Livingstone's 1871 Field Diary

A Multispectral Critical Edition

Spectral Imaging in Scotland
Spectral imaging, when used for the study of cultural objects, involves illuminating an object with successive wavelengths of light – starting with ultraviolet, working through the visible spectrum, and concluding with infrared – then digitally photographing the resulting illuminations. The produced images all have exactly the same pixel dimensions, and are spatially registered, the content being equivalent at each pixel location in each image. Later, imaging scientists process this data in order to enhance select features of the cultural object.
Visit the related section from Livingstone’s Letter from Bambarre.
Figures 1, 2, 3, 4, 5, 6. A page of Livingstone's 1871
Field Diary under six of the twelve illuminations used.
Imaging Set-Up
The Livingstone team spectrally imaged the 1871 Field Diary in the Reprographics Studio at the National Library of Scotland (NLS). The NLS could only allocate about half of the Studio to the team due to the need to support other ongoing activities. As a result, the team created a dark room by purchasing window curtain "blackout" lining at a local store and then hanging this curtain over the opening between the two halves of the Reprographics Studio, an expedient that worked surprisingly well. The NLS also provided the copy stand upon which all Livingstone folia were placed for imaging, tripods for the lighting system, a computer monitor for the camera system, and two workstations for the individuals operating the camera system and data logger.
Figure 7. Members of the Livingstone team (from left, Boydston, Toth, Christens-Barry, Simpson) moments before initial imaging. The edge of
the copy-stand is just visible in the foreground left. The "blackout"
lining curtain, partly pulled up, appears in the background.
The Livingstone team transported the EurekaVision™ spectral imaging system from the U.S. and set up the system during the first two days of the imaging sessions. The EurekaVision™ system, a state-of-the-art image capture system, maximizes the information recorded with minimum impact on the historical documents. MegaVision’s PhotoShoot™, the software that powers the system, is designed to ease user tasks such as image sequence setup, imaging parameter entry, focus and image inspection, collection and organization of metadata, and image conversion and storage.
Figures 8, 9. Left: Wisnicki and Harrison discuss the 1871 Field Diary.
The MegaVision E6 39 megapixel camera hangs overheard. Right: Karen
Carruthers (Property Manager, DLC), foreground, examines a leaf
of the manuscript; Boydston operates the workstation in the background.
The components transported by the team to Edinburgh included:
1) monochrome MegaVision E6 39 megapixel camera back (7216 X 5412 pixels; 16-bit data with approximately 12 bits of dynamic range) mounted in a technical view camera with a 60mm UV-VIS-IR lens and a color filter wheel installed for UV fluorescence studies.
2) light-emitting diode (LED) illumination panels which were placed on tripods on either side of the copy stand in symmetric downward-looking positions angled approximately 45º on either side. The team also used diffusers to create uniform and nondirectional light fields. Raking illumination was provided in two spectral bands from either side of the manuscript.
3) modified desktop computer that controlled the imaging system using MegaVision’s PhotoShoot™ 4.0 software. This software orchestrated the operation of both camera and lighting through FireWire and USB connections, respectively.
Figures 10, 11. The LED illumination panels.
Each LED panel contains seven banks of LEDs that emit in the ultraviolet (1 wavelength) and visible regions (6 wavelengths) of the spectrum and five additional clusters of LEDs that emit in the infrared region (5 wavelengths). The geometry of the LED light panels is designed to provide maximum uniformity of the illumination at the surface of a leaf being imaged. A primary advantage of the system is that LEDs do not generate heat that can damage fragile pages. In addition, illumination from a low “raking” angle enhances the visibility of surface height variation, yielding images in which impressions or surface relief features are enhanced.
The EurekaVision™ system illuminated each Livingstone folio with twelve bands of wavelengths of light from the ultraviolet (UV) through the visible and the infrared (IR):
Band = Wavelength in nanometers
01 = 365 (UV) 07 = 638
02 = 450 08 = 700 (near IR)
03 = 465 09 = 735 (near IR)
04 = 505 10 = 780 (near IR)
05 = 535 11 = 850 (near IR)
06 = 592 12 = 940 (near IR)
The monochrome camera automatically photographed the folio under each illumination, with the raw image data stored on an external hard drive attached to the desktop computer. In addition, the team used four raking lights (lights that illuminate the folia at an oblique angle and so highlight page topography) mounted within separate panels and on separate tripods when imaging folia that had not been laminated, as follows:
Band = Wavelength in nanometers
13 = 940RR (IR raking right)
14 = 465RR (blue raking right)
15 = 940RL (IR raking left)
16 = 465RL (blue raking left)
The team chose to use a monochrome camera, without color or infrared filters, because doing so allows: 1) lower light levels for illumination, 2) no interpolation or preprocessing of the filtered image, minimizing collection artifacts, and 3) unfiltered light from all spectral bands to reach the camera sensor. Such a camera yields very pure, high-resolution, registered images of each spectral band and facilitates processing not only for text enhancement, but also for very accurate color reproduction.
Data Logging, Collection, and Copying
The camera operator and the data logger collaborated in running the EurekaVision™ system, while a representative of the NLS or the NTS handled the primary documents and set and flipped them on the copy stand. A variety of locally-recruited personnel took part in the camera operation and data logging, including Anne Martin (DLC), Karen Carruthers (DLC), Suzanne Lamb (NTS), Alison Metcalfe (NLS), and Kate Simpson (Edinburgh Napier University). Several Livingstone team members also actively participated. The process required constant rotation of personnel due to the long hours, continuous concentration required, and complexity of the data to be logged.
Figures 12, 13. Left: Toth trains Simpson in data logging.
Right: Simpson trains Anne Martin (Archivist, DLC).
To ensure the team captured accurate metadata about the objects and images, Data Manager Emery developed the Multispectral Imaging Metadata Machine, or MSIMM (pronounced "Miss M."), which powered data logging. As each document came up for imaging, the data logger located the document in the MSIMM database and read off the file name to the system operator who entered it into MegaVision’s PhotoShoot™. The data logger, in turn, noted any unusual features of the document or exceptional imaging circumstances (such as a reshoot due to previous interruptions) in the log. Once data had been entered, all personnel put on UV protective glasses, turned off the room lights, and the capture of the image set began. Each capture lasted about two minutes, with times slightly extended when raking lights were used. During capture no one could pass through the dark room because the data could be compromised and because individuals without appropriate eye protection could be injured by UV light.
Figure 14. During a break from logging, Suzanne Lamb (Conservator, NTS) and Karen Carruthers (Property Manager, DLC) examine an unmarked copy of the 24 November 1869 issue of The Standard held by the NLS.
The desktop computer powering the imaging system also collected the raw image data to an external hard drive. For each image, the system produced an image set of either twelve registered images or sixteen if the raking lights were used. Periodically, team members replaced the hard drive containing the raw data and took it away for copying, a task which constituted a full-time job in itself. Team members copied the raw data to other external hard drives brought by the team and transferred files externally via FTP overnight to a designated site. This distribution strategy helped prevent the loss of data and made the data available to scientists onsite (Easton, Christens-Barry) and overseas in Hawaii (Knox) for validation, assessment, and initial processing. The strategy also enabled Emery to review the data and metadata for quality and provide updates to the metadata records and software. As a result, the David Livingstone Spectral Imaging Project was able to operate twenty-four hours a day during this period.
Spectral Imaging in Scotland (cont)