Carey Mulligan always tries to do the ''bare minimum'' on camera.

The 34-year-old star thinks her 'Promising Young Woman' director Emerald Fennell's background as an actress gave her an extra ''edge'' and the filmmaker pushed her to ''cross the line'' more in the movie, which differed from her own usual approach to a character.

Asked if she felt Emerald's acting experience gave her an added edge as a director, she said: ''Yeah, I think so. I just think she's got a lot of experience.

''She's an actor, she's a writer, she's a director and she's got this unique lens through which she views the world, and her sense of humour is really dark and punchy.

''A lot of what we did was cross the line and then draw back from it a little bit.

''My tendency is always - and I always say this to directors - I'm going to try and do less and if you need me to do more, you need to give me a bit of a prompt, because my instinct is to do the bare minimum to make things truthful.''

Carey was happy to give ''more'' in her performance because she felt ''protected'' by the director because she promised to ''cut'' any footage that ''sucked''.

Speaking to Margot Robbie for Australia's Vogue magazine, Carey said: ''This is what I figured out on this job playing Cassie.

''In some of those moments when I was pulling back, Emerald was pushing me to be more.

''She was like, 'Life can be really extreme sometimes and you're allowed to react in an extreme way.'

''All my favourite directors have been people who I've given trust to. I know they're going to protect me. She was always saying: 'I'm not going to let you look like a t**t in the editing room, so if it sucks we'll just cut it and it won't be in the film.' ''