By BBC News Online's Alfred Hermida

Digital imaging is revolutionising the way classical works of art are being preserved for future generations.

The National Gallery in London, UK, is leading the way in the use of this technology to make high quality digital reproductions of paintings.

For the past 10 years, it has been developing a system to monitor tiny changes in the artworks and build up a precise record of the colour of paintings to see if there are any changes over time.

"It means we can be a lot more confident that we will notice if there any changes going on in the paintings we are looking at," explained Dr David Saunders, conservation scientist at the National Gallery.

"In the past, the potential for error was high," he told the BBC's Go Digital programme.

Focus on colours

During 2001, the National Gallery made digital copies of its major paintings. It is now aiming to digitise its entire collection by the end of this year.

Camera captures 10,000 by 10,000 pixels

For the project, Dr Saunders had to persuade his colleagues at the National Gallery to invest in a series of expensive and untested imaging technologies.

The job has fallen to Vasari (Visual Art System for Archiving and Retrieval of Images), which uses what is called a colourimetric imaging system.

A special digital camera is used to capture each square metre of a painting's surface with a resolution of at least 10,000 by 10,000 pixels

"The kind of camera you would buy in a shop measures just red, green and blue," said Dr Saunders. "But this doesn't really provide us with enough information. So the present system uses seven colour bands, like the seven colours of the rainbow."

Invaluable record

The imaging system enables researchers to monitor tiny changes in colour or surface texture without handling the painting.

The camera is controlled by computer

It means they can build up a permanent record of the state of paintings.

Future images can then be compared to determine if there has been any damage caused to artworks in storage or when they are moved for exhibition.

The system was developed in a project sponsored by the European Community.

Several other galleries are adopting the technology, including the Uffizi Gallery in Florence, as it provides an invaluable record of the artwork for curators and art historians.