Finding Vivian Maier

We've all had one of those moments when we've opened a second-hand book and photograph placeholder or other personal item has slipped out. As we gaze at the unknown face, we wonder who is in the frame and who wielded the camera. This, although on a slightly more deliberate and grander scale, is what happened to John Maloof. A serial bidder at auctions, he shelled out on a whim for a large box of negatives - one of several for sale on that particular day - and after letting them gather dust, finally decided to scan a handful of them and upload them to photosharing website Flickr.

The photos were so striking that he decided to try to find out more about the photographer Vivian Maier but a Google search yielded nothing. Two years later, a second search chanced upon her recent obituary and the ball was set in motion for what would become something of an obsession. Maier, it turns out, was not a photographer who had simply never quite made it but a children's nanny who, although never without her camera, seems to have very rarely shared her work with others.

Maloof and co-director Charlie Siskell take a traditional approach to their documentary, rebuilding Maier's life, moving between her street-captured images and talking heads of some of those people who hired her or fell under her care.

The photos themselves are striking snapshots of humanity - often collected by Maier in the downbeat areas of Chicago, with a reluctant child or two in tow. There are thousands of pictures, ranging from down and outs on street corners to children caught in a moment of tears. Captured using a Rolleiflex - a boxy camera that is distinguished by the fact that it is held at waist height while the photographer looks down into the lens from the top of it - this means that the children or those on the street seem to always be on her level, their gaze straight at the camera, while the shots of adults as they walk past loom large and domineeringly in comparison.

As the film progresses and Maloof - who acts as a pleasant, informative guide - begins to peel back Maier's surprising family history, a more troubled picture also emerges as we learn that she was a packrat, whose bedrooms tended to be filled with massive stacks of old newspapers and who hoarded virtually ever geegaw or receipt stub that came her way. The snapshots offered by the various children who passed through her care also range from those who thought she was terrific to those who believed she was merely eccentric and one or two who found her outright cruel.

What is almost as interesting is the portrait that emerges of people's opinions of 'creatives' or at least the opinions of those represented here, as they adhere strongly to cliches regarding class mobilility and what drives an artist. The idea that this nanny had the tenacity to keep her talent to herself seems to be an affront to many, somehow against an unwritten rule about domestics knowing their place. Someone also asks in wonderment, "What's the point of taking it if no one sees it?", as though the idea of Maier enjoying her hobby for its own sake is ludicrous.

Throughout it all there are definitely glimpses of Maier, not least in her own photos - where she often appears in half shadow, or multiple reflection - but questions remain. Maloof, though earnest, has undeniable skin in the game as the owner of Maier's archive, so it feels as though the levels of 'mystique' are intended to remain high - this means, for example, that although it is revealed that two of her former wards paid for her flat in retirement, we never see them talking about it to camera. These sort of empty spaces hang around the edges of the frame of the film and though it's never less than engaging, there's a nagging sense of missing out on the bigger picture.