Ullmann had felt an unbearable responsibility when back in 1998 she was handed this guilt-ridden, frighteningly honest screenplay based on an incident of infidelity in Bergman’s life half a century ago. She tried to persuade him to direct Faithless himself, or at least oversee the pre- and post-production. But he insisted that Ullmann, who starred in Persona and other Bergman masterpieces and has a grown daughter from their long-ago relationship, make the movie herself, interpret it her way. He would watch Faithless only when it was finished.

Bergman’s stipulations: the remarkable Swedish actress Lena Endre was to play Marianne, the married woman with a daughter who becomes embroiled in the affair. Erland Josephson, from such Bergman classics as The Hour of the Wolf, Scenes from a Marriage, and Fanny and Alexander, was to be “Bergman,” the forlorn octogenarian thinking back, via flashbacks, to the key indiscretion of his life.

The actual event was in 1953. “He made Summer with Monika,” Ullmann explained, “and fell in love with the actress, Harriet Andersson. They went together to Paris, he came back to Sweden. He was married, had children, and said to his wife, ‘I’m leaving you.’ Faithless is about living through betrayal, loss.”

The script germinated for decades until Bergman found the actress who could make sense for him as the object of his adulterous desire. Lena Endre had performed for him at Stockholm’s Royal Dramatic Theatre in Romeo and Juliet, The Misanthrope, and Peer Gynt (she also played Eline Ormsdatter, Erlend’s married mistress, in Ullmann’s 1998 film Kristin Lavransdatter). “I think he didn’t know what face he needed to write this story of a woman’s emotions, but the memories of Lena were with him. She has everything he needed: discipline, experience, and she’s a great actor. If he hadn’t picked her, I would have picked her anyway.

“I’m a woman who has known Ingmar the most, 37 years. Erland has known him for more than 50 years and is the closest to him.” So close that Josephson could embody “Bergman” and the filmmaker could escape having to play himself on screen. “That way, Ingmar isn’t sitting here in Cannes. He’s scared of being found out, like we all are.”

Most important for Ullmann was that Bergman really liked the film when he saw the finished version. “Ingmar cried twice. First, when Marianne looks at her image in a mirror, a shot like the double mirror in Persona. Second, when Marianne comes home from the night of lovemaking.”

Where Ullmann’s direction took a personal turn was in her treatment of the daughter, nine-year-old Isabelle, who’s caught up in the consequences of her mother’s adultery. Ullmann hinted that there might be a repressed memory from Bergman’s boyhood: “Maybe he was that little child. I think that one time when he was very young, something bad happened to him.” In Bergman’s script, the little girl is talked about in a monologue but never appears on screen. “He didn’t think of putting in the child. He didn’t see the scale of suffering. I asked him about the children he had abandoned. But his generation didn’t see it as havoc.

“Though I had to be truthful to him, I also had to be true to myself. The scene I’m most proud of for Lena is when she talks to the child and cries about leaving. The first take she did as an actress, the second as the character.”

I wondered whether the actress who plays Isabelle, Michelle Gylemo, had been sheltered from this episode’s traumatic implications. Ullmann recalled, “I told the child that your parents are divorcing, your mother is leaving you. When we shot, I saw her tears. But she’s an actress! She screamed, ‘Did you like it? Should I do it again?’ ”

I’VE OFTEN MENTIONED the San Francisco Film Festival as a model for what our Boston one might be, with its ambitious program of documentaries, many highly political, and its emphasis on smart, formally stylish European and Asian films. But some see æsthetic trouble ahead: Peter Scarlet, the knowledgeable artistic director since 1984, has resigned his position to become the first American head of the Cinémathèque Française. Roxanne Messina Carter, the Los Angeles–based producer and writer who’s the new executive director of the overseeing San Francisco Film Society, is concerned, according to the Hollywood Reporter, with “building better relations with Hollywood studios — particularly the art-house units, including Miramax, Sony Pictures Classics, and Fine Line . . . ” And she’s Sundance Fest friendly.

Too friendly? What will happen at San Francisco? A happy beginning for Carter would be to appoint Rachel Rosen, the able and internationally respected assistant director of the fest, as Scarlet’s successor.