Special Photography for Larger Objects: Photogrammetry

By Christy Ching

Conservation Technician Christy Ching photographing the underside of an Egyptian coffin 2017-20-1.3 for photogrammetry.

One project I have really enjoyed working on as a pre-program conservation technician is documenting larger objects for a process called photogrammetry. Photogrammetry is a technology that gathers spatial and color information of an object from multiple photographs to form a geometrically corrected, highly detailed, stitched image called an orthomosaic. Essentially, photogrammetry creates a distortion-free, three-dimensional model of an object based on two-dimensional photos of every surface photographed in sections. 

Left: Four photographs of an ancient Egyptian coffin lid L-55-16B at various angles, which were used to create a 3-D model. Right: 3-D model draft of L-55-16B.

*L-55-16B (21-46-9) is a loan object from the Philadelphia Museum of Art (PMA)

This can be done for objects of any size. However, we are mostly reserving this technique for larger objects, specifically larger textiles and Egyptian coffins. This is because photographing the coffins and textiles normally with a single shot requires a greater distance between the object and the camera in order to fit the entirety of the object into the frame, and doing so reduces the image quality. Not only that, but the camera distortion that is inherent in all photographs will become more obvious. The resulting image will not be an accurate representation of the coffin or textile, which is not ideal for documentation purposes. 

The image on the left is a single-shot photograph of L-55-16B while the image on the right depicts the same coffin lid created by photogrammetry. When comparing the two images, the camera distortion in the single-shot photograph can be seen especially in the feet and head of the coffin lid.

With photogrammetry, we can take parts of the 3-D model and use them as high resolution, distortion-free, 2-D images of the object instead.

Six views of L-55-16B depicting the top, interior, and the four sides of the coffin lid generated using photogrammetry.

So far, a little less than ten coffins, a few textiles, a pithos fragment, and a giant granite relief have been documented using photogrammetry. The models and orthomosaic images are all generated by Jason Herrmann from CAAM, and we are very grateful that he is doing this for us! To learn a little bit more about the photogrammetry process, view this Digital Daily Dig here.

This project was made possible in part by the Institute of Museum and Library Services.

Confidentially, not so much

Hi everyone. Lynn Grant, Head Conservator here. Last fall, with a certain amount of hoopla, we started a series called ‘Conservation Confidential‘ which was a once-weekly version of the Digital Daily Dig. Well, it was fun but it was a lot more work than we’d expected and we’re already operating at reduced capacity thanks to the need for distancing. Also, we got very few questions. So, in this new year, we’ll be doing the Conservation Confidential on the last Friday of each month (Final Friday). In the meantime, we’ll try to be more proactive about blog posts and will seek other ways to connect with our virtual and on-site visitors (The Museum reopens this Friday) As always, if you want to chat with the conservators, use the Ask Us link in this blog.

Conservation Confidential: Scaling Up

Check out today’s Conservation Confidential, Scaling Up: Treating Monumental Architecture with Julia Commander, Alice and Herbert Sachs Egyptian Collections Conservator. Get to know the museum’s Conservation Lab Annex and the big things going on there.

You can also catch up with other posts in this series here.

Conservation Confidential: Tools galore!

Today’s Conservation Confidential, Tools of Every Trade: Conservation Ingenuity with conservator Lynn Grant can be viewed at vimeo.com/483259426. You can also catch up with others in this series by looking in the Conservation Confidential section at https://www.penn.museum/events/adult-programs/the-daily-dig. Many of today’s stories and images were drawn from our 8 years of Artifact Lab blogging. If you want to know more, here are links to the relevant posts:

  • Molly’s tools:  https://www.penn.museum/sites/artifactlab/2015/08/17/the-right-tools-for-the-job/
  • Gel Cleaning: https://www.penn.museum/sites/artifactlab/2017/12/08/coming-clean/
  • Restringing: https://www.penn.museum/sites/artifactlab/2018/05/16/beaded-necklaces-restringing-to-secure-the-past/
  • Kitchenwares: https://www.penn.museum/sites/artifactlab/2017/04/11/cleaning-questions-and-cross-sections/
  • https://www.penn.museum/sites/artifactlab/2017/12/08/coming-clean/
  • https://www.penn.museum/sites/artifactlab/2013/01/10/making-scarab-amulet-impressions-part-2/

Cuneiform Conservation Conundrum

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One of the earliest known forms of writing is cuneiform, a wedge-shaped script developed by the Sumerians, around 5000 years ago. It is preserved on stone carvings and clay tablets. The survival of the clay tablets is amazing, given that most were of unbaked clay – essentially mud. Today’s Conservation Confidential (1 pm EST on Penn Museum’s Facebook page) will feature conservator Tessa de Alarcon discussing the preservation of these earliest written records.

Palm trees and Sharks’ Teeth, oh my!

In today’s Conservation Confidential, Project Conservator Debra Breslin will discuss her work on some amazing objects. How do you wage war when your only raw materials are palm trees and fish? What’s Robert Louis Stevenson got to do with it? To find out, tune into Penn Museum on Facebook at 1 pm EST or check it out asynchronously (as we like to say these days) at the Conservation Confidential section here

Conservation Confidential: Sphinx Gallery tales

Join Schwartz Project Conservator, Molly Gleeson, as she brings you up to date on what’s been happening in our Lower Egyptian Gallery for the last two years. Lots! Almost all of it pretty monumental. Molly will be available to answer questions via the Penn Museum Facebook page between 1 and 2 pm EDT on Friday, November 6.

Conservation Confidential: Moving Monuments

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This month, the Museum is celebrating CultureFest so our next Conservation Confidential relates to some of the work done in renovating our Mexico and Central America Gallery. Project Conservator Alexis North will describe the eventful journey of some of the Maya stelae from the jungles of Belize to their current locations, with a few adventures along the way.

Conservation Confidential will go live at 1:00 pm EDT this Friday on the Penn Museum Facebook page. Tune in to watch and ask questions live from 1 – 2 pm. Can’t make the live version? No problem, you can see the archived version here, under the heading Conservation Confidential, and post any questions or comments on our blog.

Conservation Confidential launches!

Penn Museum’s Daily Digs have been a popular offering since their beginning in the fall of 2018. They gave Museum faculty, staff, students, and volunteers chance to rhapsodize about some of their favorite objects or subjects. The in-gallery, in-person versions had to give way to virtual versions when the Museum closed this spring and have continued as the Digital Daily Digs, every day at 1 pm on the Museum’s Facebook page. While conservators have often participated both in the gallery versions and in the digital format, on October 16, we’re starting something new.

Each Friday, a member of the Conservation team will ‘take over’ the Digital Daily Dig with something we’re calling ‘Conservation Confidential’ – a short intimate look at a conservation topic. In honor of International Archaeology Day, Julia Commander will lead off the series talking about her work at the Museum’s site of Gordion, in Turkey.

The inaugural Conservation Confidential was posted at 1:00 pm EDT this Friday on the Penn Museum Facebook page. This post was supposed to go up that morning but somehow the scheduling function didn’t work (This is Lynn Grant, Head Conservator, writing this and apparently I failed that part of WordPress). Please watch this great presentation, post any questions or comments on our blog and look out for a new Conservation Confidential this coming Friday.