Cultural Heritage Imaging


The oldest footprints outside of Africa: an interview with Dr. Sarah M. Duffy about the imaging of this incredible find by cdschroer
September 22, 2014, 9:18 pm
Filed under: Commentary, Guest Blogger, News, On Location, Technology | Tags: , ,

Sarah Duffy, PhD is a Postdoctoral Research Associate at the University of York in the Department of Archaeology. In May of 2013, after a series of storms, ancient footprints were revealed on a beach near Happisburgh (pronounced “Hays-boro”) on Britain’s east coast in Norfolk (see a 6-minute video). The footprints were fragile and washing away a little day by day. Sarah was called to the site by Dr. Nick Ashton, Curator of Palaeolithic and Mesolithic collections at the British Museum, to document it. Here is our interview with Sarah about this dramatic discovery.

Duffy-Happisburgh-BM

Sarah shooting photogrammetry in the rain. Image courtesy of Natural History Museum, London, UK

CHI: Sarah, can you tell us how you got involved in the project and what you found when you arrived?

Sarah: It really came down to good timing and an opportune meeting of research colleagues. When the footprints were discovered, I had just begun working with Dr. Beccy Scott at the British Museum on a project based in Jersey called “Ice Age Island”. Beccy and my partner, Dr. Ed Blinkhorn, another early prehistoric archaeologist, have collaborated for many years, and he introduced us. During the week of the discovery, Beccy happened to be at a research meeting with Dr. Nick Ashton and suggested that he get in touch with me about the Happisburgh finding.

The next day, I received a call from Nick who asked if I would be able to take a trip to Norfolk to record some intertidal Pleistocene deposits at Happisburgh. Having just completed my PhD thesis (a “dissertation” in US currency), I was up for an adventure and ready to take on the challenge, and so I was on a train to the southeast coast two days later.

My first plan of action was to figure out how on earth you pronounced the name of the site! The next step was to figure out what equipment I would need to have available when I arrived. This proved somewhat challenging, as I had never visited the Norfolk coast, and it seems quite humorous in hindsight that one of the pieces of kit I requested was a ladder.

All of this said, the urgency to get the site photographed became clear when I showed up one very rainy afternoon in March. Standing on the shore, I felt very privileged to have been invited to record such an important set of features, which disappeared within only weeks of their discovery by Dr. Martin Bates.

CHI: What were your goals in the project and why did you choose to shoot images for photogrammetry? Can you tell us a little bit about your approach?

Sarah: Since I wasn’t sure what to expect when I reached the site, I took both photogrammetric and RTI kit materials with me. I intended to capture the 3D geometry of the prints with photogrammetry and subtle surface relief with RTI. However, when I arrived, both the weather and tidal restrictions limited the time we were able dedicate to recording. I therefore focused my efforts on photogrammetry, which proved a flexible and robust enough technique that we were able to get the kit down the cliff side in extremely challenging conditions and capture images that were used later to generate 3D models.

Based on the looming return of the tide and the amount of time required to prepare the site, our window of access was quite small. While I took the images, aided by Craig Williams and an umbrella, the rest of the team battled the rain and tide by carefully sponging water from the base of the features. As mentioned, I originally intended to capture images from above the site using a ladder. However, as the ladder immediately sank into the wet sand, I was forced to find other means of overhead capture: namely Live View, an outstretched arm, and umbrella. There was just enough time to photograph the prints, loosely divided into two sections, using this recording approach before we had to retreat back up to the top of the cliff (and to a very warm pub for a much deserved fireside pint!).

Footprints-model-SMD

3D model of laminated surface containing the footprints at Happisburgh. Photo by Sarah M. Duffy

CHI: When you got back to your office, how long did it take you to process the images, and what software did you use?

Sarah: Originally, I used the Standard Edition of PhotoScan by Agisoft, later returning to the image set in order to reprocess it with their Professional Edition. PhotoScan’s processing workflow is relatively straightforward, and the time required to generate geometry is somewhat dependent on the hardware one has access to. The post-processing of the images was by far the most time-consuming component of the processing sequence. Since the software looks for patterns of features, there was a substantial amount of image preparation that needed to be completed first, before models could be produced. For example, rain droplets on the laminated surface that contained the prints needed to be masked out, as well as the contemporary boot prints that accumulated in the sand that surrounded the site throughout the image sequence.

CHI: How were the 3D models you produced used by the other archaeologists involved with the site?

Sarah: Once the models had been generated, the rest of the team, including Nick Ashton, Simon Lewis, Isabelle De Groote, Martin Bates, Richard Bates, Peter Hoare, Mark Lewis, Simon Parfitt, Sylvia Peglar, Craig Williams, and Chris Stringer, wrote the paper on the results. Nick Ashton and Isabelle De Groote closely analyzed the models of the prints in order to study size, movement, direction, and possible age of the early humans who might have created these features. Isabelle later worked with the 3D printing department at Liverpool John Moores University in order to have one of the digital models printed.

CHI: Since the footprints were washed away, your images are the best record of the site that exists. Are the 3D models accessible? What will you do to preserve this material?

Sarah: Coverage of the footprints, including excerpts of the digital models that I generated and the 3D printout, can be viewed at the Natural History Museum exhibit in London, Britain: One Million Years of the Human Story, which closes September 28th. Findings from the analysis have also been published in PLOS ONE, an open-access, peer-reviewed scientific journal.

As mentioned, when I visited the site last March, I had hoped to undertake a RTI survey. Although conditions on the day of recording did not permit multi-light capture, I have since been able to generate virtual RTI models that reveal the subtle topography of the prints. An excerpt of one of these models can be viewed on my website.

Additionally, the research team, in collaboration with the Institute of Ageing and Chronic Disease at Liverpool, are currently working on extracting further information from the image set. Findings from this work will be made available in the future. Once analysis is complete, the images and resulting models will be archived with the British Museum.

CHI: Thank you for your time, Sarah, and what a great story!

Sarah Duffy has been collaborating with Cultural Heritage Imaging (CHI), including taking CHI’s training in Reflectance Transformation Imaging (RTI) and working with the technique since 2007 while she was a graduate student in Historic Preservation at the University of Texas at Austin. Sarah authored a set of guidelines for English Heritage on RTI. During her doctoral work, she also began to apply her imaging skills in the area of photogrammetry.



Why a Nonprofit? The Seeds of CHI by cdschroer
July 3, 2014, 3:44 am
Filed under: Commentary, News

We often get asked why we set up CHI as a nonprofit. I can understand the question, because we are doing some pretty high-tech projects, and we work with a number of famous institutions whose names people recognize, perhaps making us seem grander and better endowed than we really are.

There are a number of reasons why a “public benefit charity” structure made sense to Mark and me when we founded CHI in 2002. The greatest impetus for it was a personal vision we shared.

Mark and Carla at entrance to Dolmen de Antales, a Megalithic tomb in Portugal.  June 2006

Mark and Carla at entrance to Dolmen de Antales, a Megalithic tomb in Portugal. June 2006

My background is in computer science, and I worked in software product development for years. At some point I had decided I wanted to apply my skills to “make the world a better place.”

Mark had similar leanings. His background was in philosophy and studio arts, primarily sculpture. He began looking into 3D modeling and laser scanning in the late ’80s, and by the mid-1990s he was teaching the subject. I had a minor in sculpture and ceramics. We both loved history, art, and archaeology. We had met in 1983 and married in 1989. By the late ‘90s, digital cameras were coming into play, and structured light scanning technology was becoming available for 3D capture.

Mark and I got fired up. We started seeking out people who worked in archaeology or museums to better understand their needs. Our first questions were: What did they wish to do that they couldn’t do in the field? Could the emerging imaging technologies help them in research and creating access to more cultural material?

Over time, and as we learned more, the seeds of CHI took root in us. By 2002 we began to imagine how existing and emerging technologies could be used to create robust, powerful, low-cost tools to document cultural heritage objects and collections. And so we formed Cultural Heritage Imaging.

Today, well over 10 years after we started our nonprofit, we remain committed to fostering the improvement, availability and adoption of these documentary tools. We see them as “democratizing technology,” because our vision is founded on making cultural and natural science techniques and materials available to people all over the world.

Many of our collaborations are only possible because we are a nonprofit. “Pulling on the same oar” for humanity’s benefit is a powerful reward. Our nonprofit status is attractive to top researchers and organizations who are drawn to work on and contribute to saving history. These experts are sometimes willing to help for very little money, and occasionally they even raise their own grant funding. Our open source approach is inclusive and  allows others to add new features to the tools, moving the whole community forward.

The downside of this commitment to openness is there is a constant need to raise money, and much of the money we get is earmarked for specific purposes. It’s great to get funding for a project we want to do, like the National Endowment for the Humanities Start-up grant we recently received. However, many of the requirements of running the organization and fostering community growth are not covered by the grant funds.

Funding is critical! We get a lot of volunteer support, we work with students and professors, we get discount rates from many professionals. We are extremely grateful for this help and it makes an enormous difference. At the end of the day, we rely on the good graces of our donors to keep us, and the community, going.



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]



Greek red-figure vases, two surface examination methods and fabricated mock-ups by marlinlum

A linierhaar made of human hair is used to produce looped laid lines similar to that seen in Fig. 10 (left) (photo by Kari Kipper). A 3D elevation map of one such fabricated looped line displays topographical features distinctly similar to the ancient looped line (right). The threshold setting in the elevation map was adjusted to remove the majority of measurements associated with the cardboard substrate. The dimensions of the elevation map are 1.73 × 2.9 mm. The elevation scale bar is in μm.

Paula Artal-Isbrand and Philip Klausmeyer recently published an article in the Studies in Conservation journal.

Entitled “Evaluation of the relief line and the contour line on Greek red-figure vases using reflectance transformation imaging and three-dimensional laser scanning confocal microscopy,” the article examines “…the relief and contour lines on a group of ancient Greek red-figure vases and vase fragments.”

Paula and Philip, both of the Worcester Art Museum in Worcester, Massachusetts, USA, describe how they deployed “… two surface examination methods – reflectance transformation imaging and three-dimensional laser scanning confocal microscopy” to “… characterize the lines and answer questions regarding tools, techniques, and production sequence used by Greek vase painters.”

Their work is interesting and empirical, with numerous examples that yield detailed observations about the tools and techniques used to create the decorative features on vases and vase fragments, with a particular emphasis on relief and contour lines.

Download the entire PDF:

Evaluation of the relief line and the contour line on Greek red-figure vases using reflectance transformation imaging and three-dimensional laser scanning confocal microscopy

 



CHI Welcomes Tom Malzbender to the Board of Directors! by cdschroer
March 21, 2014, 4:02 pm
Filed under: Commentary, News, Technology | Tags: , ,
Tom Malzbender imaging a piece from the Antikythera Mechanism

Tom Malzbender imaging a piece from the Antikythera Mechanism

We are absolutely thrilled to announce that Tom Malzbender has joined the Cultural Heritage Imaging Board of Directors!

Tom is a long-time friend of CHI and has been an adviser and collaborator on many projects. Tom is best known as the co-inventor (with Dan Gelb) of Polynomial Texture Mapping (PTM) in 2001 while he was at HP Labs. PTM is the first form of Reflectance Transformation Imaging (RTI).

Tom has had a long research career in  the fields of computer graphics and computer vision as demonstrated by his many published papers.  He has frequently applied this work to cultural heritage material, most notably as part of the team that deciphered the Antikythera Mechanism. This groundbreaking work was featured in the NOVA documentary  “Ancient Computer”

Welcome Tom!



NEW: RTI glossary now available by cdschroer
March 16, 2014, 10:13 pm
Filed under: Commentary, News, Training | Tags: , ,

Glossary word cloudOver the years we have received a lot of requests for a glossary of terms used in RTI, and we are happy to announce that a new “Glossary of Photographic and Technical Terms for RTI” is available on our website!  It includes photographic terms you need to know for RTI, like “Depth of Field,” “Color Temperature,” and “Aperture.” Also included are technical terms from computer graphics and computer vision like “BRDF,” “Fitting Algorithm,” and “Phong Lighting Model.”  We have included terms for file formats like DNG, XMP and TIFF, along with basics in multi-spectral imaging such as “Infrared” and “Ultraviolet-induced Visible Fluorescence Photography.”  We also included terms related to keeping good process history in your RTI work, including “Digital Lab Notebook,” “ICOM-CIDOC,” and “Empirical Provenance.” We did our best to adapt the definitions for RTI users, and we also included a few notes and recommendations on photographic settings.

As always with our work at CHI, this project was a collaboration.  Lots of folks offered terms they wanted to see defined, and some provided definitions. We especially want to thank Tom Malzbender for definitions for many of the technical terms;  Yosi R-Pozeilov for sharing his extensive glossary of photographic terms; and technical writer Judy Bogart for pulling it all together. And finally, we had a wee bit of funding for this work from the Institute of Museum and Library Services, as part of a larger grant project in their 21st Century Museum Professionals grants.  Much of the work was done through volunteer efforts.

If you value this kind of documentation, along with the free open source RTI software, please consider making a donation to help support it.



A big thank-you to our donors! by cdschroer
February 10, 2014, 6:36 pm
Filed under: Commentary, News

thank-you_banner

What an encouraging way to end 2013: our Annual Giving campaign raised almost twice as much as the previous year! Our donors’ continued support of Cultural Heritage Imaging (CHI) is both touching to us personally and vital to our mission.

Our donors’ gifts enable CHI to develop innovative digital imaging tools and practices and disseminate them to experts and students all over the world. Specifically, this financial support helps us complete software projects, like our recent release of the updated RTIViewer 1.1 and our update to RTIBuilder (coming soon). Donations also fill in the gaps in our funding so we can refine our training materials and develop new instructional programs. We are currently working on a new class in collecting high-quality, accurate, 3D models using a digital camera (stay tuned to learn more about that). CHI also engages in a variety of projects with museums and historic sites, and donor contributions allow us to keep our fees as low as possible for these projects.

In the long run, financial gifts support our many users around the globe who are working on cultural documentation in vital fields such as archaeology, computer imaging, museum and library sciences, natural sciences, and data archiving.

We are deeply grateful to our donors for their generosity.

–The CHI team



Behind the scenes: RTIViewer 1.1 release by cdschroer
December 6, 2013, 2:15 am
Filed under: Commentary, News, Technology

rti-viewer-interface-sm

We are thrilled to announce the release of the RTIVewer  1.1 software!

This update release includes the most asked for features in the RTIVIewer.  As with prior versions, this is free, open source software. We have been working with it for a while, and we are excited to get this out to everyone in the RTI community. I am most excited about surfacing all the numerical settings data within the interface.  Of course those numbers were in the software, but you couldn’t see them or work with them directly.  The new bookmarks and snapshots features take advantage of and keep track of these settings for you.   Read more about all of the new features and how to use them in the updated User Guide.

For those interested in the back story, here is how this release came about.

We had a tiny amount of money in a 21st Century Museum Professionals grant from the Institute for Museum and Library Services to pay for some software updates.  We really wanted to add the support for normal visualizations, as that is incredibly useful both as a visualization of the surface normal data and as a way to compare the calculated normals over time, or across related data sets.  We also heard over and over again that folks wanted to be able to get back to specific views in their RTI file. A significant amount of preliminary work for a bookmarks feature had been done by Leif Isaksen of the University of Southampton.  We picked up his work (with his volunteer help) and expanded it to include interface updates and also to save these details with snapshots.

We were able to procure the development services of Ron Bourret, a senior developer who was willing to do some part time work at a very discounted rate.  When the money for the project ran out, Ron volunteered his services to complete it.  We also had volunteer help from Gianpaolo Palma, of the Visual Computing Lab in Pisa.  Gianpaolo was one of the principal developers of the original version of RTIViewer. Then we had some testers, and time from the CHI staff to oversee it all, test it, prepare material for the documentation, etc.  To complete things, the fabulous tech writer, Judy Bogart, stepped in and updated the user guide, as a volunteer.   We had hoped to ship the release earlier in the year, but once it became a volunteer project, the work had to be fit in around other things people were doing, like travel and paid commitments.

While we are totally happy with and proud of the result, we know that the process can run faster and more efficiently when we have funding. Adequate funding is essential in these releases, even when we get incredible volunteer support.

If you use RTI tools, or if you think they are valuable – please support our efforts.  We suggest a donation of $50 per year for users of the tools and services, like the CHIForums. We are a small independent nonprofit organization and we rely on donations to help support this work. We  appreciate all donations, in any amount.

We accept donations any time, and right now through December 31, 2013 is our annual giving campaign. If you are in the US, your contribution is tax deductible. Thank you for your consideration



Thank You Tim Lindholm! by cdschroer
July 9, 2013, 9:36 pm
Filed under: News

Tim Lindholm, circa 2004

I want to take a moment to thank outgoing board member, Tim Lindholm.  Tim served on the CHI board from its inception in 2002 and has been an enormous help to us over the years.  In addition to being a constant source of good questions and good advice on the board, Tim  designed the electronics and power systems of CHI’s early automatic dome systems.  Tim is an engineer’s engineer, one of those rare folks who can translate between the geekiest geek and the least technical PR, marketing or legal person.  A true gift.  Tim’s love of daguerreotypes and of historical documents and archives makes him care deeply about our work. We will miss him on the board, but he promises to remain a supporter and advisor to CHI.

Early CHI dome system, with electronics and electrical by Tim Lindholm

Early CHI dome system, with electronics and electrical by Tim Lindholm



CHI celebrates 10 years as a nonprofit corporation! by cdschroer
August 16, 2012, 5:47 pm
Filed under: Commentary, News, On Location | Tags: ,

On August 16, 2002 we founded Cultural Heritage Imaging as a nonprofit corporation in San Francisco.  Wow, it seems like yesterday and it seems like a long time ago!  Our digital camera at that time was 3 megapixels and it had a pretty slow auto focus. We had seen Tom Malzbender’s pioneering Polynomial Texture Mapping paper at SIGGRAPH in 2001, and we began working with him several weeks later. However, using the technique required working with command-line software and capturing images using either a lighting array (dome) or a very time consuming detailed template approach.

CHI’s manual RTI rig – 2004

We were shooting some 3D using structured light software from Eyetronics, and we had been on site with Professor Patrick Hunt of Stanford University at his archeological excavation at the Grand St. Bernard Pass in Switzerland as early as 2001.

Mark Mudge, Carla Schroer, and Marlin Lum on location at the Grand St. Bernard Pass in August 2004

We have come a long way since then, working with numerous museums, historic sites, archaeologists and historians, as well as computer science researchers. In 2006 we developed (with Tom Malzbender) the Highlight RTI technique, and we worked with the team at the University of Minho in Portugal to develop open source software to support that (RTIBuilder).  With a grant from the Institute of Museum and Library Services beginning in 2006, we researched a multi-view approach to RTI and out of that collaboration with Professor James Davis et. al. of UC Santa Cruz and the Visual Computing Lab in Pisa came the open source Hemispherical Harmonics fitter (section 6 in the tutorial notes) and the RTIViewer.

Also in 2006 we were contacted by folks at the Worcester Art Museum Conservation Lab interested in using RTI for art conservation. After a small pilot project, we built a light array for them and trained them in the RTI technique. To this day we appreciate this group, their vision of how this technology could be used regularly in their field, and their willingness to go out on a limb to make to make it happen and share their work with others.

Worcester Art Museum Conservation Lab – May 2008

In 2008, as interest in RTI grew on the part of museums and historic sites, CHI made a great effort to develop training programs for RTI and other computational photography techniques.  We have since trained over 200 people in our full 4 day RTI class, and we have introduced hundreds more to RTI through workshops and presentations at numerous conferences and lecture series.

Our current research work includes an NSF funded project with Professor Szymon Rusinkiewicz of Princeton University to further develop the technique of Algorithmic Rendering with RTI data sets and easy-to-use software that includes a way to keep track of the full process history in a digital lab notebook. We began working on the requirements and methodology for how to manage this process history for all of our imaging work and especially RTI back in 2002, and  we shared it with the computer graphics community in 2004 on a SIGGRAPH panel called “Computer Graphics and Cultural Heritage: What are the Issues?” chaired by professor Holly Rushmeier.  Our early work referred to this subject as “empirical provenance,” described in detail in this 2007 paper delivered at the CIPA conference.

So now, 11 cameras, many well-worn travel bags, and I can’t even count how many laptops later, we enter our second decade of collaboration with many wonderful people from all over the planet. We thank some of the folks who have helped us along the way on our acknowledgments web page but it isn’t and can’t possibly be a complete list. CHI was founded on the principles of collaboration and the democratization of technology, producing tools and methodology that enhance scientific reliability and long-term preservation.

We would like to say thank-you to everyone who has volunteered time, donated money or equipment, shared their work, asked us questions, answered our questions, written down how to do things, listened to us speak, formed project collaborations, or run across our path in some interesting way!  We hope to meet you all again, and many others down the road.

Cheers!