Cultural Heritage Imaging


Illumination of Material Culture: A Symposium on Computational Photography and Reflectance Transformation Imaging (RTI) at The Met, March 7-8, 2017 by chicaseyc

Our guest blogger, Emily B. Frank, is currently pursuing a Joint MS in Conservation of Historic and Artistic Works and MA in History of Art at New York University, Institute of Fine Arts. Thank you, Emily!

With the National Endowment for the Humanities (NEH) back on the chopping block in the most recent federal budget proposal, I feel particularly privileged to have taken part in the NEH-funded symposium, Illumination of Material Culture, earlier this month.

Co-hosted by The Metropolitan Museum of Art and Cultural Heritage Imaging (CHI), the symposium brought together conservators, curators, archaeologists, imaging specialists, cultural heritage and museum photographers, and the gamut of engineers to discuss and debate uses, innovations, and limitations of computational imaging tools. This interdisciplinary audience fostered an environment for collaboration and progress, and a few themes emerged.

The sold-out crowd at the symposium at The Met

The sold-out crowd at the symposium at The Met

(1) The emphasis among practitioners seems to have shifted from isolated techniques to integrating a range of data types.

E. Keats Webb, Digital Imaging Specialist at the Smithsonian’s Museum Conservation Institute, presented “Practical Applications for Integrating Spectral and 3D Imaging,” the focus of which was capturing and processing broadband 3D data. Holly Rushmeier, Professor of Computer Science at Yale University, gave a talk entitled “Analyzing and Sharing Heterogeneous Data for Cultural Heritage Sites and Objects,” which focused on CHER-Ob, an open source platform developed at Yale to enhance the analysis, integration, and sharing of textual, 2D, 3D, and scientific data. CHI’s Mark Mudge presented a technique for the integrated capture of RTI and photogrammetric data. The theme of integration propagated through the panelists’ presentations and the lightning talks, including but not limited to presentations by Kathryn Piquette, Senior Research Consultant and Imaging Specialist at University College London, on the integration of broadband multispectral and RTI data; Nathan Matsuda, PhD Candidate and National Science Foundation Graduate Fellow at Northwestern University, on work at NU-ACCESS with photometric stereo and photogrammetry; as well as a lightning talk by Chantal Stein, in collaboration with Sebastian Heath, Professor of Digital Humanities at the Institute for the Study of the Ancient World; and myself, about the integration of photogrammetry, RTI, and multiband data into a single, interactive file in Blender, a free, open source 3D graphics and animation software.

(2) There is an emerging emphasis on big data and the possibilities of machine learning.

Paul Messier, art conservator and head of the Lens Media Lab at the Institute for the Preservation of Cultural Heritage, Yale University

Paul Messier, art conservator and head of the Lens Media Lab at the Institute for the Preservation of Cultural Heritage, Yale University

The notion of machine learning and the possibilities it might unlock were addressed in multiple presentations, perhaps most notably in the “RTI: Beyond Relighting,” a panel discussion moderated by Paul Messier, Head of the Lens Media Lab, Institute for the Preservation of Cultural Heritage (IPCH), Yale University. Dale Kronkright presented work in progress at the Georgia O’Keeffe Museum in collaboration with NU-ACCESS that utilizes algorithms to track change to the surfaces of paintings, focusing on the dimensional change of metal soaps. Paul Messier briefly described the work being done at Yale to explore the possibilities for machine learning to work iteratively with connoisseurs to push data-driven research forward.

Mark Mudge, President of Cultural Heritage Imaging, leads a panel discussion

Mark Mudge, President of CHI, participates in a panel discussion

(3) The development of open tools for sharing and presenting computational data via the web and social media is catching up.

Graeme Earl, Director of Enterprise and Impact (Humanities) and Professor of Digital Humanities at the University of Southampton, UK, gave a keynote entitled “Open Scholarship, RTI-style: Museological and Archaeological Potential of Open Tools, Training, and Data,” which kicked off the discussion about open tools and where the future is heading. Szymon Rusinkiewicz, Professor of Computer Science at Princeton University, presented “Modeling the Past for Scholars and the Public,” a case study of a cross-listed Archaeology-Computer Science course given at Princeton in which students generated teaching tools and web content that provided curatorial narrative for visitors to the museum. CHI’s Carla Schroer presented new tools for collecting and managing metadata for computational photography. Roberto Scopigno, Research Director of the Visual Computing Lab, Consiglio Nazionale delle Richerche (CNR), Istituto di Scienza e Tecnologie dell’Informazione (ISTI), Pisa, Italy, delivered the keynote on the second day of the symposium about 3DHOP, a new web presentation and collaboration tools for computational data.

We had the privilege of hearing from Tom Malzbender, without whose work at HP Labs in the early 2000s this symposium would never have happened.

The keynotes at the symposium were streamed through The Met’s Facebook page. The other talks were recorded and will be available in three to four weeks. Enjoy!

Tom Malzbender, the inventor of RTI, at the podium

Tom Malzbender, the inventor of RTI, at the podium

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Reflections on Threats to World History by chicaseyc

Our guest blogger, Matt Hinson, is a junior at the School of Foreign Service at Georgetown University in Washington, D.C. He spent the summer as an intern at CHI. Thanks, Matt!

ISIS destruction at Nimrud

Screen shot from ISIS video of the destruction of Nimrud, April 2015

During my summer internship at Cultural Heritage Imaging (CHI), I learned a great deal about the danger facing many of the world’s treasures as well as the efforts to save them. My background in international history leads me to believe that international law and policy can help to address many of the dangers. I have also learned how CHI is contributing to the revolution in how we interact with information and deal with these cultural heritage threats.

The variety of projects that CHI undertakes demonstrates the wide range of threats facing cultural heritage. Although some of CHI’s most recent projects have dealt with weathering and natural deterioration, it is important to understand the other risks to humanity’s greatest treasures. One can categorize tangible cultural heritage sites into natural formations, historic structures, including cities and sculptures, and inscriptions. Complex rock formations, the cities built by ancient cultures, works of art, and monuments are all included. It is also important to recognize cultural heritage sites that hold symbolic value to a specific community or group. Many of these are protected by national parks and museums, but only to a certain extent. Multiple forces continue to threaten this material.

Threats can be divided into man-made and natural. The man-made category encompasses destruction from conflict, construction, and development. Human neglect can also be included as a potential danger to the survival of important sites. War has become one of the most widely observed man-made threats to cultural heritage, particularly in ongoing conflicts in Africa and the Middle East. Groups fighting for ideological reasons, such as religious fundamentalists, have attempted to destroy artifacts that contradict their beliefs. The recent destruction of the ancient city of Nimrud by the Islamic State is one prominent example. Conflict areas tend to encourage looting of historic sites, leading to sales of antiquities on the black market. Often the lure of financial gain from the development of sites that contain important heritage outweighs the cultural value that is at risk. One example is the impending destruction of an ancient Turkish cave city after the completion of a dam that will put it under water.

In most parts of the world, environmental threats to cultural heritage are more prevalent than man-made ones. For monuments, statues, and other structures made of stone, weathering is a common means of loss. Precipitation, especially acid rain, and other kinds of exposure to water can lead to the gradual erosion of stone, rotting of wood, and general deterioration of sites and monuments.

map-of-threats-from-sea-rise

National Park Service (NPS) map of the 105 US parks vulnerable to sea level rise. From “Strategies for Coastal Park Adaptation to Climate Change”: http://marineprotectedareas.noaa.gov/pdf/helpful-resources/webinar_beavers_schupp_nps_coastalcasestudies_111413.pdf

Environmental damage caused by climate change is accelerating the destruction. Rising sea levels are predicted to have a particularly devastating impact on many cultural sites. A recent study shows that predicted sea level rise over the next years will put 80% of Icelandic cultural sites at risk. According to the National Park Service (NPS), natural heritage sites in the US are also at risk. The NPS reports 105 parks as “vulnerable to sea level rise.” The effect on weather patterns due to climate change, particularly the increase in severe weather events, could pose major threats to cultural heritage sites beyond normal historical weathering.

How can these various threats be addressed? Archaeological preservation is one common method of physically excavating and preserving important historical artifacts. Moving objects to museums has successfully preserved different forms of cultural heritage throughout time. Digital imaging, practiced here at CHI, is a powerful tool to be used alongside archaeological methods to provide additional, more detailed information for the historical record. Digital representations of cultural heritage sites can be used to monitor the rates of change at these sites as well as preserve their shape and cultural significance. The re-creation of cultural heritage with digital methods also impacts how information is shared: an artifact that may be thousands of miles away can be viewed by anyone anywhere in an accurate digital form. This also allows objects and sites to stay in their original locations while providing access to their digital representations.

From my perspective, a crucial element in furthering the protection of cultural heritage is the legal and political protection of these sites. International law has developed to protect the things that have been identified as most sacred to communities around the world, including human dignity, life, and freedoms. Cultural heritage must be worthy of the same kind of protection every day as well as in wartime. Although some institutions already exist to defend cultural heritage, UNESCO, for example, I believe we must govern the protection of artifacts and sites with laws just as we do in cases of war crimes and sovereignty.

Another lesson I take away from my time at CHI concerns the changes in our interactions with information and knowledge. I am familiar with the usual media in our repositories of knowledge: text, photographs, video, and audio. While these media convey interpretations and descriptions of their subject matter, they rarely can stand as accurate representations of sites and objects. The potential that three-dimensional imaging brings to human interaction with information can be enormous. Many historical and cultural wonders previously limited to a particular geographical area could be made accessible to others, leading to progress in historical and interpretive research. Expanding research on these 3D methods, such as the ongoing work at CHI, can lead to highly effective ways of contributing to this revolution in information.

RTI study of the Sennedjem Lintel

The Sennedjem Lintel from the Phoebe A. Hearst Museum of Anthropology at the University of California, Berkeley. Lower left left shows the surface color and shape. Upper right shows an enhanced surface shape.

CHI has exposed me to a lot of these problems facing world heritage sites but has also introduced me to the preservation and information successes that are possible with different methods and technologies.



Behind the Scenes: Museum Photography at the Oriental Institute by marlinlum

Recently Anna R. Ressman, Head of Photography at the Oriental Institute Museum, University of Chicago, shared a compelling article with me, and now I’m sharing it with you.

Here is a link to the Oriental Institute newsletter (PDF), which contains the article entitled, “Behind the Scenes: Museum Photography at the Oriental Institute.

Anna describes the process in which five very different artifacts are documented, each with a unique challenge. And yes, you guessed it, one of those artifacts was documented using the RTI highlight method.

Documentation of the Egyptian stele “was photographed with a method of computational photography called Reflectance Transformation Imaging (RTI).”

Using RTI to photograph OIM E14655 with photo assistants K. Bryce Lowry and Austin M. Kramer

Using RTI to photograph OIM E14655 with photo assistants K. Bryce Lowry and Austin M. Kramer

OIM E14655, Egyptian Stele, Limestone, New Kingdom, Medinet Habu, Egypt. 36x26cm

OIM E14655, Egyptian Stele, Limestone, New Kingdom, Medinet Habu, Egypt. 36x26cm

Specular enhancement using RTI of Egyptian Stele OIM E14655

Specular enhancement using RTI of Egyptian Stele OIM E14655

Anna concludes the section on RTI with these insights: “RTI files can be created in such a manner that pixel data is analyzed to show specular information rather than color data, which can reveal more information about the surface of the object than color data alone (figs. 3–4). As you can see, the inscriptions on the stele are much clearer in the specular-enhancement PTM image (fig. 3), even though the studio photograph (fig. 4) was taken using a macro lens under controlled studio lighting. The former may not be as aesthetically pleasing as the latter, but it reveals much more information than would normally be seen — and that is just a single image out of a series of forty-five.”

Be sure to download the complete article and check out the rest of the newsletter as well.

Anna R. Ressman is Head of Photography at the Oriental Institute Museum, University of Chicago, USA. Anna is also a freelance photographer and a fine artist.

[Photos by Anna R. Ressman/Courtesy Oriental Institute Museum, University of Chicago]



Interview: James Coddington, Chief Conservator, Museum of Modern Art, New York by cwillen

CHI Executive Director Debra Dooley recently conducted an email interview with James (Jim) Coddington (JC), Chief Conservator at the Museum of Modern Art (MoMA) in New York. CHI is building a custom light array for MoMA’a Conservation Department to help with capturing reflectance transformation imaging (RTI) media of objects in the museum’s collection.

1. How long have you been at the MoMA?

JC: 23 years

2. As Chief Conservator at MoMA, are you constantly searching for new techniques to preserve and restore art?

JC: It is a necessity when conserving contemporary art in particular.

3. What are you doing to digitally document, analyze, and preserve the MoMA collection at present?

JC: We are using standard RGB imaging as well as multi-spectral imaging via a spectral estimation technique using a standard RGB camera with filters. We also maintain written digital documentation of treatments and other reporting.

4. Why have you decided to expand from what you are doing now into reflectance transformation imaging (RTI) techniques?

JC: The importance of 3D information in documenting works of art has been long recognized, mostly in the form of raking light photos. RTI gives us the means to collect substantially more 3D information in a standardized way that also provides data for scientific analysis of surface structure and topography.

4. Why did RTI interest you?

JC: I think mostly the demonstrated ease of use.

5. How will you use RTI?

JC: We will be using it initially to document texture on printed out photo papers but we expect to use it on many different types of objects in our collection.

6. A custom light array is being built for the MoMA. What objects will you capture first?

JC: See Answer #5.



Capturing Reflectance Transformation Images by cdschroer
September 30, 2009, 1:52 am
Filed under: Technology, Training | Tags: , ,

By Debra Dooley, Executive Director, and Marlin Lum, Imaging Director, CHI

We have quite a bit of information on Reflectance Transformation Imaging (RTI) on our website. But what’s the process used to create a RTI? There will be several blog entries on the process. For more detailed information we recommend that you sign up for the Digital Imaging Techniques for Conservation & Education 3-hour workshop. Check out a Flickr photostream of one of the workshops.

There are four different parts to the process: Preparation, Capture, Processing, and Viewing. This blog entry is a high-level summary of the Capture process.

There are two different methods used to capture RTI. One is called Highlight RTI and the other uses a hardware system. CHI calls the custom hardware systems we build “RTI Capture Hardware Systems” and they are usually built for specific types of objects.

Highlight RTI

The highlight method is easy to use in the field as well as in a controlled setting. You use a tripod, digital camera, a light source (strobes or continuous lighting) and other generally available equipment. That’s one of the big pluses about highlight RTI —  “over the counter,” pro-sumer photographic equipment will yield professional, museum-quality,  high-grade digital RTI surrogates.

This picture was taken after one of the workshops. This is a classic “camera down” or “floor setup,” and is pretty basic. Basics include: a tripod with the camera mounted in the down position, a wireless trigger set (pocket wizards), a 580EXII flash strobe (with a string attached), and a priceless stone tool (insert your artwork here) in the field of view.

Carefully placed next to the object are two round black shiny reflective spheres. When the strobe hits the shiny surface, it produces a “highlight.” Bling! Bling! Software used in processing the images finds the highlights in each image to derive a light position (LP).

Also in this image is a Canon EOS Digital Rebel, tethered to a laptop and being controlled by the Canon EOS utility software. The blue tape minimizes movements and vibration during the capture process. The sandbag hanging from the ball head also dampens the wiggles. Again, though basic, the results are high tech.

Highlight RTI setup

Highlight RTI setup

RTI Capture Hardware System

The RTI Capture Hardware System is better suited to controlled settings such as in a museum conservation photo/lab. One benefit of using a rig is efficiency.  Think mass production, or in this case, mass-documentation. A RTI rig/dome is extremely favorable if one needs to document a large quantity of similar sized objects: coins, signatures, stone tools, paper samples, paintings, objects, etc. etc.

The most noticeable feature of an RTI Capture Hardware system is the light array — many lights (up to 40) mounted at different angles, all directed toward the center, at the object. And of course the camera is also mounted at the apex of the unit. A PC laptop controls the light sequence and asks the camera to open the shutter when a lamp is on, capturing the image with different light positions.

This capture sequence is  managed by open source software that we teach you how to use in our workshops, so you should look into it if this is interesting to you.

4-Day Training: Reflectance Transformation Imaging:
“Generating Digital Representations of Cultural Heritage Objects”

The following image is of a custom RTI Capture Hardware System built as part of the Developing Advanced Technologies for the Imaging of Cultural Heritage Objects project. CHI built 2 identical systems, one for the University of Southern California’s West Semitic Research Project and one for CHI.

Custom RTI Capture Hardware System

Processing the Images. After capture comes the processing of your images. Stay tuned for an update on that soon.



CHI’s National Park Service Workshop by cdschroer

By Carla Schroer

The National Park Service’s National Center For Preservation Technology and Training (NCPTT) workshop was a great opportunity for the instructors as well as the participants. First, Mark and I got to spend a couple of days with Tom Noble and Neffra Matthews (from the Bureau of Land Management) prior to the workshop.

Tom and Neffra are extremely knowledgeable photogrammetry experts with lots of field experience. They also keep up with what’s going on in that field in terms of new products, and new features in existing products. They are a tremendous resource, and happy to share their knowledge. CHI welcomes any future opportunities to work with them again.

The next opportunity for me as an instructor was to hear from folks that participated about their own experiences in the field. A few had tried reflectance transformation imaging (RTI), others photogrammetry, others laser scanning, and all had done photographs and drawings (or been part of projects that did that).

The workshop afforded opportunities to discuss practical issues in the field, as well as get an understanding of some of the challenges people face, and what they are willing to do to overcome the challenges. The group worked well together, shared ideas readily, and asked good questions. I think we all got a lot out of the interaction. It wasn’t just instructors passing knowledge to students, and I really appreciated that aspect of it.

It was also fantastic that we had a range of people with a wide variety of  experiences participating. Having Professor James Davis from the University of California, Santa Cruz attend the full workshop was really valuable, because he could hear directly the issues people face, and share his perspectives as a computer scientist.

James has worked with RTI for some years, and is also well versed in a range of computer graphics techniques, including laser scanning, structured light scanning, and other forms of capturing 3D geometry. He was really interested in the challenges in the field, and what takes the most time and is the most painful about the capture process, always thinking about ways he might be able to remove some of the time consuming parts.

Overall the experience was lively, interactive, open, and fun, but we made serious progress, too. I think it added a lot to have folks staying at the Presidio and getting to know each other in the evenings. Several people mentioned how the opportunity for them was in not only getting access to the technical information, but interacting with other participants.

I think that no matter how good we get at training people with web- based materials, there will always be a place for human interaction and sharing. It was a rich experience, and I truly thank everyone involved for participating fully.

NCPTT-Workshop-Grp-Photo



Wanted: Heritage Heroes by cwillen

The United Nations Environment Programme (UNEP) declares World Environment Day each June, making this month a time to focus on how we can improve our environment and our planet.

Our global cultural heritage is a vital element of our environment. Like our natural and physical world, heritage sites and artifacts have been adversely affected by climate change and other negative environmental effects, many caused by human activities.

UNEP has created the Champions of the Earth Laureates Program to recognize the extraordinary efforts made by dedicated researchers and activists to increase environmental protection and awareness.

CHI has been inspired by the UNEP program to create a Heritage Heroes initiative that appreciates people in the heritage community who have advanced the field in so many ways. UNEP recognition categories include science and innovation, policy, inspiration and action, and entrepreneurial vision.

The CHI team can think of numerous cultural heritage workers who deserve recognition in each of these areas and in other categories, too.

However, for our first nominee, we have selected someone who has really led the way in promoting digital techniques to document and preserve cultural heritage.

Tom Malzbender, senior research scientist at Hewlett Packard Labs, has helped the field of digital cultural heritage by developing, refining, and sharing  advanced imaging techniques and other processes to digitally document and preserve artifacts.

Listen to him describe interactive relighting in a post on this blog. We hope you agree that he is a heritage hero! Let us know about your heritage heroes by posting comments in our blog.

We are interested in all kinds of heroes — not only those who excel in technology, but also those who inspire others to action — historic preservation advocates, fieldwork fiends, educators, and those working in other relevant fields.