Imaging the topography of illuminations and bookbindings with reflectance transformation imaging

Watteeuw L., Vandermeulen B., Van der Stock J., Truyen F., Proesmans M., Van Gool L., Gradmann S., ''Imaging the topography of illuminations and bookbindings with reflectance transformation imaging'', ICOM-CC’s 17th triennial conference. Building strong culture through conservation, September 15-19, 2014, Melbourne, Australia.The RICH project (Reflectance Imaging for Cultural Heritage, KU Leuven) is developing a digital imaging tool for researching, studying, and exploring the material characteristics of graphic materials. With this imaging device, the visualization of the topography of medieval book illumination and bookbinding stamps can be monitored. The research project is surveying the possibilities of using the dome-imaging system to detect damage, the effects of old and recent restorations, and conservation treatments on medieval illuminated manuscripts and their bindings. The digital imaging device digitizes with omni-multidirectional lighting and exports the results to 2-D+ and 3-D. The technique is based on polynomial texture mapping, also known as reflectance transformation imaging (RTI), an imaging technique which interactively displays objects under varying lighting conditions to reveal surface phenomena. The module is a hemispherical structure with a single downward-facing video camera (28 million pixels) that can be mounted on a book conservation copy stand to secure manipulation during imaging. The RICH hardware is modular and can be transported to the research collections. The object to be captured is placed in the center and illuminated via computer-controllable lighting using multiple white LEDs. The different angles that illuminate the surface of the artifacts reveal extreme details. For each artifact, an image is taken by the overhead camera (a total of 260 images for each object). Filters in the visualization system are incorporated into the software. Fine details can be highlighted and measured up to 10 microns, bringing out structures that would not be visible under single illumination (with shade, contrast, sharpening, and sketch filters).status: publishe