A world divided: Brighton Photo Biennial gets to grips with poverty, protest and politics

Brighton's extraordinary Photo Biennial is in its fifth season, and this year it is edgier than ever. With every archive or photographer they select, the curators needle away at the question, what is the point of photography today? What sort of truth can it tell? What function can it have beyond mere wallpaper?

A century ago, these questions were easy to answer. The value of a figure such as Eugène Atget, lugging his tripod and plate camera around the lanes of Montmartre to capture his images of the city, was beyond doubt. Fifty years ago, Don McCullin and Larry Burrows, dodging enemy fire in Vietnam, were doing something whose significance was equally easy to understand. But today? We are saturated with images every conscious moment of our lives. Photography has become ubiquitous and inescapable, and as a result the professional photographer is an endangered species: who needs him when we all carry amazing cameras in our pockets? More to the point, we no longer appreciate what the professionals can do that we can't. The very idea of a beautiful photograph risks losing all meaning.

So what's the point? Which images have value beyond dispute?

Seventeen years ago, three professional photographers approached several dozen children and teenagers sleeping rough in the Brazilian town of Belo Horizonte and offered them "point and click" cameras. "We would supply the cameras, process the films and talk with them about the images and experiences," one of the three recalls. "We simply wanted to make this possible, to see what would happen."

The project, still underway, has had its casualties. "Most of the original 55 participants have died, disappeared or been sent to prison," they say. "Several have died from Aids-related illnesses or been run over by traffic. Some have been killed in fights, or may have been murdered." The professionals are hazy about the identities of the photographers and believe many gave them false names. They are hazy, too, about the fates of the ones who disappear, as the kids are cagey with details. We are left with images that in some cases are all that remain of unknown individuals who have since vanished. Their snaps – whether interesting or boring, emotional or flat – have value beyond doubt, as the only proof that they ever lived.

But what other value can today's photography aspire to?

The theme of this year's Biennial is "the politics of space". We live in an age both k of unique freedom and unique constriction. Technology has given us unprecedented capacities, but it also constrains us, confining us within a digital panopticon, a virtual equivalent of those cunningly designed circular colonial prisons where all the inmates were visible to the authorities all the time. The smartphones in our pockets shackle us ever more firmly to the organs of control. As Bradley Garrett, one of the contributors to the Brighton Biennial, puts it, looking forward a year or two, "drones will dominate the skyline, CCTV cameras will recognise our faces, wirelessly pinging the data from the time-saving Oyster card in our pocket, triangulating our position with the convenient smartphone also in our pocket, a phone built by the same corporations that own our government, the same corporations that are building a new city we have no right to access."

The intrepid photographers of the past brought back strange images from far horizons. But now the whole world has been zoned "commercial", nothing is exotic any more. Everywhere is constrained by the same rules. Where do we go to see those rules put into force? Where can the photographer thrust his lens to shoot what's really going on?

Taking its cue from the Occupy movement and the Arab Spring, Brighton this year focuses on the question, "How is public space constructed, controlled and contested?" In a recent talk, the philosopher George Caffentzis said, "The truly subversive intent of the Occupy sites is to transform public space into commons. A public space is ultimately a space owned... by the state. A common space, in contrast, is opened by those who occupy it." The idea of commons – an idea embodied both in the occupation of the London Stock Exchange and the occupation of Tahrir Square – is a rejection of the property principle on which the system controlling our world depends.

You cannot create commons by pointing a lens at something. But the camera can reveal the reverse process: how the commons of a desert, say, is slashed by highways, hijacked for advertising imagery, and progressively walled off for new suburbs or a surreally green golf course. It can witness the spasmodic but inspiring attempts to roll back the tide, from the long tradition of Brighton street protest to the occupiers of "Goldman Sucks". And it can bestow immortality on street kids whose lives meant nothing to practically anyone else while they still lived.

The Brighton Photography Biennial runs from 6 October to 4 November, see bpb.org.uk for further details