Applications of Reflectance Transformation Imaging (RTI) to the study of bone surface modifications

Abstract

This article examines the application of Reflectance Transformation Imaging to the study of archaeological bone specimens. Visible surface modifications on ancient bone offer evidence of the human behaviors and natural taphonomic processes involved in artifact histories and site formation processes. Reflectance Transformation Imaging allows a researcher to record and represent an object from multiple light angles, as well as to manipulate its color and reflectance properties. Subtle bone surface details, including cut marks, striations, etching and polishing, are highlighted by this technique. Reflectance Transformation Imaging is a highly mobile process that can be completed at archaeological field sites, as well as a relatively inexpensive technique requiring only standard digital photography equipment and software that is freely available (for non-commercial use). Finally, the end result produces a digital image that can be shared with and manipulated by other researchers in order to better evaluate hypotheses and conclusions. Although the technique is limited by the degree of magnification that can be achieved using standard camera lenses and equipment, it offers a useful means of identifying specimens that require more detailed analysis or higher resolution imaging, particularly in cases where export of cultural materials is restricted or prohibited. Using a collection of worked bone artifacts from the ancient Maya site of El Zotz, Guatemala as a case study, this paper presents Reflectance Transformation Imaging as a viable tool in the analysis of worked bone production technologies and use-wear, as well as post-depositional processes and conditions.