Thursday, October 08, 2015

Destroying a Manuscript to Test Multispectral Imaging

Image setup for the experiment.
There is a fascinating new article out today in the journal Digital Scholarship in the Humanities (more on which later) on multispectral imaging (MSI). What makes this article so interesting is that the authors destroyed a manuscript in order to systematically put MSI through its paces.

Here is how the authors sum up their aim (my emphasis):
Previous multispectral imaging capture projects, applied to specific examples of texts of historical importance, have concentrated on recording documents in their current state (generally once important features are illegible). Here, we investigate best practice in the multispectral imaging of heritage material by imaging a parchment document before and after a series of degradation processes, allowing us to assess the effectiveness of image processing algorithms to recover information from degraded documents. This gives us a unique platform for evaluating the quality of recovered images, and allows us to assess the performance of image processing algorithms for analysis of these images.
In other words, the authors applied MSI to a manuscript with no damage, then systematically destroyed the manuscript in various ways only to re-apply MSI so that they would have a more objective measure of best practices. The unlucky specimen is described thus:
The document was an assignment of property which had been deemed to hold no historical or scholarly value, and had been de-accessioned from their collection prior to our request for parchment material in accordance with The National Archives guidance on deaccessioning and disposal.
The unlucky specimen here showing the samples.
From this manuscript the authors cut 23 specimens, all with text and generally avoiding folds and blemishes. Various “degradations” were then applied to 20 of these, ranging from problems in the manufacture, use, and storage of the parchment. This included anything from scraping the ink off to oil stains, chemical reagents, fire, water, smoke, and, yes, human blood (full list here). The specimens were then photographed under the same conditions both before and after the damage was done. In total, they took 2,800 images!

The blood sample before damage (left), after (center), and the best result from MSI (right).
Naturally, they found that MSI had different levels of success with generally more success.
In some samples in which the writing has been rendered unreadable by the treatment, the writing can be recovered, including aniline dye, oil, and blood. In some samples the writing is completely obscured or the parchment has been severely affected and recovery is all but impossible, including iron gall ink, India ink, and mould. In most cases, however, the image processing algorithms can extract more information from the multispectral images of treated samples corresponding to the writing than the human eye can see.
The real value of the study, of course, lies in the ability to measure the relative success and to isolate the specific circumstances in each case. They don’t give all the results in the paper (they do elsewhere) and they are clear that this is not a systematic study of any one type of damage (although they hope to in later studies).

This method raises questions about when to destroy the past in order to better understand it, but I’ll leave those issues for you all to discuss. For my part, I would have liked to know a little bit more about how this document was “deemed to hold no historical or scholarly value.” Apparently there exist guidelines for just such a decision.

I’ve never been involved in the direct process of applying MSI, but I imagine this study would be very useful to those weighing the cost benefit of using MSI.

You can read the whole article online (free).

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