Cultural Heritage Imaging


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:

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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.



In honor of Debbie Ward by cdschroer
December 13, 2012, 12:56 am
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.

I want to say THANK YOU!  to all who donated in Debbie’s honor. We promise to put the funds to good use in supporting our mission and programs, and in spreading our work around the world.



Join us! New Free Forums for the RTI Community by cdschroer
September 24, 2012, 11:42 pm
Filed under: Commentary, Grants, Training

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



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!



Zero Out Settings by marlinlum
June 27, 2012, 9:01 pm
Filed under: Commentary, Training, Uncategorized | Tags: , , , ,

During the post processing phase, when you open your DNG files in Adobe Camera Raw (ACR), you have an opportunity to adjust your white balance and your exposure compensation. Prior to making these adjustments …

We recommend that you create a “Zeroed Out Settings” custom preset, and apply it to the entire image set. Consider making this your default preset for Adobe Camera Raw. To do this, set all of the settings to 0, then save as a named preset using the flyout menu for the Basic image adjustments panel. In particular, make sure all sharpening options are set to 0.

zero out settings

Make sure that your Zero Out Settings match the above screen shot (click image).

Check the settings in all of the tabs. The first three tabs (Basic, Tone Curve, and Detail) have default settings that are non-zero; the radius setting on the Detail tab cannot be less than 0.5. In other tabs, default settings are already zero. (as taken from page 5 in the RTI Highlight Processing Guide v1.4)

‘Zeroing Out’ data ensures that your data is not being processed, interpreted or stylized to fit consumer tastes.



Reconnaissance. Scouting. Preparation. by marlinlum
June 22, 2012, 7:41 pm
Filed under: Commentary, On Location, Workshops | Tags: , , , ,

Reconnaissance. Scouting. Preparation.

Marlin Lum here. Imaging Director at Cultural Heritage Imaging. This blog entry inspired by Mark Christal, strong man and multi-media super genius employed by the National Museum of the American Indian (NMAI) at the Mall in Washington DC. It’s part of his professional game to find out as much as possibly about a topic and then present it to the public via modern visual technology. Go to the National Museum of the American Indian and check out what they are putting out in the world, really good stuff.

River Bed Pano

panorama photograph: scouting for rock art in a river bed

Mark is a graduate of CHI’s 4-Day RTI Training and a NCPTT Workshop participant where he not only refined his skills in RTI capture but also learned about photogrammetry. Aside from being a respected technologist and dedicated vegan, he is also an enthusiast of ancient Rock Art. (no- not album covers). Native American rock art.

Taking his Panorama and RTI capture skills in the field, (meaning a 14 mile mountain bike route, hot weather, lots of photo gear on back), Mark and his crew (also (former) NMAI super genius Video Master, Kevin Cartwright) entered the wilderness on a reconnaissance mission. Mission: to locate a petroglyph, shoot a Pano and scout it for future RTI capture.

I also have to mention, as stated by Mark, ‘that the park ranger had never heard of this (culture) site’. Mark and Kevin only found it after actively looking/hunting, and having followed a good tip from a kayaker. According to Mark, ‘this might be the only known on-site rock art in Maryland’. Mark goes on to say that, “The only other site (Bald Friar) was dynamited in the 20’s because it was about to be flooded.  Parts of that site are now spread across the state in a number of museums and culture centers”. Uhmm. Can you say, ‘sense of urgency’, get out there and document people!

A long time ago I used to work in Hollywood where I knew a location scout. It was his job to discover everything, everything about that location and bring that information back to the unit. His checklist asked questions like: Where is this on the map? What direction does it face? Where is the afternoon sun? Can I get a crew here? Do I need extension cords? Whats the scale of the artwork? What lens do I need? Is my tripod in dirt or water? Who’s land is this? What’s the deal with the roaming horned bull? (true story btw). And where is the crew bathroom?

You get my point. The more you know about your subject (and its owners {past and present}, the better). A thorough knowledge base about what exactly you intend to RTI is essential for creating a successful final product. It’s like anything else, knowing what equipment you’re gonna need (and what you don’t want to carry {or bike} for 14 miles) is gonna make or break it (your back that is).

Hollywood crews might research and setup a shot for months, only to have the actor whisper his lines in 40 seconds.

I will draw a conclusion to this blog and just point you to the large JPEG that Mark Christal email me from his Recon mission into the hot sun. (For those of you shooting in the comfort of a photo lab, you will have your chance.)

Mark’s Recon Pano gives us a glimpse into the beauty, the full shade during full sun, the water level during that time of year, the artwork and the scale (note calibration stick). And for those of you who are curious, yes, this location IS top secret, so, no use in hacking or looking. One last thought, shoot a capture when the water is running low.

Scout and be happy!

check out the flat pano image here on Flickr! Click on the Hi-Res image – can *you find the rock art? (look for the calibration stick)

Go directly to a large the jpeg: http://www.flickr.com/photos/markchristal/3938203809/sizes/o/in/photostream/



RTI Experimentation with a Copper Breastplate in the Florida State Bureau of Archaeological Research by marlinlum

This is a Guest Blog by Photographer Joseph Gamble.

As an affiliate with the University of South Florida’s Alliance for Integrated Spatial Technologies, I traveled with a team of archaeologists doing imaging research and 3D laser scanning of artifacts to Tallahassee last year to work in the Florida State Bureau of Archaeological Research (BAR) and experiment with RTI on a number of Native American artifacts from Lake Jackson, Florida. AIST Directors, Drs. Travis Doering and Lori Collins along with AIST archaeologist Dr. Jeff DuVernay, helped me to manage a challenging RTI of a Native American copper breastplate as well as other copper and metal objects from Lake Jackson and several other Florida sites.

Native American copper breastplate from Lake Jackson, Florida

The artifacts were from the ancient Lake Jackson settlement, a civic-ceremonial center of a Mississippian chiefdom that flourished across parts of northern Florida between c. 900-1500 A.D. The breastplate (23 X 54 cm) was cold-hammered from a sheet of native copper and contains extensive iconographic and symbolic that today are faint and difficult to discern. In the 1970s, the piece was encased in a clear Plexiglas, cube-like chamber that had been infused with argon gas as a conservation measure to halt corrosion of the artifact. The reflective polymer barrier that enclosed and protected breastplate seemed to pose an insurmountable obstacle for its accurate high resolution documentation. To stabilize the breastplate it had also been pressed into a plaster base to prevent further fragmentation and distortion leaving the piece with a cracked or crenelated surface texture. This condition was an additional for the documentation because of the shadowing that further limited the usability of the image set.

To acquire an inclusive data set that would contain sufficient usable images to build an RTI, we placed the case on black velvet, mounted the black balls and commenced to shoot. The total image count came to 156 raw files of which 57 were used to build the RTI file and, much to our delight, it worked well.

View the Final RTI File by clicking here (you tube video).

Joseph Gamble is a previous 4-Day RTI Training graduate. You can learn more about Joseph Gamble Photography at: http://www.jcgamble.com/

You can learn more about the Alliance For Integrated Spatial Technologies at: http://aist.usf.edu/