Several thousand incised graffiti adorn the sandstone walls of the Great Enclosure at Musawwarat es Sufra (Sudan), a unique sacral building complex dating to the Meroitic period (c. 270BC-AD350) of the Kingdom of Kush.
The often finely incised informal inscriptions and images – rare evidence of non-official art and ritual practice – are threatened by accelerated weathering and the negative side effects of increased tourism. Several past attempts at documenting the hitherto unpublished graffiti corpus have been hampered by limitations inherent in traditional photographic and other graphic recording techniques. In 2009 white light scanning was tested on some graffiti with good results, but its high cost and the loss of important colour information limited its application.
In 2011 low-cost Reflectance Transformation Imaging (RTI), which captures surface details in different lighting conditions, was tested on a large sample of graffiti. RTI is based on traditional raking light photography, where multiple images are taken from a fixed camera position using a light source that is moved between exposures. Results of the recording exercise are extremely encouraging although the outdoor field conditions posed various challenges, such as the restriction of the ideal hemispherical movement of the light source (i.e. the flash) due to walls or the ground as well as the sheer impossibility to prevent camera movement due to strong gusts of wind. Nevertheless, several hundred graffiti were captured and processed during the past field season, contributing to the virtual preservation of the graffiti corpus.
The processed RTI images can be viewed using open source viewer-software, which offers various visualisation tools. These display even finest graffiti detail that can be studied under different lighting conditions and surface rendering modes. It is planned to make the processed RTI images available for study via the open access Musawwarat Graffiti Archive.