June 27, 2014 5:15 pm

Colour science: Art analysis – pigments of the imagination

A scientific sideshow at a National Gallery exhibition demonstrates new techniques for investigating and altering our perception of colour

Visitors to London’s National Gallery can see an intriguing exhibition about the materials that artists have used over the centuries to create colour in their works. My colleague Jackie Wullschlager reviewed Making Colour in the FT last weekend but she did not mention a scientific sideshow next to the Sainsbury Wing galleries that demonstrates new techniques for investigating and altering our perception of colour.

This uses computer-controlled banks of light-emitting diodes (LEDs), operating at different wavelengths, to simulate a wide range of natural and artificial lighting conditions, from candlelight and old-fashioned incandescent bulbs to sunshine and moonlight.

Members of the audience are invited to respond during the show by pressing keys on an electronic pad – to show their preferences for seeing particular paintings under particular lighting conditions, and to indicate the extent to which they can distinguish colours as the illumination changes.

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Results from this audience-participation experiment will be analysed by Anya Hurlbert, professor of visual neuroscience at Newcastle University, who devised it. “With the new LED-based lighting technology we can put together an infinity of different spectra,” she says, “and mathematical techniques enable us to move smoothly between them as quickly or slowly as we like.”

Hurlbert, who is also a trustee of the National Gallery, is working with a Spanish company called Ledmotive, a recent spinout from the Catalonia Institute for Energy Research in Barcelona, to apply the technology. Intelligent LED lighting could greatly improve the viewing experience of gallery visitors, she says, by adjusting the illumination to suit individual paintings or groups of paintings.

Some works were painted by candlelight, for example, and some in daylight – and they may look better with the appropriate illumination. Then there is the issue that many pigments, particularly reds and blues, have lost colour over the years; of course clever LEDs cannot restore a painting’s original appearance but they can suggest the colouration better than standard gallery lighting.

The National Gallery has been analysing the physical and chemical composition of paintings since its scientific department was formed in 1934, using infrared and X-ray imaging, electron microscopy and mass spectrometry. The latest acquisition, bought in partnership with the Engineering and Physical Sciences Research Council, is a computer-controlled micro-positioning easel which can hold a painting, huge or tiny, and move it incrementally in minute steps.

Joseph Padfield with the National Gallery’s electronic easel©The National Gallery

Joseph Padfield with the National Gallery’s electronic easel. (Photograph: The National Gallery)

The £100,000 electronic easel, which is six metres wide, will enable gallery scientists to use many different kinds of instrument to scan pictures and learn about their structure and what needs to be done for their preservation. Ashok Roy, director of collections, says: “We expect to be able to acquire very high-resolution images in various parts of the spectrum that would be unobtainable without this technology, so it is a real advance in our imaging capabilities.”

A new option is hyperspectral imaging, which processes colour information from across the electromagnetic spectrum, “so you can take a picture of the painting and map where different materials have been used,” says Joseph Padfield, a conservation scientist at the museum. “This is not something you can do easily now. This easel will give us a platform from which to begin.”

“Making Colour” is at the National Gallery, London, until September 7

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