There's a lot more to photographing buildings than meets the eye, writes Emma Cullinan.

Gerry O'Leary took a roundabout route to becoming an architectural photographer yet his early experience, as a building surveyor and construction manager, hasn't been wasted. It helped to give him an eye for buildings, from the shapes down to the details.

"Honing in on a detail often makes a more exciting image," he says. "As a construction manager, I spent almost nine years interpreting building details so I always look out for interesting details and think about the length of time it took the architect to draw them."

We have become a visual society. In the past, newspaper pages contained only columns of stories, yet now they are dominated by an arresting picture, and architecture books, which used to comprise text and line drawings, are now laced with photography.

This has developed alongside the growth of marketing and design, with eccentrically clad women demanding attention on catwalks. It seems only natural, then, that fashion designers have been asked to create interiors - sumptuous photographs of new hotels can sell rooms in the same way that they sell clothes.

"As a society we are more image conscious than ever," says O'Leary. "That includes our clothes, cars, homes, gardens and places of work. Even architecture is becoming 'designer' with the likes of John Rocha and Philip Treacy having a hand in design. Much of this is generated by photography feeding into the advertising and marketing frenzy. Estate agents and property developers have discarded the 'DIY approach' in favour of professional photography and architects realise the value of arresting imagery."

Architectural and interiors photography is a specialised discipline that involves technical know-how, expensive equipment, elbow grease and time.

House shoots for interiors magazines take the best part of a day and often involve the removal of great swathes of unappetising furniture out of the way of the lens. The camera - despite the familiar saying - can be economical with the truth by ignoring nasty elements. That photo of a beautiful window detail, illuminating the corner of a bed and bedside table adorned with a vase of flowers and a classic design tome leaves out the junk piled up beside a hideous chair nearby. "I move furniture around and place it strategically in the frame," says O'Leary.

While working as a building surveyor he admits that he was a bit of an anorak when it came to his photographic hobby; reeling off F-stops and light readings like a true shutter bug. What makes a great architectural photographer, he says, is to take all that as read and go beyond.

"The technical aspects, such as exposure and sharpness, are a prerequisite; the key to a successful image is its compositional strength. To be able to take a good photograph you must understand its component parts and have an innate ability to assemble them imaginatively. I view architectural photography as a series of shapes, colours, light and shade framed within a canvas to give a perfect sense of balance.

"I'm meticulous to the point of being obsessive about composition, moving the camera repeatedly, up and down left and right, aligning verticals [ie, keeping walls and doors straight rather than letting them splay by tilting the camera] and seeking orthogonal vantage points."

It also helps to be a weather expert and know about building orientation. "The sun moves at 15 degrees per hour relative to the earth," he explains, illustrating how he decides at what time to snap bits of buildings. Many buildings are in shadow during winter, when the sun is low, he says, and north-facing elevations can spend eight months of the year in the shade.

"Buildings metamorphose every hour of the day and every season of the year," he says. For this reason, O'Leary doesn't take on projects overseas, as he can't be sure that the weather will be right when his plane lands. In Ireland he's happy to wait (within reason) for the right conditions. He finds that it's best to shoot exteriors in the sun and interiors on duller days which, surprisingly, achieves a good balance between the two.

Despite having a clutch of photography awards to his name and a role as the first overseas president of the UK Master Photographers Association, O'Leary says that if he'd realised just how difficult it would be setting up on his own, he never would have done it.

"I was naive," says the man who decided to give up his former life and become a photographer just as his wife was expecting their first child, in 1993. He even went on the dole for a while but his timing turned out to be providential, as his decision to be an architectural photographer tied in with Ireland's building boom, the rise in the importance of image (and the image), the improvement in building design and a heightened interest in architecture.

Only three years ago the Irish Professional Photographer's Association introduced an "Architectural Photographer of the Year" category and O'Leary has picked up the award every year since then.

Yet, when he started around 13 years ago, the notion of taking professional photographs of buildings was a strange one in Ireland, he says. Now there is a clutch of architectural photographers based in Ireland, including Ros Kavanagh, Paul Tierney and Phil Lauterbach.