Steven Soderbergh has been a mainstay in Hollywood for the better part of three decades. His career includes a long list of critically acclaimed movies, one of which earned him a Best Directing Oscar in 2000. Soderbergh is known for experimenting with his films, and his latest is probably his most ambitious to date, shooting it using only a smartphone.

Soderbergh’s Unsane is described as “reality-type horror movie” similar to this year’s Get Out. It stars Claire Foy, Juno Temple and Jay Pharaoh. Soderbergh is self-releasing that project through his Fingerprint Releasing company, and thus has complete say in the film. One of his key experimentations he did with the movie was shooting the film secretly using an iPhone 7 Plus, according to Entertainment Weekly.

It is well known Apple makes some of the best smartphone cameras around, so it isn’t surprising a big-time Hollywood director decided to shoot a feature film using an iPhone. The iPhone 7 Plus has a dual 12MP camera with a wide angle and telephoto lens, with the wide angle lens being outfitted with optical image stabilization. Specifics about Soderbergh’s usage of the camera weren’t divulged, but we imagine he used stabilizing rigs and an added cinema lens to maximize the quality of the image he got from the iPhone 7 Plus.

Shooting Unsane using an iPhone gave Soderbergh the ability to edit the movie while on set. This enabled him to show cuts to the actors.

“So he’d be like, ‘Here’s a cut so far,'” revealed Jay Pharaoh of his experience with Soderbergh and shooting the movie using just an iPhone. “So I saw about 80 percent of the film. But I’m excited to see the whole thing, because it looks so dope — you wouldn’t be able to tell anything [about how it was made]. It looks that great.”

The entire movie was shot in just over a week.

Shooting films using an iPhone likely won’t become the norm in Hollywood any time soon. But it’s still interesting to see a very high profile director such as Steven Soderbergh be the first to experiment with the available tool. Unsane will be in theaters March 23, 2018.