Filming Unsane on an iPhone was personal breakthrough for Soderbergh

US director says it is the kind of film he has been trying to make 'for years'

US director Steven Soderbergh continues to be at the forefront of visual storytelling, nearly 30 years since he won the Palme d'Or with his 1989 debut film Sex, Lies, And Videotape.

From feature films to traditional television and experimental hybrids such as interactive series Mosaic, the 55-year-old seems prepared to try anything.

Unsane is an intimate, immersive and unsettling story of a troubled young professional (Claire Foy) who is drawn into a living nightmare after she seeks psychiatric help in a new city.

Opening here tomorrow, the movie took advantage of technology and Soderbergh's evolving working processes to come together quickly. Also, it was shot entirely on an iPhone 7 Plus - with lenses and a rig - using natural light.

On whether it was an adjustment for the cast, Soderbergh said: "You would have to ask them if it was weird to look in front of them and see this tiny thing. They didn't seem to care as far as I could tell. They certainly liked the efficiency of it.

"I viewed it as a significant moment in my own personal journey. There were so many aspects of working with this technology that were positive. I knew immediately that I was going to do it again."

Is part of what motivates you the desire to do something different?

"Unsane is a kind of film I was trying to make for years... And it happened to sync up with a moment in time where I had done enough testing with this new technology to feel like, 'I am ready to make a movie using this and this is the perfect movie to do it with.'

"And my continual attempt, in terms of process and shooting style, is to distil everything down to its absolute essence - that there is nothing wasted and every shot, every cut, has a purpose... I am constantly trying to analyse: How can I make this thing just all muscle-mass?"

Foy has an amazing ability to convey internal conflict. Did you know her from (the Netflix series) The Crown?

"I had seen that and I had seen (British miniseries) Wolf Hall. But one of the things I loved about the idea of her doing this is it seemed like a great opportunity to sort of annihilate her work on The Crown. When I watch the movie, I forget it is Claire. She is so different in this that I literally at times forget... (she is) who we know as Queen Elizabeth."

Unsane deals with a threat to a woman and feels particularly timely. Did that play into the decision to do this?

"This came from (writers) Jonathan (Bernstein) and James (Greer). I don't know whether or not they had a discussion about the gender power dynamics that exist nowadays and the fact that technology increases those inequities, when somebody predatory uses the technology to their own end.

"I don't know if they sat around saying we should do something... that has some sort of quiet resonance so when people leave the theatre, it doesn't disappear from their minds. I was certainly happy the movie had these things going on that were leaking in from the corners."

Was your intent going into Unsane to make a horror film? It could also be called a psychological thriller.

"When people ask me I say, 'Well if you're a woman, it's a horror film. If you're a guy, it's a primer on how to meet your soul mate.' But yeah, I think it depends. I think the term horror conjures a certain kind of film for some people.

"I wanted to be careful that I wasn't creating an expectation that was inaccurate. I view it more as a psychological thriller, but I also know from talking to the women who have seen the film that their response to it is extremely visceral. They view it as a waking nightmare."