Reflectance Transformation Imaging

Conservators, archaeologists, and conservation scientists use many pieces of equipment and methods of investigation to perform analysis of records, artifacts, and historical buildings. Analysis is performed to research materials, collect historical information, and determine how they can be preserved.

Outdoor sculptures, historic buildings, and even gravestones are severely affected over time due to the harsh environmental conditions that they must withstand. In order to work towards the preservation and documentation of these historical resources, researchers sometimes collect data on their surface, shape, and colour using Reflectance Transformation Imaging (RTI), also called Polynomial Texture Mapping. This type of analysis uses a computational photographic method that collects information on the surface through the use of light and camera positioning. It has proved particularly beneficial when decoding worn gravestones, friezes, hieroglyphics, and even faded manuscripts.

How does it work?

  • Multiple photos are taken of an object with a stationary camera, under various angles of light. The angles of light are knowns, and are required to collect the necessary images that will be used to create the final image.
  • Data produced by each image is interpreted by the RTI viewing software, then a mathematical model of the surface is created, which allows users of the software to manipulate an illumination feature to view the surface under various light angles.

 A similar method of photographic capture that is used for RTI can also be used for 3-D scanning. 3-D scanning is a popular method of collecting data of an object prior to creating reproductions or creating a digital manifestation.

 

References

Cultural Heritage Imaging. Reflectance Transformation Imaging (RTI). Retrieved from http://culturalheritageimaging.org/Technologies/RTI/.

Smithsonian Museum Conservation Institute. Reflectance Transformation Imaging (RTI). Retrieved from http://si.edu/MCIImagingStudio/RTI.

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