This documentary leaves us in no doubt at all about the Observer photographer Jane Bown's brilliance.
Her black-and-white portraits, whose subjects range from Bono to Samuel Beckett, from Edith Sitwell to Björk, are wonderfully revealing. She has a genius for framing, for using natural light and for winning the trust of the most narcissistic or hostile interviewees.
The film-makers show off her work to fine effect, pausing long enough for us to appreciate their craft and detail. As portrayed here, Bown comes across as an eccentric, self-effacing character with a hint of Miss Marple about her.
The doc deals sensitively with the extraordinary circumstances of her childhood and features illuminating contributions from journalists and fellow photographers, Rankin and Don McCullin among them.
Even so, this is not especially cinematic fare. With its interviews and talking-heads format, it is closer to a TV arts programme than to film-making for the big screen.