Cultural Heritage Imaging


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



Feeling Gray? How about some Shades of Gray? by marlinlum
January 17, 2014, 7:05 pm
Filed under: Commentary, Guest Blogger | Tags: , , ,

Image

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.”

Testing the “spectra” was not a difficult process, and the “i1 and Robin Myers SpectraShop” tools were utilized to gather the data.

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:

Benjamin Moore

Formica laminates:

Comments Off on Feeling Gray? How about some Shades of Gray?


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



Adam Rabinowitz’s blog post on digital surrogacy by cdschroer
November 15, 2013, 4:29 am
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!

 



Behind the Scenes of a New English Heritage guide for RTI by cdschroer
August 2, 2013, 5:38 am
Filed under: Commentary, Guest Blogger

Guest Blogger: Sarah M. Duffy Ph.D.

Multi-light-coverSerendipitously 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.