Tag Archives: Reflectance Transformation Imaging

Fun with PhotoDoc: Collaborative RTI (Edition 12)

One of the exciting things about the Preservation Lab is you never know what’s going to come into the Lab next! Sure, sometimes we know a little bit ahead of time about upcoming projects, but usually the special collections intake meetings are filled with “oohh’s”, “aahh’s” and sometimes “oh no’s”. But it’s not very often that you get to work on a project, here in Cincinnati, while the objects themselves are across the Atlantic. Combine that with RTI (Reflectance Transformation Imaging), a variety of Vesalius related texts, and an opportunity to collaborate with other photographers, and you’ve got a recipe for one exciting project!

Currently in the planning stages, the Winkler Center for the History of the Health Professions will host a series of Cecil Striker lectures and a physical exhibition that will celebrate the work of Andreas Vesalius. The series and exhibition is entitled The Illustrated Human: the Impact of Andreas Vesalius and is sponsored by Stephen and Sandra Joffe. Vesalius was a renowned 16^th century author and physician, whose iconic work on human anatomy, De Humani Corporis Fabrica Libri Septem, is considered one of the most influential anatomy books ever written. Three rare first edition Vesalius volumes will be exhibited during this upcoming lecture series, gratuitously on loan from Stephen and Sandra Joffe. Dr. Joffe is a long-time UC supporter and an emeritus faculty member.

For the upcoming exhibit, the Lab will be creating custom supports, as needed, to display the volumes, and providing imaging of various pages and illustrations for promotion. I will also be doing any additional specialized imaging that might be helpful.

Since we believe that some, if not all three bindings coming to Cincinnati, might be original to the volumes, and we immediately thought of RTI and wondered if it could provide new insights to researchers. After seeing the wonders of RTI, via RTI examples from the Lab, the owners of the Vesalius editions were interested in having RTI done on a selection of Vesalius items in their collection, including some that wouldn’t be coming to the Lab. The only hitch? The volumes are at their home in Scotland. The solution: hire a local photographer, Iain McLean, to carry out the capture portion of the RTI in Scotland, and have the files shared with the Lab for processing and rendering. Though Iain is an established commercial photographer with a digital imaging background, RTI was a new adventure for him, so I shared some resources with him, including CHI’s Guide to Highlight Image Capture and some notes and resources created by the Lab during our various capture sessions. Iain and I then met via Zoom in mid- August to discuss the ins and outs of RTI highlight capture prior to his capture session on August 20^th. Iain also brought his colleague and fellow photographer, John Linton, into the fold to assist him during the capture session, which I recommended highly because though it might be possible to do RTI solo, I can’t imagine a capture session without my normal collaborator and the Lab’s Assistant Conservator, Catarina Figueirinhas. The session would take double the time and I’d make five times the mistakes without Cat! (Check out a time lapse video of Cat and I doing RTI in the Lab on our YouTube channel).

Image of Iain and John carrying out the RTI capture session in Dunderave castle. — Iain and John during the capture session, featuring one of my favorite volumes that they captured that day. (This image was taken by Iain and kindly shared with me.)

After a successful test capture session, Iain and John were ready for the main capture session on August 20^th. They ended up capturing the front and back covers of seven volumes. Once the massive capture session was completed, Iain shared the jpegs with me so that I could begin processing the images in RTI Builder and then rendering the snapshots in RTI Viewer.

This is a time lapse video of the capture session. (This video was created by Iain and kindly shared with me.)

After processing the 679 images and rendering the snapshots, here are some of my favorite finds:

This is a composite of two RTI generated images. The left shows the default mode, and the right specular enhancement. — This a side-by-side of an upper cover. The left image shows the default lighting mode in RTI Viewer and the right show the specular enhancement mode. On the right, just above the center panel, you can see the letters GFV (above the panel) and 1567 (below the panel), which are much more visible with the specular enhancement mode than under normal illumination.

This is a composite of three RTI generated images. The left is the default mode, the center is Normals Visual mode and the right is specular enhancement mode. — Here you can see a detailed composite of another cover’s center panel. On the left is the default/normal illumination mode, the center shows the normals visualization mode, and the right is the specular enhancement mode. You can see by employing the two specialized RTI modes the ornate detail of the cover is far more readable.

This is a composite of two RTI generated images, diffuse gain mode and default mode. — This composite of the upper cover features the diffuse gain mode on the upper left half, and the default lighting mode on the lower left half. The diffuse gain mode really accentuates the features of the man in the center panel.

This is a composite of two RTI generated images, default mode and specular enhancement mode. — This composite of the upper cover features the diffuse gain mode on the upper left half, and the default lighting mode on the lower left half. The diffuse gain mode really accentuates the features of the man in the center panel.

This is a composite of two RTI generated images, default mode on the left and specular enhancement mode on the right. — This composite of another upper cover shows the default mode on the left and the specular enhancement mode on the right. With this one, the discoloration of the cover distracts the eye and pulls it away from the detail of the decoration, but with the specular enhancement mode you can eliminate the color completely and modify the secularity so that your eye can focus solely on the elaborate detail.

This was such a fun experience for me, and I really enjoyed collaborating with colleagues outside the conservation field and across the pond! And I look forward to the condition photography of the three volumes and any additional specialized photography that might be helpful.

Special thank you to Stephen and Sandra Joffe for allowing their important collection items to be photographed, and for giving the Lab full permission to use the generated images. Also, a very special thanks to photographers Iain McLean and John Linton for capturing these covers and for collaborating with me on this exciting project.

Jessica Ebert [UCL] – Sr. Conservation & Photographic Documentation Specialist

Fun with PhotoDoc – RTI Viewer Video (Edition 6)

In my last “Fun with PhotoDoc” post I discussed the my recent RTI training with Cultural Heritage Imaging at Yale University. If you missed that post you can check it out here. In that post I discussed our first RTI capture session on a book entitled, Aller Bücher und Schrifften des thewren, seligen Mans Gottes Doct. Mart. Lutheri …, which is part UC’s Archives & Rare Books Library’s collection and is the eighth volume in an eight volume set. The binding is most likely age-hardened alum-tawed leather (though possibly vellum) on wooden boards with embossed paneled decoration that is barely visible under normal illumination. In that first RTI blog post I shared some snapshots of the various RTI modes you can explore within the RTI Viewer software, but I knew that I ultimately wanted to create a video capture of the RTI Viewer in action. I was finally able to do that using a free software called TinyTake.

This video can also be viewed through UCL Media Space: https://stream.libraries.uc.edu/media/AllerBucherUndSchrifften_i17632730_VideoCaptureRTI/1_s13c9opc
In this video we explore the following modes built within the RTI Viewer as the light position is moved around the object:

Default Mode (HSH)
Specular Enhancement Mode with color removed (HSH) – notice the “1571” inscription that becomes more apparent. This volume was printed in 1568, and we believe that 1571 was when the publication was bound.
Normals Visualization Mode (HSH) – allows the human eye to better determine is convex and concave on the surface of the cover.
Diffuse Gain Mode (PTM) – This mode is ideal for visualizing surface abrasions and losses. Take notice of the “ID” inscription that becomes more visible, and when we switch back to the default mode you can see that this “ID” inscription is virtually invisible to the naked eye.

I have to say, Catarina and I really enjoyed the capture process for this binding, but when we found that “ID” and then looked at the physical binding and could barely see anything…we were kind of giddy! I’m hoping to create more RTI Viewer video captures like this as we carry out more RTI capture sessions for collection materials. When I do, I will make sure to share them here.
Jessica Ebert (UCL) – Conservation Technician

Fun with PhotoDoc – RTI (Edition 5)

At the beginning of April I was lucky enough to attend a RTI (Reflectance Transformation Imaging) workshop offered by Cultural Heritage Imaging (CHI) at Yale University. CHI is a non-profit organization that shares and teaches RTI and Photogrammetry technology with cultural heritage institutions around the world. The class I attended was a 4-day NEH grant sponsored course taught by three RTI experts from CHI, and it was amazing!

This is a composite image of all the highlight points from one RTI section. The software uses these highlight points to map the surface shape and color of your object.

So, what is RTI? CHI describes it on their website as “a computational photographic method that captures a subject’s surface shape and color and enables the interactive re-lighting of the subject from any direction”. For highlight RTI, which is the least expensive and most accessible method for most institutions and what I was taught in the class, you basically take a series of 36 to 48 images of an object where everything is constant (settings and position of objects, camera and spheres) except for the light position. With a reflective black sphere (or 2) set up next to your object, you move you light source around the object at varying angles. Then, you take that set of images and plug them into the free RTI software provided by CHI and the algorithm detects the sphere(s) and the highlight points (from your light) captured on the sphere(s) and voila!…you have an fun and interactive way to look at your object’s surface texture.
Before I attended this fantastic training opportunity, our conservator and I knew right away what the subject of our first capture would be when I returned…a 16th century German Reformation text by Martin Luther with a highly decorated cover that is practically invisible under normal illumination.

Here’s a time lapse video of our first (and second) capture in the Lab…
That day (Tuesday) were were able to capture the upper and lower covers of the Reformation text (from ARB), the original silk cover from a 17th century Chinese manuscript (from Hebrew Union College) and an illuminated page from a German vellum prayer book (from PLCH). And here our some snapshots of our results from two of those captures (click on the thumbnails for a larger view of the image)…

This possibly 13th century German Prayer Book has a full stiff vellum binding and an illuminated first page. The varying modes highlight condition issues like worn/abraded parchment and flaking gold illumination, as well as the overall surface texture of the illumination.

I hope you’ve enjoyed getting a little sneak peek into RTI. I will be demoing and discussing in further depth this afternoon from 1:30 to 3pm at the Lab’s annual Preservation Week Open House. I also hope to do more RTI captures/processes in the future and share them here.
Jessica Ebert (UCL) – Conservation Technician