by Jo Marchant
Uniform lighting conditions appear rough and almost unnatural
(Image: Alexandrino Goncalves)
From cave paintings to Roman mosaics, our perception of archaeological artefacts is affected by how they are lit - which is usually by bright modern lights. As a result, the way we see them may bear little resemblance to how they would have looked to the people who created them.
Alan Chalmers of the Digital Laboratory at the University of Warwick, UK, wants to fix that. He is working with computer scientists and archaeologists at the Roman site of Conimbriga in Portugal to come up with computer reconstructions that take account of the lighting conditions of the time. "We want a research tool, not just a pretty picture," he says.
Conimbriga was known for its splendid House of Fountains, and many of the mosaics and frescoes at this richly decorated villa are still intact. These include a hunting scene on the floor of the sala da caçada or hunting room.
Most computer reconstructions of the way archaeological sites would have looked assume uniform lighting conditions, and even when given this treatment, the sala da caçada looks impressive enough. But as Chalmers points out, the room would have normally have been lit by a series of lamps or lucernas that burned olive oil, which would give it a quite different look.
Computer science students at the Polytechnic Institute of Leiria and the University of Trás-os-Montes and Alto Douro in Portugal, supervised by Chalmers, recreated a Roman-style lucerna and measured the properties of its light. They then used rendering software to model how the room would look when lit by such lamps (ACM Journal on Computing and Cultural Heritage, DOI: 10.1145/1551676.1551679).
The result is a warm, sumptuous glow, which the researchers describe as subtle and pleasant compared with the "rough, almost unnatural" effect of modern lighting (see images). As well as giving us more authentic images, the technique could help answer questions such as how many lamps it would have taken to light a room.
This could answer questions such as how many lamps it would have taken to light a room
Chalmers has tested the approach at other archaeological sites, with intriguing results. Simulations from Cap Blanc, a 15,000-year-old cave site in France, hint that the prehistoric inhabitants who carved wild beasts into the cave wall may have deliberately left the legs blurred to enhance the effect of movement in the light of a flickering flame.
Archaeologist Duncan Brown of the Art and Heritage department of Southampton City Council in the UK, who has worked with Chalmers, says the approach adds a new dimension to his work. "It gives you a better understanding," he says. "You can model any space you want, but unless you model the light authentically, you won't see it the same way as the people who lived there."