Exploring the Limitations and Advantages of Multi-Spectral Imagingin Papyrology: darkened, carbonized, and palimpsest papyri
multi-spectral imaging, graphic user interface, carbonization, papyrus, palimpsestpapyrus, ostraca
MSI involves the capture of multiple images of light reflected off a single target, each image acquired at a different wavelength. Full application of MSI typically spans the wavelength range of ~380 nm to 1100 nm with silicon based cameras. Digital spectral data are acquired for subsequent enhancement of discernible contrast between ink and writing substrate(papyrus, or ceramic, or other material) and, thereby, the legibility of the surviving text.
The ATIG system captures reflected light which is filtered through both narrow and wide band pass filters. Because contrast between surviving ink and papyrus generally peaks outside the visible light spectrum, an image captured beyond 700 nm will render greater legibility than a conventional color or black-and-white image. However, MSI also reveals that relatively narrow filtering (10 – 40 nm bandwidth) can provide better contrast than wide-band IR imaging or simple red-channel capture. Often, widely differing reflectivity of individual documents necessitates comprehension of multiple images at multiple wavelengths for rendering highest possible legibility for each text’s singularly compromised areas.
Collating images in varied wavelengths affords examination for optimal legibility on various textual areas. And composite images can be useful. A scholar might use a graphic user interface to isolate, combine, and eliminate constituent images, adjusting the wavelength to fine-tune the legibility of each textual obstacle the user deciphers. Now it is developed, ourGUI simplifies viewing the image cube and allows real-time interaction with the full data set.
This paper argues for the application of multi-spectral imaging and presents findings from ongoing imaging projects. These several projects demonstrate that inks and substrates reflect and absorb light differently and manifest variegated results in different wavelengths of light.Consequently, the more flexible an imaging technique can be, the more likely the unique characteristics of a given text can be captured and studied.
A recently published argument promoted broadband monospectral infrared imaging in papyrology advocating that method of infrared digital imaging against multi-spectral imaging (Bülow-Jacobsen 2008), the authors responded by explaining more clearly the multi-spectral imaging process, by discussing in what situations MSI might be preferable to mono spectral imaging, and by reporting recent image processing developments made by the Ancient Textual Imaging Group (ATIG) at Brigham Young University (Bay et al., 2010). This paper is largely based upon that response.
Original Publication Citation
“Exploring the Limitations and Advantages of Multi-Spectral Imaging in Papyrology: darkened, carbonized, and palimpsest papyri.” Pages 87–97, Digital Imaging of Ancient Textual Heritage: Technological Challenges and Solutions. Proceedings of the Εἰκονονοποιὶα Conference 28–29 October 2010, Helsinki Finland. Roger T. Macfarlane, Thomas Wayment, Stephen M. Bay, and Gregory Bearman.
BYU ScholarsArchive Citation
Macfarlane, Roger T.; Wayment, Thomas A.; Bay, Stephen M.; and Bearman, Gregory, "Exploring the Limitations and Advantages of Multi-Spectral Imagingin Papyrology: darkened, carbonized, and palimpsest papyri" (2010). Faculty Publications. 3666.