RTI on Katib Khosru wa Shirin (Exterior Cover)
From Jessica Ebert
This is video capture that explores highlight Reflectance Transformation Imaging (RTI) using the RTI Viewer (provided by Cultural Heritage Imaging - free downloadable software for view RTI captures). This RTI session was carried out by Catarina Figueirinhas and Jessica Ebert. To learn more about RTI visit the Lab's blog post on the subject: http://blog.thepreservationlab.org/2017/04/fun-with-photodoc-rti-edition-5/ .
This is the Katib Khosru wa Shirin, an Archives and Rare Books collection item. You can read more about this Persian love story, here. This book was previously treated by Gabrielle Fox, conservator and local fine-binder. The book is often used in classroom teaching and presentations, so it was chosen as a candidate for RTI (Reflectance Transformation Imaging). We conducted three separate highlight RTI capture sessions; one of the interior leather which features pigmented paper decoration with gilt leather decoration over top of that, one of an illustration where a significant amount of pigment was missing, and finally one of the embossed, gilt leather exterior cover (represented here in this video capture).
This video begins with in the default mode, which allows the user to move the light position around the object. Moving the light around the object at a severe 15 degree angle allows you to view the object under raking illumination. Commonly used in conservation photographic documentation, raking illumination shows off the depths and disturbances in the surfaces texture of the object, hence why it is commonly used to illustrate tears and cockled in paper. For this cover you might notice a slight deformation in the surface of the cover, especially near the center.
In the specular enhancement mode you can clearly see the intricacy of the this detailed embossing.
The normals visualization mode helps to show the dimension of the surface, allowing the view to more accurately see what is concave and what is convex.
The diffuse gain mode is ideal for identifying areas of surface abrasion and deformation, such as the large line that bisects the cover.