasing a million dollars year after year, project after project. So I just went back to my roots. It was either make a film on a budget or not make a film at all."

Hadlow suggested they shoot on an iPhone after seeing the success of 2015 film Tangerine, which was made on the cell phone and was critically lauded at festivals around the world.

They fitted the iPhone with a special wide lens and used a gimbal stabiliser to keep the camera steady.

"We had a lot of offers of different high-spec cameras, but I knew we would end up fiddling about with the camera and losing time," Harris said.

"We wanted the speed of the iPhone."

They could only shoot in the petrol station when it was closed between midnight and 5am. They filmed over six nights, giving them just 30 hours to wrap the whole film.

"We didn't have time to kick back or rehearse anything very much at all."

"It was a very intense and fast shoot. We were going flat out. There wasn't time to draw breath between takes."

The film was funded with $10,00 from the Tasman District Council, $1000 from the Police Credit Union, which grants scholarships to police staff, and $800 raised from a charity screening of his first film.

The cast and crew all worked on deferred fees, meaning they will only get paid if the film makes money. The New Zealand Film Commission granted $25,000 for editing and sound mixing once the shoot had wrapped.

The whole film was made in Harris's spare time when he wasn't working as a police offic in Motueka.

"I can't help it really. I have written stories all my life. You can't choose not to do it. Stories just turn up and you have to write them down."

The film will screen in Christchurch on August 8, 11 and 15 as part of the New Zealand International Film Festival.