Olivia Hetreed adapted Tracy Chevalier's novel Girl with a Pearl Earring for the big screen. Here she talks to iVillage about the process of turning a novel into a feature film

How closely did you work with Tracy Chevalier? Did you lock horns over anything in particular or was it a fairly easy working relationship?
I met Tracy right at the beginning of the project and we were both quite nervous. But, she said the textbook-perfect thing for an author, which was, "I don't want to write the screenplay. I completely hand this over to you. If you want to ask me any questions, please do. Otherwise, just take it away and make something of it." It was formidable of her to actually let go completely. I did come back to her with questions, but they weren't the sort of questions she was expecting. They were practical questions - "Which painting was this that you mention was on that wall, would they really have had a cellar in a house next to a canal?" They were very specific.

We started corresponding by email and turned into pen pals over the next year. As a courtesy I sent her the first draft and, later, Peter's draft before we started filming. Thank God she liked them. She said that when she read that first draft she felt as if she had vertigo, because it was as though I'd been inside her head. I think we do look at things in the same way, so it was very easy for me to take her work and feel that I was in sync with it.

Were you a fan of Vermeer's paintings before getting involved with the book?
I was in that general way in that it's hard to look at a Vermeer and not be a fan. I hadn't seen Girl With A Pearl Earring for real before I started work on it. One of the first things I did was I went to the Hague and stood in this small room in the corner of the Maurtizhuis, which has Girl With A Pearl Earring on one wall, and the view of Delft on the opposite wall. And you can really spend your life in that room. They are such beautiful paintings. And, although they're beautiful in reproduction, they are astonishingly more beautiful in the 'flesh'.

However fictitious this story is, you feel like you have some kind of insight. I feel as though I've deconstructed the paintings down to their bare bones and worked out how he painted them. So, just as doing a piece of literary criticism takes you deeper into a poem, if it works well, I feel like I know the paintings in a way that would be hard to do just by going round an art gallery. It's a much more intimate involvement.

How did you start turning the novel into a film?
I read it with the possibility of turning it into a film but, actually, the first time I read it, I just read it and I was completely enthralled. I was just keen to get to the end of the story to know what was going to happen. And then I thought, this is a movie. I could completely see the film in it from the first reading, which isn't always the case. It's an incredibly tight story, but it wasn't until later on that I realised how clever Tracy had been. The novel has an endlessly layered time scheme and she's constantly jumping to and fro from different perspectives, so I had to think carefully about how to approach it.

How did you decide which characters to drop or merge?
Well, there's a practical consideration. Anything that is purely tangential and doesn't really take you anywhere has to be dropped. As I progress through the draft of a script it tends to move further away from the book, so that it's a gradual freeing of the book. Peter is also a fantastic and ruthless editor and he took anything out that wasn't really making the story go forward.

What was the motivation behind changing the ending ever so slightly?
The end of the book is a 'ten years later' jump. You can do that in a book because you can go back and you can reflect. But in a film you are strictly in the linear experience. Having a 'ten years later' at the end of this very intense story between two people would ostensibly let the tension out. And there was also a practical consideration, which is that you've got a 17 year-old girl and you're gonna suddenly make her look 30. It's a bit creaky. So I had both an aesthetic and a very practical consideration in mind.

I wanted to convey the sense of openness and possibility about the ending. I think what the book does, and what I didn't wan t the film to do, is to tie everything up completely so that you know what's happened and where everybody's gone. I liked the fact that this was the beginning of Griet's life and that she had potential to do things with it.

What kind of books do you like reading?
I read a lot and pretty widely. I read a lot of biography now, which I think is one of those things you grow into somehow. I remember hearing other people saying they read biography and finding it so dull in my twenties, and now I've begun to find it more interesting myself. Partly because what's thrilling about fiction is that it's organisation, and biography is obviously lacking in organisation. Fiction-wise, I love Coetze, I love Henry James, and I'm just reading The Life of Pi, which is great fun.

Is it hard for you to read for pleasure? Do you find that you're constantly coming up with ways books can be adapted for the screen?
Yes and no. If a book is good enough you then forget you are a screenwriter. If I'm really enjoying the book, although I might have that thought process going on somewhere, it's not bothering me. Whereas, if I'm reading something that someone sent me and I'm not really enjoying it, then I start to wonder, 'well they must have thought there's a movie in here somewhere. Why am I not seeing it, and what could it be?' And then I become obsessed with that, rather than just getting on with the book. There are some books that I read and it's a pleasure for me to see that they are 'unfilmable'. It's a personal predilection to look at a book and think, 'nah, you couldn't do that one,' but they're not necessarily my favourite books.

Girl With A Pearl Earring is out on January 16th