LONDON (REUTERS) - British boy band One Direction, one of the pop music industry's biggest acts in the last two years, plan to show the world what they're really like in a new 3-D documentary which will premiere in London on Tuesday.

The five singers told a news conference in the British capital on Monday that This Is Us allowed them to present themselves in a more fulsome manner than they are depicted on videos, in concert and on the ubiquitous social media sites which track their every movement on and off stage.

"There is only so much you can get across in terms of your personality, you know, social media and like 10 minute interviews you do with people," singer Harry Styles said.

"So I think...(it's) a way for us to get across what we are like and what we are like with each other for the fans to see." Bandmembers Louis Tomlinson, Liam Payne, Niall Horan, Zayn Malik and Styles were all on hand to talk about the behind-the-scenes film and the media interest that has engulfed them since they first became a group on a British TV talent show in 2010.

The film, directed by Super Size Me documentary maker Morgan Spurlock, includes concert footage, life backstage and on the road. But Styles laughed off one reporter's question about whether footage of the band with groupies or drugs had been edited out.

"This is a family press conference," Styles said.

Spurlock said the film would show that part of the band's success stems from their down-to-earth personalities.

"Part of the reason I think they have been so successful with their fans is that they are so incredibly grounded and normal and that's what comes off in the movie, there's no air of superiority," he said.

Hundreds of fans have already started to camp out in London's Leicester Square for a chance to see One Direction walk the red carpet at the film's world premiere.

The band shot to fame on The X Factor television singing competition and have conquered the global market with two albums and a string of catchy hit singles. They said in May they are working on a third "edgy" album and will embark on a world tour next year.

One Direction, whose members are aged in their late teens and early 20s, topped the Billboard 200 album chart twice last year with Up All Night" and their second album Take Me Home.

They were named Billboard's top new artist/group in 2012.