Outside Edge: Julie Hedgecoe knows Norwich's nodules better than anyone alive. Anna Green reports

MEET THE woman who spent three years photographing roof bosses. Julie Hedgecoe lives in East Anglia where she likes the light and the wide open skies. But when the historian Martial Rose suggested getting together to provide a record of Norwich Cathedral's medieval roof bosses (the sculpted nodules decorating the ceiling), she was intrigued and, though working with still lives at the time, dropped what she was doing. 'Seventy foot down, these bosses are just coloured blobs,' Hedgecoe explains, 'simply there for the glory of God. But it struck me what a privilege it would be to view one of these medieval carvings close up.'

Norwich Cathedral has about 1,000 roof bosses and, apart from the ones in the cloisters which you can study by standing on a chair, they're not exactly accessible. To begin with, Hedgecoe had no idea how to 'unravel all those little dots'. Scaffolding, which would need erecting and dismantling as she progressed, was too expensive (the project was funded, thinly, by local charities). An electronically operated high-rise platform wouldn't fit in the transepts. At one point she scaled the organ, and dropped a vital screw down one of its longest pipes. There was only one option: 'A miniature format camera placed on the floor with the longest lens available.'

Step one in the 45- to 90-minute process of shooting a 'straightforward' carving was lying on her back (on a sleeping bag for comfort) with a pair of binoculars trained on the roof in search of the boss. Then she'd mark a spot on the floor where the camera should be placed and, with assistance - her 800mm Leitz lens was very heavy - lug tripod, lens and camera over to it. The axis of the boss had to be squared very carefully in the frame. The tiniest movement could lose the whole boss. It was vital to get the very best angle, as there were only funds for one shot of each. The light inside the cathedral was a problem, so she roped up film lights - one in the triforium and one on the floor - using corrective colour gels to counteract the green glow from the upper windows. Positioning had to be precise: the carvings cast small shadows and it was important that the light should catch all the facets and fissures.

Hedgecoe found herself falling in love with the bosses. 'At first I thought they were nave,' she admits, 'remarkable only for the quaint anachronisms and bright colours. But Martial Rose helped me see beyond that and I began to be fascinated by the details.' Together they speculated on the different hands at work - the bosses were worked on over a 60-year period, between 1446 and 1509. Was it the master carver who varied the faces and gestures of the mourners around Herod's deathbed? Were the most dramatic scenes exercised by local sculptors familiar with Norwich mystery plays? Most fascinating throughout was the discovery of local influence on religious vision: Moses wears not Jewish sandals, but East Anglian boots; Joseph sits in an Egyptian prison that looks just like Norwich stocks; Delilah sets to on Samson's hair with a pair of sheep shears. 'Working these things out,' says Hedgecoe, 'was just wonderfully exciting.'

Six hundred of Norwich's roof bosses had been captured on film when the money ran out. That means 400 still to go, and Hedgecoe is determined to finish the task somehow before she returns to photographing still lives and the wide open fields. But she does have the odd moment of doubt: 'Sometimes, just for a short while, I feel guilty at intruding,' she says. 'And I think perhaps they should be left up there in all their stillness. But then I think that's what history's all about, isn't it? The endless uncovering of details. Just like photography really.'

Next week: the agent who put her life savings on ice.