Filmmaker Sean Baker (Four Letter Words, Take Out, Prince of Broadway, Starlet) premiered his new film Tangerine at the Library theater Friday at the 2015 Sundance Film Festival. A Q&A followed the screening during which Baker revealed that the film was shot entirely using three iPhone 5S phones. (Update: Our original story said “almost entirely,” before the film’s team provided a correction.) The revelation got an audible gasp from the crowd who had just watched the movie. It’s not the that film looked amazing — it had a digital look to it for sure — it’s just that no one could tell that it was shot on iPhones.

During the question and answer session at the sold out Library theater screening, Bake held up his iPhone and proclaimed that it was one of the three iPhones used to shoot the movie (He joked he’d stolen the phone from the production).

Tangerine is a dramedy about a transgendered hooker “who tears through Tinseltown on Christmas Eve searching for the pimp who broke her heart.” Not a hugely accessible subject matter, which is why the film was funded on such a low budget. The film also features mostly newcomers — Baker found his two transgender leads, neither of whom had prior acting experience, at the LGBTQ center in Los Angeles.

But couldn’t they afford to rent a Canon SLR or something better? Were iPhones used as a gimmick? It seems like the iPhones were chosen not just as a cost cutting measure but also to allow them to shoot in public places (such as the LA Metro subway and bus line) without permits or permissions. It was revealed that the LA city bus driver called the cops on them because a filmed argument looked “too real” during a scene which took place on the bus line.

And how does the footage look better than you might expect from a consumer smart phone? Baker used a couple things to “elevate the look,” including a set of Moondog Labs anamorphic lenses, which could be attached to the phone, and also an app called Filmic Pro which was used to get the film’s grainy look. The latter allowed more control over the captured image than Apple’s camera app. He also mentioned they used a steadi-cam type device with the phone to achieve some shots.