My name is Sue Grinols and as the director of photo services and imaging, I witness the intersection of art and technology on a daily basis. This is an exciting time to be working in photography. Just seeing how technology is changing the field can be breathtaking, not to mention challenging.
Photographing artwork is a sub-specialty of studio photography. Here at the Museums, we use the same equipment and techniques as photographers who produce beautiful images of cars, perfume bottles, leather couches, and the perfectly grilled steak. But instead of trying to capture the steak’s sizzle or the couch’s inviting warmth, we attempt to bring out the essential character of the artwork while emphasizing its sublime beauty whenever possible. When we’re not doing that, we can make images that show the hard, cold details of an object in order to help conservators as they work through treating the artwork, or to help curators in their scholarly study of an object. It is this second type of photography that I want to blog about today.
What is RTI? It's a form of photography (with a lot of math behind it) that creates a highly detailed image of the surface of an artwork. In a nutshell, you take a series digital images, typically 36, of an object using a strobe light. After each shot, the light is moved slightly so that it illuminates the artwork from a different angle. Special software is then used to combine those images into a single RTI image, which can be viewed interactively on a computer. By mathematically enhancing the RTI image, an artwork’s features appear in sharp relief in a variety of different lighting scenarios and you are able to see details of the surface that are otherwise not visible (or very difficult to see).
Back in San Francisco, CHI provided a demonstration of the RTI technique to the Museums' conservation staff, which generated some keen interest. So we decided to try it out on one of our Egyptian coffins.
Fast forward to late 2009 when CHI won a Kress Grant to determine the way RTI can be of use to conservators. Since we are both based in San Francisco, CHI approached the Fine Arts Museums and asked us to work with them on this project.
Next, museum conservators picked out a variety of objects to photograph using the RTI technique. The CHI team came to document the whole process armed with their still cameras, tripods, video cameras, good humor, and expertise.
The results were surprising. We could see more details in the artwork than we expected.
Here is a standard collection photo of a 16th-century enamel:
Another object we photographed was our Hirosada woodblock print, which was included in last year's exhibition Japanesque: The Japanese Print in the Era of Impressionism.
With the RTI results, some very subtle details become apparent. Note, for example, how the figure's furrowed brow is actually embossed to emphasize the expression!
You can see more details about these RTI results in the extended movie (which was on display during the Japanesque exhibition) at the bottom of this page.
Here is a standard collection photo of one of our paintings:
Now, here is a detail from the RTI image. You can see the brush strokes the artist used, which speaks to his technique: notice how some of the paint was applied in the same way you might apply makeup around an eye.
To make a long story short, the results from the grant were a success! We clearly proved that this technology is a valuable tool for conservators. CHI created a documentary about the process, which features many of our conservators.
Next on the list of objects to be photographed using this technique is one of our 5th-century Greek pelikes. Here is the standard collection photograph of the object: