ART / In the Studio: Space is his subject, technology his chisel: Dalya Alberge removes her shoes to watch Ben Johnson, and his assistants, at work

For Ben Johnson, painting is not a solitary experience. His studio is positively crowded: in this white-walled, light- filled space in West London, he works with four assistants. While he is busy on a painting, one of his team might be transferring a Johnson drawing on to canvas, while another mixes colours and a third masks out areas to be spray-painted.

Although Johnson likes his studio full of life, he is an artist who rigorously paints out any sign of human beings from the buildings he depicts.

Without his assistants, he says, he would have to turn down commissions for his large canvases of minutely detailed, super-realist architectural subjects. For example, he explains, mixing colours is a job so intricate it takes a day to make up just six of them. An average painting will have a palette of 250 colours mixed by his assistants in the studio.

In the old workshop tradition, the master passed on his craft to the next generation. But Johnson (who was born in 1946, trained at the Royal College of Art and is represented in public collections including the Tate) has a different reason for working collaboratively. For him, it is an antidote to the over-emphasis in contemporary art on the 'personality cult'.

It is his way of bridging the divide between the arts and sciences - 'a divide that's one of the great tragedies of the 20th century.' Seeing architecture as 'a coming together of art and science,' he regularly works with computer scientists, historians, architects, engineers and mathematicians - exploring space, architectural space, perspective, geometry and light. It has been said that Johnson uses technology as a sculptor uses a chisel.

Inspired by 15th-century artists, Johnson explored the relationship between art and maths in Footfalls Echo, his 5m-wide canvas based on a 1460s panel attributed to Piero della Francesca. As Johnson explains, Piero had among his assistants a mathematician called Pacioli who developed a system of accounting still used today, and who collaborated with Leonardo in a visual exploration of 3-D geometry.

With his modern-day Paciolis, Johnson reconstructed every building in Piero's panel into a 3-D computer model. 'I wanted to represent a new painting made 500 years later than the original. I believe that the spirit is the same. In creating the model, we immediately realised that the space and perspective in Piero's panel in planning terms is nonsense, distorted to create a visual impact. It had been manipulated by a brilliant mathematician and artist.'

Back in the studio, Johnson researched the use of light and colour in the original, the colour of buildings in Italy and the Northern Italian light that floods them. He could then recreate the original building in painted form, but with a sense of contemplation.

Despite his continual exploration of architecture, Johnson insists that he is not a frustrated architect: his approach to space is entirely different, he explains. 'Architecture engulfs the viewer; paintings are looked at from the outside.'

Johnson's exploration of space is part of his everyday life. Anyone entering his studio has to take their shoes off and leave them outside. 'It marks the change from the outside world to the inside world,' he says. 'It's not precious, or about being ultra- clean. It's a ceremony of changing into another world.'

Johnson is exhibiting at the Fruitmarket Gallery, 29 Market St, Edinburgh (031-225 2383) until 26 March

(Photograph omitted)