For photographing selected areas of Bible folios, Lundberg and Zuckerman used an imaging technique called Reflectance Transformation Imaging (RTI). It is a relatively simple photographic concept made possible by highly sophisticated computer software. An RTI image is composed of dozens of individual photographs of the same object, each with the lighting coming from a different horizontal and vertical angle. The object itself is never moved; only the lighting angle changes.
To capture images with the different lighting angles, the team at the University of Southern California has constructed dome-like structures containing lights at different positions. This apparatus isn’t very portable, so for offsite photography, simpler tools are used: a shiny ball and a length of string. One end of the string is attached to a small handheld portable electronic flash unit. The other end is positioned at the center of the subject prior to the photograph being made. This measuring string ensures a fixed light-to-subject distance, keeping the exposures consistent. The flash is positioned at a variety of horizontal and vertical angles and the successive photographs are taken. The small reflective ball is placed in the periphery of each shot—the position of the reflection of the flash unit on this sphere tells the image processing software what the X and Y lighting coordinates are for each image.
After the individual photos are created (in this case, 36 photos are taken), they are combined using specialized software into a Polynomial Texture Map (PTM), a type of image file that contains information about the appearance of each pixel in the image based on all of the horizontal and vertical lighting angles employed.
The result is an image that, when viewed with a special software application, is “adjustable” in terms of lighting angle. The viewer can choose the lighting angle with the computer mouse, and the appearance of the image will change in real time to represent the object as lit from the chosen angle. This “virtual light” can be moved around the image to see an infinite variety of views. This technology allows closer examination than was ever thought possible, revealing the tiniest of details. In using RTI, Lundberg and the Zuckermans will be able to study the dimensionality of the ink strokes made in The Saint John's Bible. Their findings can then be confirmed by the actual scribes who worked on the Bible passages photographed. This will in turn provide factual “feedback” on the interpretation of RTI imagery and strengthen the capabilities of RTI as a research tool.
Marilyn Lundberg is driven by a passion for research; she strives to be able to “read” a document in the most thorough manner possible. Ken Zuckerman’s devotion lies in discovery, preservation and distribution. Together their philosophy combines an expert knowledge of ancient texts with expertise in applying advanced technology and promoting accessibility. To this end an online database, InscriptiFact delivers high-resolution RTI images to scholars in 41 countries at no cost.
West Semitic Research Project at the University of Southern California
Left: Working in HMML's imaging studio, Marilyn Lundberg prepares to photograph a section of a Bible page. Ken Zuckerman checks the images as they are sent to the computer.
Left: Ken Zuckerman uses a length of string as a measuring tool to ensure that the light is at the same distance from the subject for all 36 photographs. This ensures consistent exposures on all the shots when they are combined to create the Polynomial Texture Map.