Michael Maggen: The illuminated pixel: Adaptation of infrared and visible light reflectance transformation imaging (RTI) in exploring a medieval illuminated manuscript

More than ten years have passed since the Polynomial Texture Mapping (PTM) photography method was first introduced by Malzbender, Gelb and Walters in Hewlett-Packard Technical Report HPL-2000-38. PTM file is a complicated mathematical model describing luminance random light direction data for each pixel in a given image. The stored information with in the pre pixel (a kind of metadata information) contains data about surface scattering, shades, inter reflections and colours, which allows virtual enhancement of a photographic image. This dynamic method of texture mapping transforms the realism of any given surface from two-dimensional representations to three-dimensional ones. RTI techniques have gained much attention in various image processing fields, and are applicable to conservation practices as well. RTI enables conservators to explore the surface in a new way and possibly to discover details invisible to the naked eye.

At present, RTI research is not limited only to real size digital photography it also extends to use with microscopy. This paper suggests to the conservation community how to build a relatively low-cost RTI installation, and it explores the surface of a 15th -century illuminated Jewish manuscript from the collection of the Jewish Art & Life Wing of the Israel Museum in Jerusalem Israel. This research compares the use of near infrared RTI with visible light RTI, and is possibly one of the pioneer studies in this area.