The thing about casting a wide net is that you never know exactly what you'll catch - or, more to the point, how much.
When the filmmaker Kevin Macdonald met with the staff at YouTube to discuss asking people from around the world to submit footage from a single day in their lives, they estimated the website would receive around 10,000 clips. The idea was to make a movie by editing together the finest submissions.
"In the end, we got around 81,000 entries from 192 countries - which was more than 4,500 hours of footage. Vastly more than we expected," he says. "It was both a blessing and a curse. Could we logistically manage to catalogue and rate all that material?"
They did. For two months, a team of 23 translators spent up to 12 hours a day painstakingly sifting through the submissions. After more months of editing, Life in a Day premiered at the Sundance Film Festival in January and streamed simultaneously on YouTube for a brief period.
Produced by the filmmaking brothers Ridley and Tony Scott (Gladiator and Top Gun, respectively), the documentary shows fragments of the world on Saturday, July 24, 2010, from some 140 countries, including the UAE.
Some 350 people made the cut for the final film, which is set for release in the US and the UK this month, with international release dates to follow.
From a European parkour enthusiast leaping walls and riding on the back of a bus to African women singing while they pound grain to make bread, the film explores the mundane as well as the extraordinary. It also features a host of incredible characters; from a Korean man who has been cycling the world for nine years, to an elderly British couple who exchange hilarious vows on their wedding day and the members of a US family coping with a diagnosis of cancer.
Life in a Day manages to feel equally grand and intimate, while being both celebratory and tragic.
"Most of the world is represented in one way or another - that was extraordinary," says Macdonald, whose career began directing documentaries such as Touching the Void, but has in recent years moved into dramas, including The Last King of Scotland and State of Play.
The film features an extended clip telling the story of Ayamatti, an Indian gardener living in Dubai. From his modest single room, he talks about how he moved more than a thousand miles away from his family to find work and his gratitude for the life the city has granted him.
"A lot of the submissions were from people who were in positions of power in the world. He was someone who was not," says Macdonald. "He was a very lowly, presumably quite poorly paid migrant worker living away from his family, so he was the kind of voice that probably wasn't that well-represented in the film and is never heard in cinema."
But while Ayamatti might seem like an unusual candidate for film fame, the director says his hopeful outlook was incredibly common.
"Largely, what we found was that people were optimistic, even people going through terrible illnesses. Ayamatti was somebody who seemed to be at peace with himself and his lot in life - that attitude is what made him attractive."
It is also remarkable that a film that is essentially a collage of home videos succeeds at being so cinematic. As well as offering more breathtaking scenery, fascinating characters and raw emotions than the average 95-minute movie, the picture quality of the footage is almost entirely excellent. The filmmaking team's request that entrants use high-definition cameras, if possible, undoubtedly helped.
"You could only do this with modern technology, thanks to the internet and cheap, lightweight cameras that take good images," says Macdonald.
"Life in a Day could only have been made in the last few years, which, in itself, expresses something about the modern world."
The team chose a Saturday on which to stage the filmmaking experiment because, as part of the weekend in most countries, they believed people would have more free time in which to be more creative.
What the filmmakers had not anticipated was that July 24, 2010, was to have a full moon - something that inspired hundreds of the submissions. Also unexpected was the tragedy at the German music event, Love Parade, where a deadly crush inside a tunnel left 19 revellers dead. Footage from the confused crowd before, during and after the incident makes for difficult viewing.
"The whole process was one of opening your eyes to chance and fluke and serendipity. I tried not to go into it with too much preconception. I wanted to see what Lady Luck would provide and what the world was trying to say. Any day that you choose there would be something dramatic happening in the world, or other tragedies."
Although creating the pictures, sounds and stories that make up Life in a Day was outsourced to people around the world, the production team in London still had a sizeable task in editing the movie.
"Luckily, the world comes to London," says Macdonald. "We could find people who spoke pretty much every language in the world right here."
The 23 assistants, some of whom spoke several languages, rated the clips from one (the least suitable) to five (the most) and made rough translations of anything they found to be particularly interesting. Macdonald himself watched 250 hours of footage over two months.
"Obviously, you have to train those people, showing them what we liked and didn't like. But that meant we still relied in part on their taste in order to get the magic moments. I'm sure we missed a few, though."
In the hope of ensuring his assistants could identify these "magic moments", the director showed them a number of films that inspired him as a documentarian. These included Humphrey Jennings's 1942 picture Listen to Britain. Part of the Mass Observation movement in cinema, Jennings created a collage of the sights and sounds of the UK during the Second World War, with no voice-over or narration.
Also intended to inspire was the experimental 1982 documentary Koyaanisqatsi: Life Out of Balance, by the US filmmaker Godfrey Reggio. It consists primarily of time-lapse and slow-motion footage, set to the music of Philip Glass. Nikita Mikhalkov's movie Anna: 6-18, in which the Russian filmmaker asks his daughter the same three questions about life on each of her birthdays for 12 years, was also shown.
Life in a Day's method of production makes it one of the unique pictures in recent years, yet it is still unmistakably a piece of documentary filmmaking. Kevin Macdonald denies, however, that this represents a throwback to the films of his early career.
"This is a movie - it's something that I want people to see on the big screen. Like The Last King of Scotland, it has humour, tragedy, great visuals and questions about life and what it is to be alive, but it does it in a completely new way."
Follow us on Twitter and keep up to date with the latest in arts and lifestyle news at twitter.com/LifeNationalUAE