Marymount Metro Humanities Portal

Review of: Dr. John Delaney’s Advances in Infrared Reflectography (2/13/2012) Dr. Delaney is a physicist working with the NGA curatorial division who has been advancing the technology available to researchers. Specifically, during his 5 years with the group, his latest advances come in the form of ground-breaking camera improvements as well as improvements in image processing, allowing examination not just of the normal underdrawing of a painting, but overwritten layers as well as on drawings and illuminated manuscripts. The technical improvements were done in conjunction with advances with the George Washington University’s School of Engineering helping on the technical side.

Much of the presentation referenced technical information on light levels and the how and why the two new camera modes were improvements over the existing equipment. After explaining how red-shifted light (that is, moving into longer wavelengths) can penetrate down to the Gesso layer and reflect only the black of the sketch and the white of the Gesso, he explained how new developments in multi-spectral cameras allow for even further infrared (IR) range allows the camera to minimize even some of the top and middle layers of the underdrawing. This pulls out the earliest and lowest-level sketches, showing what an artist originally had planned on the material in question. Standard IR scanning is in the 1100-1400nm wavelength (visible light is in the 400-700nm range, for reference), but the improved multi-spectral camera can push the wavelength to extend from 1000-2600nm, opening up new territory in what can be found. It still is an overnight process for an entire painting, however.

The real advantage shows up when combined with three layers from the second camera advancement, the hyper-spectral camera. This camera utilizes three passes on a work of art, hitting it with false red-range IR (2100-2400nm), false green (1500-1800nm), and false blue (1100-1400) wave beams. Now, I say false because, as infrared, it isn’t actually those colors. Instead, what the wavelengths do is bounce differently off chromatic ingredients in the painting and underdrawing, such that blue tones show up differently than red, and reflective metals do so differently as well. This leads to three different images, which are false-colored by computer process slightly to show the discrepancies between the three images. When combined into a single image, the false color composite shows which drawings are on top, underneath, and which made the transition between the first and final drawing. If compared to a multi-spectral image, the two can identify minute details that either were not previously visible, or a matter of excellent attention to detail. Dr. Delaney had several false-color scans of Jan van Eyck’s Annunciation as an example, as well as a close-up of Leonardo’s Ginevra di Benci. The van Eyck shows small changes through the face of the Madonna in the new camera techniques, while the Leonardo work shows very now-easily visible pouncing for Ginevra’s eyes, nose and mouth.

The second group of improvements come in the form of image processing enhancements. It basically is a matter of telling the software handling the image how to better differentiate parts of the underdrawing from interference. Much of this is a matter of upgrading the software to work with the new camera technology, and for this part, Dr. Delaney seemed to refer back to the cameras as the primary implements. That said, it was during this part that the opportunity to scan both drawings and illuminated manuscripts to look for more detailed differences became the focus of the presentation. While a hyper-spectral camera can allow for a tri-false-color image, the composite is the software’s job, along with telling it to highlight areas where Iron Gall ink, silverpoint or lead were used. As such, the software can effectively provide another set of eyes to pick out details that may have been missed with the eyeball Mk. I. Among this details are watermarks and drawings on the backsides of other works, which often would have the disadvantage of being reversed and possibly off-axis, making recognizing them harder for a normal down-is-down researcher. Moreover, the software can take the two image formats a step further and identify what kind of density the artists had to use with certain materials. While gold will bounce the IR scans back (due to the reflective properties of the metal), the other expensive ingredient, Lapis Lazuli, can be scanned across the 1000-2600nm range to find out where the artist had to repeated paint over to get the desired effect.

The audience had a few questions during the 12:10 session, one of which stands out as a very interesting window of opportunity. The question was whether or not this technique could be applied to non-flat artifacts, such as vase or statues. The response Dr. Delaney had was that the real issue there is that the degree of relief from surface to back of the item, unlike in a flat painting, changes drastically over the surface of the artifact. In effect, the three-dimensionality is the curse that would impede doing so, but he did mention that certain artifacts would be good test cases and that it may simply come down to being a time-intensive process.

In all, the advances in camera technology and software processing give a very interesting view at what could have been, and even moreso at what survived underneath the existing images. Furthermore, seeing in finer detail what preparatory sketching was done can lead to questions of if the preparatory drawings survived, and at least with the Ginevra, the fact that the face was pounced and others have found what was supposedly a preparatory drawing for the hands indicates that it may be a connecting piece of the story. But, to paraphrase Dr. Delaney, he is just providing the newest tools and showing what they can do; it’s up to the historians to make use of it all.

by Roy Williams
directed by Leah C. Gardiner

Showtimes: 8pm on weekdays, 2pm matinee and 7pm show on weekends

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The Folger presents The Gaming Table,  by Susanna Centlivre.

Ticket prices: $30-65

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Running until 3/4, $8 entry into the exhibit hall.

Click for more information on the NatGeo Museum’s exhibit of the Anglo-Saxon Hoard.