Filed under: Commentary, News | Tags: Anna Ressman, cultural heritage imaging, Digital Imaging, Oriental Institute Museum, Reflectance Transformation Imaging, RTI, Technology, University of Chicago, visualization
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).”
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]
Filed under: Commentary, News, Technology | Tags: Antikythera Mechanism, PTM, RTI
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”
Filed under: Commentary, News, Training | Tags: glossary of terms, photographic terms, technical terms
Over 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.
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
Filed under: Commentary, Guest Blogger | Tags: color card, Dan Kushell, gray card, grey card
Feeling gray? How about some shades of gray?
Have a new studio? Want to paint it photographic neutral gray? Read on for important information and advice.
The information quoted below was authored by Dan Kushel, Distinguished Teaching Professor Emeritus at SUNY Buffalo State, New York, USA.
Recent photographic lab renovations at Buffalo State College required the walls to be painted a fresh coat of gray. Rather than randomly select a “nice” neutral gray, Dan Kushel took a more methodical approach.
Dan allowed us to share a PDF with the data that was produced from his careful research.
Download the PDF : neutral_gray_paint_laminate_reflectance_spectra-1
Commenting on his project, Dan stated:
“We used all three paints in the new conservation imaging laboratories which were just completed. The choice (of gray) depended on function. The 18% N5 was used in the main photographic and reprographic studios; the 40% N6.5 in the image processing studio; and the 60% N8 for the chemical dark rooms and X-ray room.”
As noted in the PDF file, “neutral_gray_paint_laminate_reflectance_spectra-1.pdf,” the reflectance spectra of three neutral gray Benjamin Moore paints are fairly comparable to Munsell N5, N6.5, and N8 (18%, 40%, and 60% average reflectance).
The three are respectively: “Steel Wool” 2121-20; “Sterling Silver” 1461; and “Pelican Gray” 1612. Note that the neutrality of “Sterling Silver” is compromised above 650nm where reflectance sharply increases into the near infrared. All spectra were made by averaging five readings of the surface.
The PDF also includes spectra of the N5, N6.5, and N8 patches on a new X-Rite ColorChecker for reference.
Also in the PDF are reflectance spectra of three neutral gray Formica laminates. They are: “Mouse” 928-58 (20% reflectance); “Fog” 961-58 (30% reflectance); and “Folkstone” 927-58. Neutrality is quite good on all of these.
Reflectance spectra of the paints as applied to the walls closely matched the spectra of the samples we originally measured. These paints should all still be commercially available.
Thanks to Dan for allowing us to share this great work!
Below are some links to the pigments:
- • “Steel Wool” 2121-20
- • http://www.benjaminmoore.com/en-us/paint-color/steelwool
- • “Sterling Silver” 1461
- • http://www.benjaminmoore.com/en-us/paint-color/sterlingsilver
- • “Pelican Gray” 1612
- • http://www.benjaminmoore.com/en-us/paint-color/pelicangray
- • “Mouse” 928-58 (20% reflectance)
- • http://www.cabinetparts.com/p/formica-laminate-sheets-for-countertops-FORM928204X8
- • “Fog” 961-58 (30% reflectance)
- • http://www.cabinetparts.com/p/formica-laminate-sheets-for-countertops-FORM961104X8
- • “Folkstone” 927-58
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
Filed under: Commentary
Adam Rabinowitz’s Blog Post “The Work of Archaeology in the Age of Digital Surrogacy” is a brilliant thought provoking piece, and I couldn’t resist reposting here.
At CHI we have been wrestling with issues of scientific imaging and process history and what it means to be a digital surrogate for many years. As a classicist, Adam shows us that these issues aren’t new and that reproductions and surrogates and the issues surrounding them for scholarly inquiry go back millennia.
Thanks Adam, for a thought provoking piece!
Guest Blogger: Sarah M. Duffy Ph.D.
Serendipitously while completing my Master’s in Historic Preservation at University of Texas at Austin, I met Carla Schroer and Mark Mudge of Cultural Heritage Imaging (CHI) at the 9th Annual US/ICOMOS International Symposium being held in San Francisco in 2006 where they were demonstrating the application of an innovative recording technique based on a mysterious shiny black ball. I was utterly amazed by the results they were able to achieve using a flexible, inexpensive recording approach they called Highlight-RTI (H-RTI). Corresponding with Cultural Heritage Imaging further after the conference, I decided to incorporate the technique as a major component of my graduate research at an ancient Ukrainian site called Chersonesos (2007). Having only seen their demo, I relied heavily on their electronic support during my first RTI test runs, successfully producing a set of images suitable for creating a Reflectance Transformation Imaging (RTI) after a couple of trials. In 2008, I was able to attend a CHI RTI training class at the Tauric Preserve of Ancient Chersonesos in Ukraine, that was supported by the University of Texas at Austin.
I took those early experiences with RTI into my PhD research in the Archaeology Department at University of York which more broadly examines the application of digital recording techniques within the archaeological process of investigation. Although RTI is not my focus, I continue to explore its advantages, most especially in terms of how the approach enables specialists to advance the understanding of the recorded archaeological resource. While completing my doctoral work, I was asked to produce guidance on RTI by English Heritage (the Historic Buildings and Monuments Commission for England).
Accordingly, Multi-light Imaging for Heritage Applications was launched at the Digital Heritage 2013: Interfaces with the Past conference held at the University of York, United Kingdom on 6th July. The publication aims to offer user-friendly guidelines and advice for using the H-RTI capture method. Alternative RTI capture methods are also introduced so that readers are able to decide which capture method is most appropriate for their recording project. Several case studies demonstrate how the technology can be used to better understand the cultural heritage we record and provide solutions to some of the common challenges encountered while using this recording approach. Quick reference tips are provided throughout the document as well as links to useful publications and websites, such as the principal sources for the freely available processing software (Cultural Heritage Imaging and Hewlett Packard Labs). Contributors include Paul Bryan, Graeme Earl, Gareth Beale, Hembo Pagi and Eleni Kotoula.
The publication is freely available through English Heritage.
Filed under: Commentary
In the summer of 2012 I lost a dear friend of more than 20 years to lung cancer. Debbie’s and my friendship began in the workplace in the late 80′s, and blossomed into so much more. We hadn’t worked together in more than 20 years, and yet we stayed in close contact and got together for regular dinners every couple of months. Debbie was a remarkable person in many ways, but if you asked her what the most important thing she ever did was, she would say being a mom to Katie. After Debbie’s passing, I was touched when Katie told me she had selected Cultural Heritage Imaging as her mom’s favorite charity and one she would ask Debbie’s friends and colleagues to support in her honor. I was genuinely moved when her colleagues at PG&E and other friends raised more than $1500 in her honor. Wow!
Debbie was a long time supporter of CHI making an end of year donation every year in varying amounts depending on what she could afford. She was also someone who provided moral support, by gently encouraging me to keep going, even when the work and the fundraising felt overwhelming. She told me me how important she thought CHI’s mission was, and she especially liked that we were helping others create lasting records of cultural heritage materials that would be around for her daughter and someday maybe her as yet unborn grandkids. I miss her.
This week we are rolling out CHI’s new free forums for the community of people who are developing and adopting Reflectance Transformation Imaging (RTI) and related computational photography. We have had the idea to do this for some time, and after trying a couple of different forum software packages, getting input from friends, and tinkering with some of the forums setup, we are now ready to invite the larger community. Join us! Sign up for a forums account now: go to http://forums.culturalheritageimaging.org and click the link “Sign In” in the upper right of the window to begin setting up your new account. You can look at content in the forums without an account, but a free account is required to post there (this is to keep the spammers at bay).
As our RTI training has expanded, and more people are adopting RTI, we are frequently asked how users can see what other people are doing with the technology, and whether CHI offers a place to find answers when difficulties arise. We know many people want to keep up with the latest news on software releases, equipment, and related topics. Our forums were created to answer these needs. We hope to see the RTI community help each other and share their experiences and insights.
I’d like to say thank-you to those who made this new forums service possible. First, thanks to the Institute of Museum and Library Services (IMLS) because we were able to use a little funding from our 21st Century Museum Professionals grant to get the forums going. This grant, which has enabled 10 4-day training sessions in RTI — we just finished the 9th one this month — has also helped us support updates to our software, user guides, and other materials associated with the adoption and use of RTI at museums and libraries. Sarah Ross did a fine job installing and setting up the forum software for us! The team at CHI has already added content to get the forum going and answered questions that have come in. We have had a great group of beta testers who tried this out, posted content, and gave us feedback.
We hope that you, members of our community, will engage in the forums, asking and answering questions to help each other. This is just the beginning; we plan to expand the forums to cover additional topics as the need arises. Please write to us and let us know what you want from the forums: what will make them the truly useful for you? Send your comments or questions in an email to: forums at culturalheritageimaging.org