The American director, who had only a few years ago declared his retirement from filmmaking, told reporters that “Unsane”, his first time using a smartphone for a full feature, had been invigorating.
“This is a really fascinating time to be making films,” he said, noting that “Unsane” had been shot in just two weeks.
“The gap now between the idea and the execution of the idea is shrinking. I wish I had had this equipment when I was 15.”
“Unsane” stars British actress Claire Foy of the Netflix series “The Crown”, who swaps her cut-glass accent as a young Queen Elizabeth II for the drawl of Sawyer Valentini, a Pennsylvania office worker.
Sawyer has left her hometown under mysterious circumstances and, feeling lonely, turns to online dating to meet men.
After an ambiguous encounter that leaves her upset, she seeks help from a counsellor at a local clinic, who tells her to sign a routine form before she leaves.
Within minutes, she is committed to a mental institution against her will and pumped full of pills.
A fellow patient, who says he is an investigative journalist, tells her she's been locked away as part of a massive insurance scam but that if she keeps her head down, she will be released within days.
However when Sawyer encounters an orderly she claims has been stalking her for two years, the audience begins to question her sanity as well — giving the film its ambiguous title.
'Inches from their faces'
Occasionally grainy iPhone sequences resemble surveillance camera footage, enhancing the Hitchcockian sense that Sawyer is being watched.
Soderbergh, 55, who also serves as his own cinematographer under the pseudonym Peter Andrews, said working with the smartphone had created an unprecedented speed and immediacy for him on set.
“I had the lens closer to the actors in this movie than I ever had a lens close to an actor before,” he said, after a well-received press screening.
“There were moments where it was inches from their faces. I felt it was necessary and appropriate for a movie that had to feel very visceral.”
Soderbergh said that for audiences, seeing phone images on a big screen should create an eerie sense of deja vu.
“We're so familiar with the aesthetic of phone imagery that I think without even knowing it, there's an intimacy between the viewer and the screen,” he said.
“There's a quality to those images that you're surrounded by in your life.”
The plot resonates in the #MeToo moment, with various characters appearing to try to “gaslight” Sawyer by telling her that her ordeal is all in her head.
“Unfortunately these are issues that have been around forever,” Soderbergh said, adding that the “topicality” had been “pure coincidence”.
“But I'm certainly interested in these kinds of dynamics, not just gender driven dynamics but power dynamics,” he said.
'Tricky to go back'
Soderbergh said that despite a few technical hiccups like a greater sensitivity to vibration, iPhones were likely to remain in his filmmaking toolbox.
“It's going to be tricky to go back to a more conventional way of shooting,” he said.
“Unsane” is not the first feature film made on a smartphone.
US director Sean Baker, whose current movie “The Florida Project” is nominated for an Academy Award, made his name in 2015 with “Tangerine”, which was shot on iPhones due to his shoestring budget.
And France's Michel Gondry (“Eternal Sunshine of the Spotless Mind”) made the short film “Detour” last year on iPhones for Apple.
Soderbergh, best known for the “Ocean's” heist movies, “Erin Brockovich” and “Sex, Lies and Videotape”, is an avid innovator who likes to play with genres and formats.
His recent HBO series “Mosaic” with Sharon Stone was released last month on television and as an interactive mobile app, allowing the viewer to choose the perspective from which to watch.
Further features let audiences do their own research, supplying background material on the plot such as characters' emails and voice mails.
“Unsane” is screening out of competition at the Berlinale, which will award its Golden and Silver Bear top prizes on Saturday among 19 contenders.