Reflectance Transformation Imaging (RTI)
Reflectance Transformation Imaging (RTI) uses digital luminance properties to reveal surface texture in great detail. For example, a piece of terra sigillata was found during a survey, but its stamp was unreadable to the naked eye. A sequence of fifty photos with varied angles of light were taken using a digital camera and LED flashlight. The photos were then loaded in the free RTIBuilder software and processed to create a 3D texture.
Using specular enhancement it was possible to read the stamp by setting the artificial light to a low grazing angle. The stamp belongs to Vegetus, a potter from the Po Valley dating to 30- 10 BC. His wares are mostly found in Italy, though they were traded as far as Austria and Greece.
This is an excerpt that appeared in Submerged Heritage.
A journal article by David Selmo et al. titled, “Underwater Reflectance Transformation Imaging (URTI): A new technology for in situ Underwater Cultural Heritage object level recording,” is currently under review.