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April 22, 2005
An Interesting Article About the Problems of Digitizing
I am currently pushing on my colleagues at the library a very interesting article by Richard Preston that appeared in the April 11, 2005, issue of The New Yorker about the digitization of "The Hunt of the Unicorn" tapestries from about 1500 that hang in The Cloisters, the branch of the Metropolitan Museum of Art in New York that displays medieval art.
In the process of restoring the tapestries, the museum decided to digitize them, both front and back, so that there would be a permanent digital record preserved in case a catastrophe caused the destruction of the artifacts themselves. The museum hired very reputable consultants and photographers to make very high resolution images of the tapestries. The images were made in segments, with the idea that they could be "stitched together" into a seamless single image using Adobe Photoshop software. But when the museum staff tried to do so, they found that the images were far too large (filling more than two hundred data CDs) and complex to manage.
The museum then turned to two mathematician brothers, Gregory and David Chudnovsky. The brothers are number theorists and built their own supercomputer out of mail order parts. Their previous claim to fame had been to using their homemade supercomputer to calculate the humber pi to beyond two billion decimal places. The brothers thought that assembling the images would be a piece of cake.
But when they made their first attempt, it failed, and the Chudnovskys had no idea why. Upon further investigation about the process used to digitize the tapestries, it was discovered that they had changed shape very subtly while lying on the conservation lab floor being photographed. The Chudnovskys realized that they were working with an image of a three-dimensional structure. This required the brothers that they would need to recalculate every pixel of every image in order to make the image of the tapestries and to correct for subtle differences in color that had occurred during digitization. It was a series of computations, taking three months with their supercomputer, comparable to that of DNA sequencing. After the computations were completed, the final assembly of the first image took twenty-four hours of supercomputer time.
At the end of the article, Richard Preston, the author, describes revisiting the restored and re-hung tapestries at The Cloisters. Despite the phenomenal technological feats that had been used to create the digital image, the real things were still vastly superior, "full of velvety pools and shimmering surfaces, alive with color and detail. ... In comparison, the digital images, good and accurate as they were, had seemed flat. They had not captured the translucent landscape of the Unicorn tapestries."
Posted by tdr at April 22, 2005 03:46 PM
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