Crafting and Visualizing Models: Photogrammetry at Bryn Mawr – by Danielle Smotherman Bennett

Cover of the Training Manual

On June 6th-9th, Mark Mudge (President), Carla Schroer (Founder and Director), and Marlin Lum, (Imaging Director) of Cultural Heritage Imaging (CHI) visited Bryn Mawr College and trained interested recent alumnae, students, faculty, and staff in Photogrammetry for Scientific Documentation of Cultural Heritage through a four-day workshop.  Mark, Carla, and Marlin were a wonderful and welcoming team that made photogrammetry very understandable and accessible to a group with a widely disparate set of skills. CHI is same group responsible for the creation of Reflectance Transformation Imaging (RTI), a type of computational photography utilizing a movable light source on an unmoving surface with a static camera position that was introduced to the study of objects in Special Collections in 2014. RTI is used presently in Bryn Mawr College’s collections and in many other institutions world-wide. CHI’s training and standards for photogrammetry are another important effort of this group for creating practical methods for digital imaging and preservation that will now be available at Bryn Mawr College.

Model as a mesh showing the position and angles in which photographs used in the model were taken.

For those of you who have not previously encountered photogrammetry, it is a type of computational photography, or digitally captured and processed images, that combines a series of carefully captured images to produce precise 3D surface data. While the technology has been around for awhile, photogrammetry has improved over the years through refined camera technologies and techniques, as well as through improvements in the software. The process is relatively quick, once you know what you are doing, portable, and uses standard photography equipment. All of these factors make it a very accessible technique to an archaeologist such as myself, both for fieldwork as well as for travelling to specific museums and sites in the future. The resulting models can be measured with a high degree of accuracy, even when the subject is not present or even available in the future. Objects may not be accessible to scholars for a variety of reasons, varying from being in a closed museum, located across the country or even the world, as well as for more dire reasons such as if an object has been lost, damaged, or completely destroyed.

Carla lecturing the first day of training

Trainees attending a lecture

Camera set up and Mark showing Zach Silvia, Sarah Luckey, and Del Ramers how to adjust the settings through the laptop

The trainees at this four-day workshop included individuals from collections management, librarians, digital scholarship specialists, anthropologists, and archaeologists, as well as others who joined for specific lectures. In particular, many of us were interested in the use of photogrammetry for the study of artifacts, architecture, sondages, and even bones, to create models. These scaled models can be used to measure features of these objects, to accurately record condition, to allow for more direct comparisons between scaled models of objects, as well as to serve as a digital archive for the future. As an archaeologist who studies Greek vases, objects which are spread out in museums and private collections around the world, can be sold and moved, lost, or broken, and often have limited angles in published photographs, it was very important for me to learn to create accurate models and to understand how to identify the inaccuracies I encounter in models as part of this training.

Casey Barrier getting photographs of the bottom of a vessel

The training divided into lectures and practical lessons, which consisted of both camera shoots and computer processing of the images. The practical lessons featured us breaking up into groups, so that everyone could get hands-on experience. Most of the training took place in the Carpenter Library, with excursions around campus to shoot particular objects as the subjects of our practical lessons. These objects include the two casts of reliefs and books in Carpenter Library, a plaque and marble sarcophagus in Thomas Cloisters, two vases in Special Collections, and the marble bench outside of Dalton. The diversity of subject objects provided us with experience in capturing images for photogrammetry in a variety of settings and with objects of varied scale that each required their own problem-solving.

Carla showing trainees (Caroline Vansickle, Sarah Luckey, Marianne Weldon, Zach Silvia, and Danielle Smotherman Bennett) how to adjust camera settings before a large project

Those of us who own personal Digital SLR cameras learned how to capture images for photogrammetry on our own cameras, but others used the cameras owned by CHI or Bryn Mawr College. The other equipment we used included a remote switch, remote flash(es), a monopod, a tripod, color card, scale bars, and a turntable, although not all of that was required for every shoot. For instance, at times we could use the ambient lighting, especially outdoors, but other times we needed to use flash or two in order to create an even illumination over the object surface. Similarly, we could only use the turntables occasional since a turntable is only practical for small, movable, and light-weight objects. Occasionally we used other materials, such as when we had to find make-shift back drops to cover reflective backgrounds, or use white foam board to reflect light.

Mark observing the creation of a model by one team (pictured: Matthew Jameson, Camilla MacKay, Del Ramers and Alicia Peaker)

After pre-processing the images through Adobe Bridge, we produced models through the use of Agisoft Photoscan Professional and the very capable Visual Resources computers. The resulting models and data can be shared with scholars around the world through as the models themselves through photogrammetry software, but also as 3D PDFs, which can be viewed in many PDF viewers. Thus, along with being a method of digital archiving of these objects, photogrammetry models can also provide more accessibility to collections.

Along with learning about how to capture and create accurate photogrammetry models, Mark, Carla, and Marlin also taught us about creating and sending verifiable data with our models. One aspect of this is generating a report within the photogrammetry software itself that contains information as to the camera information, number of images, camera locations, camera calibration, scale, error, and processing procedure and time. Another aspect is the importance of recording the process in a Digital Lab Notebook, which can be sent along with the data itself and the report to scholars looking at or using the model. This recording process includes not only the camera specifications, which are already included in the report, or only the subject of the project, but also who was involved, what equipment was used along with the camera, where and when the images were captured, and other possibly significant information.

Through the very capable training we received, we can now share the methodology that we have learned with others in the community. We can also apply the methodology and use the resulting photogrammetry models to our own research. Photogrammetry for scientific documentation has many implications for the future study of objects and architecture, in which Bryn Mawr College can now take part.

 

Behind the Scenes: Conservation of Artifacts at The Conservation Center of the Institute of Fine Arts, New York University

Last semester six objects from the Bryn Mawr College Art and Artifact collections were sent to The Conservation Center of the Institute of Fine Arts, New York University for conservation treatment. Over the course of the fall semester, students in the conservation program researched, cleaned, and repaired these objects. The objects were in need of varying treatments including re-treatment where old repair methods were causing new damage and repair to broken elements that were not structurally stable.

Several of the items were constructed of fragile or organic materials that had naturally begun to deteriorate or change over time, such as the fragile cotton and wool threads used in a pair of North American Ojibwe Beaded Garters.

95-01-228_GartersBT2

Before Treatment

 

Documentation indicating areas of damage.

95-01-228_GartersAT1_2

After Treatment

The deterioration of the threads was causing the garter to unravel and resulting in bead loss. The conservator reinforced the garter by weaving polyester threads into the unstable sections and reattaching the loose beads and surface cleaned the beadwork.

2004.17

Basket Interior Before Treatment

The plant fibers that were woven to create a North American Tlingit berrying basket had also become brittle and broken in several places. In addition, the basket had several older repairs that were contributing to the damage.

2004.17.1

Before Treatment Detail

2004.17.2

After Treatment Detail

 

 

 

 

 

 

BrynMawr_20041730_BT06

Before Treatment

BrynMawr_20041730_AT05_2

After Treatment

 

 

 

 

 

 

 

As the older repairs were deteriorating, distorting the shape of the basket, and visually distracting, they were removed and the basket was surface cleaned. The conservator was able to fill in the gaps and fix small splits to replace the older repairs and ensure that the basket would be more structurally sound.

2005_6_23a-d_IvoryRabbits_2015_BT_10

Before Treatment

Repairs to the fragile pieces of a small ivory sculpture depicting rabbits bringing rice dumplings to the rabbit in the moon also needed to be replaced. An older repair had left a visually distracting residue and was no longer stable. Thus, the conservator removed the older adhesive, surface cleaned the entire sculpture and reattached the rabbits and oar with a less obtrusive and more effective material.

2005_6_23a-d_IvoryRabbits_2015_AT_01

After Treatment

Several of the objects bore evidence of use and were in need of repair. The gourd and wood structure of a Japanese gourd-shaped box had cracked in several places, which caused the lacquer and gold sheet inlay decoration to flake off. These damages may be explained by use and possibly an incident resulting in impact. Animal hide glue, acrylic resins, and balsa wood were used to repair cracks and losses in the gourd and wooden structure. The conservator then used a variety of acrylic resins, copolymers, and putties to stabilize the lacquer surface.

BrynMawr_TN191_BT04

Before Treatment

BrynMawr_TN191_AT04

After Treatment

 

 

 

 

 

 

 

 

 

 

A Peruvian (possibly Ica) feathered mosaic miniature dress fragment bore evidence of its deposition circumstances. The fabric was buried alongside another fabric piece with silver medallions, and several medallions transferred during that contact. In addition, the delicate nature of the feathers that constitute the decoration of the garment also necessitated treatment. Although the silver medallions were not part of the original garment, they are important evidence of the context, history and use of the artifact. Thus they were stabilized and retained. The feathers were brushed into alignment and loose feathers were reattached.

Treatment Object 2

After Treatment

A North American Inupiaq drawstring bag made of fish skin was very brittle and fragile from age and had been flattened in storage, losing its original shape, in addition to having many, tears, and losses. The bag was carefully reshaped using gentle humidification and slowly expanding it into its original shape.  Before and during this process the bag was also surface cleaned.

55_E1_6_FishSkinBag_2015_AT_01

After Treatment

 

Fish Skin Bag Report Draft_FINAL(1)

Before Treatment

The conservator treating this bag created a time-lapse video of her repair work: (see link below)

www.viddler.com/v/b2b56d65

We wish to thank the graduate conservation students at The Conservation Center of the Institute of Fine Arts, New York University, Emily Frank, Rebecca Gridley, and Bermet Nishanova, as well as their professor, conservator Samantha Alderson, and Manager, Laboratories and Study Collection Catherine A. Lukaszewski for working on these artifacts to help preserve them for future generations.

 

Introducing RTI Photography to the Collections

The Special Collections of Bryn Mawr College holds an extensive collection of Greek pottery, both decorated and undecorated. This summer I, a PhD student at Bryn Mawr College, was granted one of the NEH internships to study vases with painted and incised inscriptions. As some of them are difficult to identify even when working closely with the objects, I , with the assistance of the Special Collections Intern, Katy Holladay, who is interested in archaeology and has a strong interest in technology, sought a way to properly document inscriptions that can be difficult to see in photographs, or even when handling/studying artifacts. Alex Brey, another graduate student at Bryn Mawr College, suggested the use of Reflectance Transformation Imaging, or RTI, which he had previously utilized on some of the coins and graciously agreed to show us the process. RTI is a technique that uses sequential photography of an object with variant locations for the light source, which are then combined using a program to produce a manipulative image. The manipulative image allows for the exploration of the surface of the image with gradient lighting, unlike traditional museum-quality images such as seen below.

P.961, Traditional photograph that does not show the partial inscription in the image (KA)

P.961, Traditional photograph that does not show the partial inscription in the image (KA)

P.961, RTI Viewer with Normal Unsharp Masking Rendering Mode

P.961, RTI Viewer with Normal Unsharp Masking Rendering Mode

The equipment was easy to access, since only a few other objects are needed to capture the images for RTI:

  1. a camera and tripod
  2. an external flash (with a very long cord)
  3. a remote for the camera
  4. a pair of black spheres; they need to be included in the image in order to show the position of the light source to the program in each photograph
  5. a color card needs to be included in the first image.

The software to find and view the RTI images is provided by Cultural Heritage Imaging, free of charge: http://culturalheritageimaging.org/Technologies/RTI/

We began with flatter objects, small sherds that were more similar to the coins Alex had previously done and that did not have curved surfaces, which required more practice with the lighting. It turns out that the process was relatively easy: the camera and objects remain stationary with a sphere on either side. For standing objects, the spheres are raised up, such as on pencils in the photograph below; for flat objects laying down, the spheres can be resting. The spheres should be around 250 pixels in the final photos, so the sphere size will vary with the object and zoom. The flash is moved into different positions over and around the object in a dome while the object and the camera remain unmoved; others doing RTI have created actual dome structures as guides, but that was not necessary for our initial goals.

One person can do the process alone, but a second person is very helpful. We took between 50 and 120 pictures per object, depending on the size. Katy and I did run into some problems as we began the process, including the spheres originally being too small to accurately show the location of the light source in each image for the program. After becoming more familiar with the process, we captured images of complete vases; their size and the curving surfaces presented challenges as these objects reflect he light differently. At this point, we needed to be creative for mounting the spheres – eventually using the ball bearings, magnets, and foam to create mounts for the spheres with the assistance of Marianne Weldon, the Collections Manager of the Art and Artifact Collections, but originally using pencils as stands.

Danielle Smotherman and Katy Holladay taking RTI photography of L.P.8

Danielle Smotherman and Katy Holladay taking RTI photography of L.P.8

A composite image of all of the angles of light source locations on a sphere for L.P.8

A composite image of the light source for L.P.8

The RTI Builder program cannot handle spaces in any file names. It requires specific formats for the files, which initially caused us a few problems as well. We imported the raw files as .jpg and .dng into specifically-named folders from Adobe Bridge, although another similar type of program can be used, and then followed the process in the RTI software; this was rather user-friendly. The RTI Viewer has nine different rendering modes to examine the object, once the file is compiled. The viewer also allows the user to zoom in on the images, which is why we took the images at higher resolutions, and to take snapshots of the image on the screen, such as the examples seen below.

painter

P.95, Bryn Mawr Painter, RTI Viewer with Default Rendering showing the full inscription

Using the RTI Viewer, various rendering modes can be used to explore the surface of the object, including raking light at various angles. Details can be highlighted, for instance the full inscription on P.95 can be read in the snapshot from the RTI Viewer seen above. The same snapshot also shows the contour lines evident around the reclining figure, his cup, and the hanging pipes case. The RTI provided much more than just a clearer look at the inscriptions on these vases: it indicated better evidence of the preparation work of the paintings, including highlighting sketch marks and contour lines, as well as demonstrating the presence of other techniques, such as added clay along the head. Katy noted the presence of finger prints on the name-piece of the Bryn Mawr painter, seen in the still photograph captured from the RTI viewer, seen below. In the right image below, the faded details of a wreath that had been painted on top of the hair of the youth are clearly shown with the RTI, although they can be difficult to see in traditional photos. RTI also allowed us to capture the sketching of a kylix on P.985, which is very difficult to make out in traditional photographs.

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P.95, Bryn Mawr Painter, RTI Viewer with Specular Enhancement Rendering Mode

P.212, Ancona Painter, RTI Viewer with Diffuse Gain Rendering Mode

P.212, Ancona Painter, RTI Viewer with Diffuse Gain Rendering Mode

P.985, unattributed, RTI Viewer with Diffuse Gain Rendering Vie w

P.985, unattributed, RTI Viewer with Diffuse Gain Rendering View

The files we created can provide better access to the objects for scholars unable to physically visit the collections and can be used as educational materials. Katy will be working with Rachel Appel, the Digital Collections Librarian, in hopes of finding a way of making the RTI images available via our online database, Triarte at http://triarte.brynmawr.edu. Also, Katy has made a short video that shows the actual RTI viewer, which can be seen at http://www.viddler.com/v/8aa9f1ac. In addition to web access, finding other platforms to present the RTI images with could be a fantastic addition to future exhibitions, inviting guests to interact with the objects as if moving them around in different lighting. Katy has produced a guide of our process for future use that goes into much more detail in the hopes that RTI will continue to be used in collections and possibly expanded to other forms of lighting, such as IR and UV, which only require the different light sources.  Overall, our experiences suggest that this is a viable and valuable process for other objects and classes of materials in the collections. I would very much like to encourage others working with objects in the collections at Bryn Mawr to make use of RTI and perhaps other collections as well. RTI is relatively easy and inexpensive process that does not require highly specialized equipment and that can greatly enhance access to the objects.

Danielle Smotherman, Doctoral Candidate in Classical and Near Eastern Archaeology

Collections Management & Practices; an AASLH Workshop Comes to Bryn Mawr College

Collections Management & Practices

July 11-12, 2013
Bryn Mawr, PA

Host: Bryn Mawr College

Cost: $270 members/$345 nonmembers; $40 discount if fee is received by June 5.

Participants will learn about their institution’s responsibility toward its collection, the necessary policies and procedures, and the best practices of collection management. During lively group discussions and hands-on activities, participants will become familiar with current issues and trends to better understand how collections fit within the context of history organizations. Participants will explore other topics including the role of collections in exhibition and interpretation, the basic steps of collections management from acquisition to disposal, professional standards and ethics, conservation on a shoe-string budget, as well as learning about the multitude of resources available for collections preservation.

Who Should Attend:
This workshop is targeted to new professionals and dedicated volunteers with responsibility for collections.

What Participants Said: “Structured well–time to get to know each other, time to interact about specific problems.” “Particularly enjoyed the participation exercise, followed by practical ideas.” “The thinking through of problems with mission statements, pest problems, and interpretation was helpful.” “I was able to see the ‘big picture’ instead of focusing on my own small concerns.”

StEps Connections:
This workshop may help institutions achieve the standards in the Mission, Vision, and Governance, Management, and Stewardship of Collections sections of AASLH’s StEPs program.

Travel Information:
Bryn Mawr College is just outside of Philadelphia. More information will be coming soon.

Instructors:

Dr. Vicki L. Berger has been a faculty member of the American Association for State and Local History for the long-running Collection Care Workshop for several years. Berger retired from North Carolina state government service in 2003. She served as Curator of Costume and Textiles and Collections Management Section Chief at the North Carolina Museum of History. During that time, she developed and taught Introduction to Museology, the beginning graduate level public history course, at North Carolina State University. Since moving to Phoenix, AZ in 2003, she has worked at the Arizona Historical Society Museum at Papago Park and the Phoenix Museum of History. In addition to her AASLH service, Berger is active in several professional organizations. She is Secretary of the International Council of Museums (ICOM) Costume Committee and travels internationally to participate in the annual meetings. A long-time board member of the Costume Society of America, Berger co-chaired the 2009 national symposium which was held in Phoenix, AZ. She also serves on the boards of the Central Arizona Museum Association, Museum Association of Arizona, and the Costume Society of America Southwest Region. She and costume colleague Sally Queen published Clothing and Textile Collections in the United States: A CSA Guide in 2006. Berger earned her bachelor’s and master’s degrees at the University of Arizona and her Ph.D. at Florida State University.

Helen Alten, is the Director of Northern States Conservation Center and its chief Objects Conservator. For nearly 30 years she has been involved in objects conservation. She completed a degree in Archaeological Conservation and Materials Science from the Institute of Archaeology at the University of London in England. She has built and run conservation laboratories in Bulgaria, Montana, Greece, Alaska and Minnesota. She has a broad understanding of three-dimensional materials and their deterioration, wrote and edited the quarterly Collections Caretaker, maintains the popular www.collectioncare.org website, was instrumental in developing a state-wide protocol for disaster response in small Minnesota museums, and is always in search of the perfect museum mannequin. She has published chapters on conservation and deterioration of archeological glass with the Materials Research Society and the York Archaeological Trust, four chapters on different mannequin construction techniques in Museum Mannequins: A Guide for Creating the Perfect Fit (2002), preservation planning, policies, forms and procedures needed for a small museum in The Minnesota Alliance of Local History Museums’ Collection Initiative Manual, and is co-editor of the penultimate book on numbering museum collections (still in process) by the Gilcrease Museum in Oklahoma. Helen Alten has been a Field Education Director, Conservator, and staff trainer. She began working with people from small, rural, and tribal museums while as the state conservator for Montana and Alaska. Helen currently conducts conservation treatments and operates a conservation center in Charleston, WV and St. Paul, MN.

Tentative Agenda:

The workshop will begin with registration at 8 a.m. on Thursday and conclude at 5 p.m. on Friday. Click here for a copy of the 2011 workshop agenda. Please note that this agenda is subject to change. A final workshop agenda and participant materials will be distributed at registration.

To register: http://www.aaslh.org/collwork.htm