Victor Sloan is best known for his extraordinary images of the marching season in Northern Ireland. Like all of his work, his Selected Works is made up of photographic images, but they are not straightforward photographs. Over the last 20 years, Sloan has been one of the most iconoclastic, experimental, innovative and audacious photographic artists at work, not just in Ireland but anywhere. He takes outrageous liberties with the nice, well-made, well-mannered photographic image, making of it something compromised and problematic.

These liberties begin with the use of the camera. When the painter Mark Joyce took up photography, he spoke about trying to introduce a different dynamic into the process, "shaking the camera around a bit, swilling the light around inside". As it happens, that's an uncannily accurate description of what Sloan does in many of his images, which distance themselves from a conventional pictorial aesthetic.

In his case, "swilling the light around" has to do with the rejection of neat, convenient narratives in terms of both form and content. Always he undercuts the authority of the photographic image. This interrogation of the medium reflects a questioning of what might be described as the narrative certainties that define political stances in Northern Ireland.

Sloan was born in Dungannon. His father had a shop in the town square. Later, during the Troubles, the square was several times a target for car bombers. "We'd have to discard masses of stock, all this confectionery, because it might be contaminated with bits of broken glass. There was a terrible feeling of waste, a kind of microcosm of the wider picture."

His mother was a keen photographer, "she photographed everyone who happened to call to the house," and she created an exceptional record of him and his siblings as they grew up.

Looking back over her old photographs, he also became aware of the poignance of the photographic image. These instants snatched from time actually accentuated the transience of life. "It brought home how fragile people are. They just disappear, they fade away."

SLOAN studied at Belfast College of Art and after that at Leeds, where he studied painting. "At that time there wasn't really the option of doing photography as part of a fine art course, it was something else." He was married, with children, when, in 1981, he paid a visit to Belfast Zoo. He brought a camera just to take some family snaps, but he was so appalled by the conditions of confinement that he instead took a series of photographs that seemed to more truthfully reflect the reality. These images encapsulate the basis of his subsequent approach.

The zoo could almost stand for Northern Ireland, and the difficulties of perception in Northern Ireland. Sloan accentuates these difficulties in the way he picks on surface intrusions: the glare of the flash, the grubby perspex sheeting. There is a sense that you can never take the surface at face value in Northern Ireland, there is always a lot going on beneath it, dark undercurrents. He then worked into the print surfaces. He wanted to exhibit the work and make it difficult for people to dismiss it as "just photographs".

Instead, they would have to contend with something that wasn't quite a photograph and wasn't quite a painting - a conundrum he has continued to present his audience with since.

From the zoo images onwards, he developed the idea of theatre and spectacle. People watching a fireworks display in Craigavon seem weirdly hypnotised by it. In the way Sloan delivers the image it is laced with unease. They could well be watching the violent spectacle of their own history unfolding around them. These ideas came to the fore when he began to make his marching season work.

Many of the images of Orange Order parades are among his most agitated and distressed in terms of surface incident. Scratched and scarred, they positively bristle with fear, anger, frustration and violence. He also approaches the essential elements of ritual, the Walk, the Platform and the Field as he approached Craigavon, in terms of a schematic social framework.

He is, though, non-prescriptive about the meanings of his work. He prefers that people interpret the images themselves, and is wary of pre-empting this process. Part of the logic of his approach, in questioning the possibility of objectivity and detachment, is that there may be entirely consistent meanings of which he is unaware. One implication that emerges from the marching season series, in his explorations of the Apprentice Boys parade in Derry, the Sham Fight at Scarva and the annual impasse at Drumcree, is that the ritualised re-enactment of a sanctified past, a past enshrined in tradition, is an almost superstitious way of warding off the possibility of future change. His documentation of the 1986 "Day of Action" , designed to bring down the Anglo-Irish Agreement, underlines this: it was, as he says, "a day of inaction" in his images, the source photographs for which were taken in Bangor. An out-of-season holiday resort is a place where things do not happen.

As Sloan's marching season images imply, the Sham Fight inevitably screens a real fight, the show-swords still wound.

The unresolved tensions and conflicts bound up in openended history cannot be satisfactorily contained in notionally benign parcels of identity, heritage and tradition. Inevitably, the problems will break through.

There are also dangers in the habitual presumption of moral superiority. The Circus series was made after he and his family happened to go on a Sunday, in Portadown, to see the American Circus Ltd. They found a group of protesters trying to prevent people going into the big top on the basis that, as their leader, Woolsey Smith put it, "the Sabbath is part of our heritage" and the circus represented a desecration of the Sabbath.

Sloan went on to photograph various circus performers. The implication of his images is a reversal of the protesters' logic. Just as the carnival props of the marchers refer to real underlying conflict, so he depicts highly skilled entertainers engaged in real acts of faith - faith in each other and in animals - on which their lives depend. It's tempting to relate these images to the acts of faith that subsequently led to the first faltering steps in the Peace Process, and the way the language of performance (with phrases such as "choreography", "timing", "stage-management", of things becoming "a circus") is routinely used to describe the political process.

Prior to the work he made about Drumcree, Sloan was involved in two projects abroad, at a disused Russian army base in Poland, and in Berlin, in the stadium built for the 1936 Olympic Games. The political theatre of the latter, and the notion of an aftermath in the former are obviously relevant to Northern Ireland, but they also broaden out Sloan's concerns, situating what might be regarded as local problems in a global context. It's as if he is asking, in this work, whether Northern Ireland is willing to grow up.

Victor Sloan, Selected Works 1980-2000 is at the Ormeau Baths Gallery, Belfast, until March 10th.