These are all relevant facts to bring up now, because new French-language documentary “Jane by Charlotte,” a portrait of the mother by the daughter, doesn’t discuss them. Perhaps operating under the assumption that no one unfamiliar with Birkin would watch a documentary about her, Gainsbourg instead veers too far to the other extreme, offering almost no context for their unstructured conversations, reminiscences, and chats.

Late in the film, Birkin speaks movingly about the days after the death of her oldest daughter Kate, when she couldn’t move beyond her own grief to the sadness of Charlotte and sister Lou. Casual viewers may have no idea when or how Kate died (it was in 2013, when she fell from a fourth-floor window), and Gainsbourg’s documentary is so dedicated to the conversational that backstory and exposition are impossible to interpolate. Certainly Birkin’s 12-year-long relationship with Serge Gainsbourg is never explored very deeply, despite a sequence at the film’s midpoint in which mother and daughter return to his pristinely preserved apartment. Once inside, as Gainsbourg proudly points out the long-expired (and exploded!) canned food items that are treated like artifacts, one wonders what the purpose of this visit — Birkin’s first in 30 years — could be. And more importantly, why has there been an almost pathological preservation quest, down to cigarette butts in ashtrays? Scattered among their exchanges of memories and impressions, Gainsbourg mentions possibly erecting Plexiglass to divide the rooms. “Aha!” we think. “This will be a museum!” Then no more is said about it, and it is up to Google to inform us that, yes, Maison Gainsbourg will be opened to the public beginning sometime in 2022. Clearly, “Jane by Charlotte” is not intended to be viewed as a traditional documentary, no matter how intimate. Which begs the question of what the film does intend to be. In the opening moments, Gainsbourg tells Birkin that she’s always felt a “shyness” between them, and Birkin agrees. When “Jane by Charlotte” takes flight, we feel as if we’re watching two accomplished adults really getting to know one another for the first time. But too often, the film and Gainsbourg are content simply to bask in Birkin’s warm presence. We garden with Birkin; we meet puppies with Birkin; we go to New York City for a concert with Birkin; we see Birkin posing during many, many photo shoots; but we never really hear from Birkin about how she became Jane Birkin, and the full ramifications of spending almost the entirety of her adult life in the public eye.

Occasionally a potent question is asked and answered, as when Birkin says she started taking sleeping pills at the age of 16 and never stopped. Or when, in voiceover, Birkin ruefully wonders about her parenting skills. Or when Birkin candidly chats about growing older and the aging process, wondering how she can love so many women whose faces look like “elephant’s knees” while still so chagrined by her her own wrinkles. But Gainsbourg’s film is willfully dedicated to not pursuing any single narrative, which means moments like these spring up and drift away. Divorced from all context — only fleetingly does Gainsbourg include photos or home movies, most movingly (and disturbingly) childhood gambols that prove to be the first video of Kate that Birkin has watched since her death — Birkin’s life is resolutely presented as in the now. She may discuss her inability to throw anything away, even a broken gift from Serge, but we don’t hear the story behind that gift. She has a memory for everything cluttering up her home, but she doesn’t share them and Gainsbourg never asks. The moments that linger are the moments when Gainsbourg turns the film wholly subjective. Wry and wise voiceovers juxtaposed with gorgeous scenery; a moving monologue from Gainsbourg while the camera remains focused on her mother that closes the film. Gainsbourg’s purpose in filming “Jane by Charlotte” may have been to look at and truly see her mother in a new way, and no doubt she succeeded. But as they bond and converse, their conversations take on a closed aspect, never inviting us in to their increasingly close relationship. We remain watchers, appreciative of but never truly understanding the magic of Jane Birkin. “Jane by Charlotte” will be released in theaters March 18.

Grade: C

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