You’ll know at least one photograph by Jane Bown; she took the picture of Samuel Beckett staring into the camera like an eagle in a white knitted polo neck. And it’s in the small exhibition of portraits taken by her for The Observer at the Guardian Offices by Kings Cross Station marking the release of a film documentary about her.

I managed to get along today at lunchtime, as it would be my last chance to go before it finishes on Saturday. I saw an earlier exhibition that went with the book Unknown Bown and which contained pictures (often) taken to finish off the roll in her camera as she returned from an assignment. They were lovely, as old photos of ordinary things, well taken, often are but the current exhibition gives a chance to see very large prints of her work for the paper lots of which are images lodged somewhere in my head along with the Beckett from reading the Observer Sunday after Sunday: Björk with her hands over her face; Cilla Black half-rising out of her seat, knees together and elbows out as she takes a sip from a plastic cup; Bertrand Russell in profile; PJ Harvey in an open white shirt and black bra looking straight through the camera and the you behind the photographer…

The pictures are taken with available light, in contrasty black and white. They are immediate and look unposed, moments caught during an interview, or before it, or after. They don’t flatter, but the subjects still look good. I can imagine that Cilla wasn’t too keen on the her picture from 1967, but there is a wonderful foal-ishness to her ungainly pose and you can see where some of her drink has spilt onto the vinyl couch she’s rising from; it feels real, a moment captured.

The size of the prints reveals imperfections that would be lost when reduced to dots and printed on newsprint (the picture of Thatcher is really quite soft: the sharp area is somewhere between her eyes and her ears; you can imagine her lunge-ing towards the camera a lecture brewing) but also just how powerful they are as representations of people you think you know. And when there are no imperfections, they’re brilliant – Becket’s eyes are like crystal, studded with grain; the black of the alley behind him is really black, setting off his hair and the poloneck and the pewter contours of his face.

Her style here suits birdy, beaky people – Bertrand Russell, John Lennon, Lucien Freud, Francis Bacon, Jean Cocteau and the triangular head of his siamese cat all are splendid –  but of the pictures that were new to me, I particularly liked a tight closeup of Boris Karloff, looking both like the lovechild of Omar Sharif and Windsor Davies and totally like himself (from 1955) and this one:

a sour-looking Bob Hope and Anita Ekberg on a film set in 1950, looking as bored and fed up as people kept waiting on a set can do; it could be a still, if it wasn’t for Ekberg’s direct gaze at the camera and the out of focus lighting stands and mic boom creating a distance between us and them; Bown is observing and we are standing with her. The picture is both real and a fabrication; there is a sense of story and a sense of being there. I like it lots.