Reflectance Transformation Imaging Systems for Ancient Documentary Artefacts

Abstract

This paper discusses the interim results of the AHRC RTISAD project. The project has developed and tested a range of techniques for gathering and processing reflectance transformation imaging (RTI) data. It has also assembled a detailed understanding of the breadth of RTI practice. Over the past decade the range of applications and algorithms in the broad domain of RTI has increased markedly, with current working addressing issues such as large resolution capture, 3D RTI, annotation, enhancement amongst others. Capture of RTI datasets has begun to occur in all aspects of cultural heritage and elsewhere. This has in turn prompted the development of policies and methods for managing and integrating the large quantities of data produced. The paper describes these techniques and issues in the context of a range of artefacts, including painted Roman and Neolithic surfaces, examples of ancient documents in a variety of forms, and archaeological datasets from Herculaneum, Çatalhöyük, Abydos and elsewhere. The paper also identifies ongoing software development work of value to the broad EVA community and proposes further enhancements.

Goldfuß was right: Soft part preservation in the Late Jurassic pterosaur Scaphognathus crassirostris revealed by reflectance transformation imaging (RTI) and UV light and the auspicious beginnings of paleo-art

“…Several archaeological studies successfully applied RTI/PTM over the last years (e.g., Earl et al, 2011;Piquette, 2011;Kotoula, 2012;Duffy et al, 2013). Compared to archaeological studies, RTI/PTM imaging is rather scarce in paleontology, and only .ptm files have been used so far (Hammer et al, 2002;Hammer and Scopova, 2013) but not .rti files.…”

‘Tombstones’ in the North Italian Iron Age: Careless writers or athletic readers?

“…Thus the writer would have been able to write horizontally at all times, whatever the position or direction of the line in the final monument. Whether this was in fact the case could perhaps be elucidated by detailed study of the surfaces of the stones using a technique such as RTI (Reflection Transformation Imaging: see Earl et al 2011; Piquette forthcoming; see also Piquette and Whitehouse, Figure 1, this volume), which could show up tool marks, and indicate direction, angle and depth of carving; however, no such work has been undertaken on the Italian monuments and this remains a project for the future. Most of the stones used for the monuments -limestone, sandstone and trachyte -are relatively soft and easy to carve, the exception being the porphyry of the ciottoloni, which is a hard volcanic rock.…”

New RTI Technology for Palæography

“…The visibility of a scratch on the wood surface is enhanced under light cast at a raking angle perpendicular to the direction of the scratch. Digital photography with a series of directional light sources, with processing by the well-established methods of Polynomial Texture Mapping (PTM) and Reflectance Transformation Imaging (RTI), enables interactive visualisation of each tablet under a movable virtual light source, and facilitates their reading (Earl et al 2011).…”