Sam Taylor-Johnson has spoken about the frustration of working on the Fifty Shades of Grey adaptation, saying she is "literally going out of" her mind.

The director took the helm for the highly-anticipated adaptation of E.L. James' novel, but felt the pressure while shooting the film.

She told Red magazine: "I want to protect my vision and that's the hardest thing. There are so many voices. You have to try and keep all those people at bay. You think, you hired me because I'm a creative artist with a vision. Don't try and knock it out of me."

Taylor-Johnson also explained that maintaining control over the production was a struggle, explaining: "I'm literally going out of my mind.

"I have seen this film over a thousand times and I'm now in a blancmange. But the nuances within-the tiniest shift, look, blink of an eye-can make all the difference and flip it into the wrong territory. It's like walking a knife edge."

However, the director praised the film's leading stars, Jamie Dornan and Dakota Johnson, saying: "Dakota is fantastic. She has that rare knit of fragility, vulnerability, naivety, yet she's really strong.

"And Jamie's funny because he doesn't seem to feel any of the pressure. Or show he feels it. Everything washes over him and he's constantly happy. He's such a sweet and lovely man."

Fifty Shades of Grey is out in cinemas on February 13, 2015.