In 1964, the ex-Harper's Bazaar photographer Nat Finkelstein bowled up at Andy Warhol's Factory to shoot a documentary. Three years later, he reeled out with a unique archive of images of the artists and musicians who defined the 1960s.

Taking candid portraits of such narcissistic subjects required the stealth of a cat, but Warhol's own ubiquitous camera probably made invisibility easier.

Redferns' exhibition includes both portraits and, unusually, people at work: the Velvet Underground setting up equipment, Warhol arranging helium balloons for a party, reading in a chair - a scene reproduced in the recent Edie Sedgwick biopic Factory Girl, for which Finkelstein was a consultant.

Dominating the room are Warhol's shades and thatch, Bob Dylan's skinny suits and cigarettes and Sedgwick's innocent beauty.

Following the movie, she is the star attraction and is captured in perfectly textured close-ups and profiles (Finkelstein's favoured pose), her innocence still intact.

The "crutch shot" in a crumpled lamé shift is a startling contrast to the show's other work. Finkelstein captures beautifully but never penetrates the cool elegance and intelligence of the Velvets' singer, Nico, or the iconic, frozen conversation between Warhol and Dylan (in profile), who are separated by a huge silkscreen of Elvis Presley pointing a gun at his camera.

The lasting power of these images relies on meticulous printing appropriate to Warhol's perfectionism. They commemorate the many characters described by the photographer: "Some guests left in limousines, some in ambulances, others never found the door."

• Until 12 May. Information: 020 7792 9914, www.redferns.com