Tackling the story of one of France's most beloved personalities is a daunting task, especially in a country which does not revere the biopic. But a few years ago, as Olivier Dahan rummaged through some photos in a book store, he was bitten by the Edith Piaf bug.

"I came across a photo of her at a young age and realised I didn't know a lot about her. That photo was really the inspiration," says the director. He called his producer and "in half an hour the project was done".

Perhaps he is slightly exaggerating the timescale, but Dahan was given an immediate go-ahead from producer Alain Goldman, with whom he had collaborated on 2004's Crimson Rivers II: Angels Of The Apocalypse. Dahan says he was not looking for any specific kind of project but with La Vie En Rose he adds another genre to his resume, which includes family drama (Le Petit Poucet), crime drama (Deja Mort), drama (La Vie Promise) and action-thriller (Crimson Rivers II).

Dahan knew he did not want to do a classic biopic and set about writing a story that would mix different periods of Piaf's life. During the writing process he thought about the lead role and, although he did not know Marion Cotillard personally, he began to see her as Piaf.

To be sure, Dahan "waited a year to finish the script before I called her", but Cotillard had no such reservations, jumping straight on board, alongside Gerard Depardieu, Sylvie Testud, Jean-Paul Rouve and Emmanuelle Seigner.

The film was made for around $25m, shooting in a studio in Prague and on location in Paris and California. "It wasn't easy but everything went very well," Dahan says. "We had a good star shining on us."

Nine months of post-production followed, with a lot of editing. As all of the music in the film is sung by Piaf herself, negotiating the rights was also an issue. Dahan says the producers hammered out a deal with Piaf's descendants and music companies over a full year, and that a large amount of money eventually changed hands.

When asked why no-one had made a definitive Edith Piaf movie before, Dahan says: "Probably because it's very complicated. It's risky to tell her story. I think people have been scared before. I thought about it a little but it didn't scare me."

The film, which screened in competition at the Berlin film festival, has sold worldwide and opened in Paris on Valentine's Day, taking just under $12m in its opening week. This summer Picturehouse will distribute it in the US.

Dahan is hoping to support the film through its international rollout and is especially happy about going to the US. Set up now with an agent at ICM, he is looking for a project in English - but on a much smaller scale.

LA VIE EN ROSE (LA MOME)
Edith Piaf's battle to sing, survive, live and love.
Budget: $25m
Producers: Legende Entreprises, Okko Production, Songbird Pictures
Sales agent: TF1 International
Main cast: Marion Cotillard, Gerard Depardieu, Sylvie Testud, Jean-Paul Rouve, Emmanuelle Seigner, Clotilde Courau, Pascal Greggory.