A precocious teenager begins an affair with her mom’s much older boyfriend in The Diary of a Teenage Girl, one of the standouts at this year’s Sundance film festival and one of the most realistic depictions of teenage sexuality to come out in a long time.

Newcomer Bel Powley sheds her native British accent to play curious 1970’s American teenager Minnie Goetz, a transcendent role that is sure to open doors for her in the future. Her genuine performance of sexual curiosity and coming-of-age is assisted by writer-director Marielle Heller. It’s her first time behind the camera but she works the film like a pro.

The duo recently visited San Francisco to promote The Diary of a Teenage Girl and this is a transcription of that conversation.

Q: Marielle, did you make any changes to the film since its Sundance premiere?

Marielle Heller: We didn’t have the opportunity and I knew the film was finished when we went to Sundance. We showed the film to friends and family but I don’t like the test screening model because altering the story according to what the audience wants it to be is never going to be as true as telling the story you want to tell. So I used myself as the test audience and asked myself if this was the movie I wanted to make. This movie is going to make audiences uncomfortable and that’s not something we want to change.

Q: You’re right. At Sundance, the woman to my left was shaking for most of the movie and the woman to the right was crying through most of the sex scenes.

Heller: There you go.

Bel Powley: It’s more interesting that way.

Heller: We were never trying to make a male audience comfortable with this story.

Q: Seeing how this is your first film as a director, what kinds of things did you pick up on set to make you more comfortable behind the camera.

Heller: Everything. Not being afraid to ask questions and embrace what you don’t know helped a lot.

Q: I’m guessing your work as an actress helped with that.

Heller: Oh yeah, I love actors. I don’t think all directors do love them to be honest, some of them are scared of actors. I think they have a fear of what an actor’s process is and how it works and if you don’t understand how actors approach their work and get into character then you’re both speaking different languages. I don’t know how every actor works but I can at least speak in similar terminology and be able to understand what the process requires.

Q: That’s interesting to hear and your work with Scott Frank on A Walk Among the Tombstones comes to mind. He has a reputation for being a very hands-on director. What was your working experience with him?

Heller: He was one of my advisors at the Sundance lab and that’s why I was in his movie. (laughs)

Q: Bel, what takeaways did you have working on this movie?

Powley: It was all great but it was really a blur because it all felt like doing a really long play. This was one of the first things where I’ve gotten to play the lead in something so I really had to enter this world and get into my character’s headspace for 24 days of shooting. I also stayed in my American accent while I was on set. Apart from that I can say shooting the sex scenes was fun. (laughs)

Heller: It’s funny, our first week on set we’re all in this big apartment and between takes Alexander Skarsgaard, Bel and I would all cuddle up in bed together. We would talk about the next scene and realize we all got comfortable fast. (laughs)

Q: You two are obviously getting a lot of questions on this press tour, is there one question you wish would go away?

Powley: What was it like to be naked and shoot the sex scenes? Obviously it’s awkward to be naked and shoot those scenes. I love talking about this movie but there’s more to this movie than just sex.

The Diary of a Teenage Girl is now playing in limited release.