“Multi-Light Imaging for Heritage Applications”

Multi-Light Imaging cover

In this free publication by English Heritage, the English Government's advisory body on conservation of the historic environment, the authors describe reflectance transformation imaging (RTI) and offer practical guidance on its application. CHI is prominently cited for its role in the evolution of the RTI technique. More…

RTI Project: University of Southampton

Dr. Graeme Earl of the Archaeological Computing Research Group at the University of Southampton in the UK, has been working collaboratively with experts at the University of Oxford to apply and help advance RTI imaging in archaeological studies. More…

RTI Question? Ask on the CHI Forum

CHI offers a free online forum site where you can share your questions, insights, and issues to gain a more complete understanding of RTI and its practical applications. How are museum conservators, computer scientists, natural scientists, photographers, and other related professional groups using RTI? What problems are they solving and what challenges are they facing? Join the conversation!

Video: RTI and Art Conservation

RTI study in conservation

Watch this 23-minute video on Vimeo, produced by CHI in collaboration with the Fine Arts Museums of San Francisco and supported by a grant from the Samuel H. Kress Foundation.

RTI Study: Chersonesos, Ukraine

Stele of Kotticha, wife of Damatrios

Late Classical stele, Chersonesos, Ukraine

Learn about a 2008 project in which CHI worked with Ukrainian scholars, archaeologists, and scientists from the University of Texas to preserve and share amazing artifacts from a world-class archaeological site in Ukraine. More…

PTM/RTI Study: Antikythera Mechanism

Antikythera Mechanism

Antikythera Mechanism, 80 BCE

You can view former HP Labs researcher Tom Malzbender's page describing the application of Polynomial Texture Mapping, an early version of RTI, to the Antikythera Mechanism, an ancient astronomical computer built by the Greeks around 80 BCE. More…


More Examples of Reflectance Transformation Imaging

With the widespread growth of interest in RTI, several independent projects that demonstrate its application and efficacy have sprung up around the world. Here are some further examples.

Project: Squeeze Imaging at the Smithsonian

Detail of cuneiform squeeze

Detail of cuneiform squeeze. Ernst Herzfeld papers, Freer Gallery of Art and Arthur M. Sackler Gallery Archives.
Courtesy of Smithsonian Insitution's Museum Conservation Institute Imaging Studio.

In 2010, a team of specialists funded by the Smithsonian Institution's Collections Care and Preservation Fund used RTI imaging at the Freer Gallery of Art and the Arthur M. Sackler Gallery Archives to study a collection of 393 squeezes from ancient archaeological sites in the Near East. A squeeze is a series of sheets of paper that are layered on top of each other and moistened to create a wet pulp. This substance is pressed upon the inscriptions, creating a paper mold and capturing the impressionistic writing for a 3-dimensional negative effect. Often made of paper that varies in quality, squeezes can be fragile, which limits their accessibility and jeopardizes the historical data they hold. The examples in this collection are from the Ernst Herzfeld Papers and date from 1911–1934. The Archives collaborated with the Smithsonian Institution Museum Conservation Institute (MCI) to create a digital preservation surrogate for each squeeze, using Reflectance Transformation Imaging (RTI).

How to View Interactive Files of the Squeezes (Re viewing, see our note below.)

The Smithsonian's Squeeze Imaging Project has put nearly 400 interactive files on the web in an earlier form of RTI called PTM or “Polynomial Texture Mapping”). See their pages devoted to this area of research:

Note: To view any of the interactive PTM files on the Smithsonian page, click one of the sites listed in the right column (“ARCHAEOLOGICAL SITES”). On the resulting page, click the link under the title to see the actual squeeze images. For more information, read the instructions here: How to View an RTI File.

Video: “Japanese Woodblock Prints and RTI”

The short video embedded below focuses on the results of an RTI project conducted by Cultural Heritage Imaging on a mid-19th-century Japanese woodblock print by Konishi Hirosada. The print, which depicts the Osaka actor Mimasu Daigoro IV, is in the collection of the Fine Arts Museums of San Francisco. Through the application of RTI imaging, the print's embossed and textured surfaces are revealed, enabling a better appreciation of the artist's method and technique and the complexity of the woodcut prints.

Japanese woodblock prints and RTI from Cultural Heritage Imaging.

Sue Grinols, Director of Photo Services and Imaging for Fine Arts Museums of San Francisco (FAMSF), wrote about the work with CHI in her blog. She and a group of her colleagues have been using RTI to gain better understanding of objects in their permanent collections.

Study: Applying RTI to a 5th-Century BC Greek Pelike

5th-century Greek pelike

Greek red-figure pelike, late 5th century BCE
Legion of Honor Museum Collection

In May 2011, Sue Grinols and her team from Fine Arts Museums of San Francisco (FAMSF) completed a round of RTI photography of this 5th-century Greek pelike. You can read more about this study in Sue Grinols's blog.

Study: Using RTI to Analyze Decorative Techniques on Red Figure Vases

5th-century Greek stamnos

Stamnos attributed to the Tyszkiewicz Painter, c. 480 BCE (Worcester Art Museum, 1953.92)

In July 2011, the CHI team conducted a training session at the Worcester Art Museum in Massachusetts with the staff at the conservation lab, as part of our IMLS-sponsored 21st Century Museum Professionals program. Decorative features on a Greek red-figure stamnos in the museum collection were examined using RTI and scanning laser confocal microscopy. These two surface examination tools helped to answer questions relating to the decorative process, particularly the tools and techniques that Attic painters used to create the so-called glossy black “relief lines” and “relief dots”.

You can read more about this study here: