DOI: 10.25346/s6lqjm3j
title: Multispectral Imaging (MSI) + Reflectance Transformation Imaging (RTI), December 2024, Biblioteca Capitolare di Verona

description: Dataset Description This Multispectral Imaging (MSI) + Reflectance Transformation Imaging (RTI) dataset originates from the Palimpsests in Danger project. MSI in combination with RTI is applied to palimpsest handwritten codices (manuscripts) from the Biblioteca Capitolare di Verona, which have been previously treated with chemical reagents. This dataset includes multiple high-resolution images taken under varying wavelengths and angles of light with narrowband illumination, high fidelity color RGB images deriving from narrowband visible wavelengths, documenting the manuscripts' historical context and surface details. This enables thorough examination and preservation of the object. Imaging Equipment Description/Specifications A monochrome digital camera, a 120mm Apochromat macro lens, a digital electronic shutter, and a computer-controlled filter wheel are used alongside narrow band illumination sources. Two stationary lights are set at a 45-degree angle to illuminate evenly the object to be photographed. Additionally, and for specific sequence of images, a narrowband light source illuminates the object with direct light from different angles. Color targets, a small reflective calibrated surface (Spectralon) are used to calibrate color, white balance images, and calculate light efficiency. Two small spherical objects are used to record the angle and position of the illumination source by documenting its reflection on the spheres, and assist in production of RTI sets. The specific wavelengths, combination of filter wheels and angle of the illumination source(s) can be determined by records of descriptive filenames. Camera - MegaVision Q15 Camera featuring a dual stage TE cooled CMOS sensor of 150 Megapixel (SONY IMX411BSI back-illuminated sensor). 14192 x 10640-pixel array with 3.76 um pixels. The sensor size is 54 mm x 40 mm and is able to achieve ultra-low levels of dark noise - 1e to 3e. Native 16-bit A/D - 65536 levels. Full Well - 50ke- more than 80ke. Remotely controlled by computer and capturing software. This camera is mounted facing directly down onto the target object and calibration targets. Light sources - 2 x MegaVision Spectra Palette lights housing 18 narrow bands (365nm, 400nm, 420nm, 450nm, 470nm, 505nm, 530nm, 560nm, 590nm, 615nm, 630nm, 655nm, 700nm, 735nm, 780nm, 850nm, 940nm, 1050nm), 2 x MegaVision Auxiliary UV panels (365nm, 385nm, 400nm), 1 x MegaVision LightSheet Panel housing 4 narrowband lights (615nm, 735nm, 940nm, 1050nm), 1 x MegaVision pivoting Arc for RTI 2.44m in diameter (16 White LED lights at 4500K, 20w @ 36V) Lens - MegaVision 120mm f/4.5 Macro UV-IR Apochromat incorporating both floating element and advanced UV-VIS-IR apochromatic color correction technology. Filter wheels - 2 x MegaVision filter wheels housing 3 filters each for a total of 5 filters (R25, G58, B47, R72, 665). Filters R72 and 665, allowed us to experiment with the effect of Infrared Fluorescence. Targets - 1 x X-rite Color Checker Classic, 1 x Macbeth color checker mini, 1 x Spectralon patch of 99% nominal reflectance, 2 x small spherical objects. Software - MegaVision Photoshoot v5 image capture and processing software. Photoshoot communicates with all hardware components, allows the use of predefined and highly configurable image sequence capture, handles metadata, file naming as well as flattening and color creation tasks. Data Structure Data is divided into three main categories and main folders. Accurate_color, Flattened, Processed. The Accurate_color folder includes TIF files of color images for each page of manuscript that was imaged with the MSI equipment. These images are a combination of 9 images captured under narrowband visible wavelengths for each page. The Flattened folder lists subfolders for each of the pages captured with the MSI equipment. Each subfolder includes 19, 40 or 96 monochrome TIF files. Each of these files has been captured with a different combination of lights or filters. Folders with 19 images include a basic set of MSI reflective data, folders with 40 images include a full MSI set (Reflective, Transmissive, Fluorescence, Filtered Fluorescence), while folders with 96 images include the basic set in addition to extra images captured with the object being illuminated only by the light aiming from different angles for every shot, using a pivoting 2.4mm in diameter arc indexed to 7 rotational locations. These later set enables us to experiment with the effect of glossiness and reflections of certain chemical elements and inspect the manuscript page through Reflectance Transformation Imaging (RTI) techniques. The Processed folder lists subfolders for each of the pages captured with the MSI equipment. Each subfolder includes processed files in TIF format. Folder and file names Folder names are composed by the shelfmark (identifier) of the object, the folio/page number, and the description of the technology applied. Example: msXL_222r_MMSI+RTI, msXL is the shelfmark, followed by folio 222r, and finally indicating that MMSI+RTI techniques were used to capture the images of this folder. Followed by a human readable description of the lighting source, specific wavelength, presence of filter (if any), color category of wavelength and a sequential number of the capture order. M = Main Bank, main source of lights illuminating from a 45-degree angle W = Wheel, light sources illuminating from a 45-degree angle, in combination with presence of specific filter in front of the lens element. TX = Transmissive, light source is directly underneath the object illuminating evenly and utilizing transmissive light Arc = Arc RTI, 7 groups of 8 images each. Each group signifies a different pivoted position of the RTI Arc Example: msXL_222r_MMSI+RTI+M0365UV_001, msXL is the shelfmark, 222r is the folio number, MMSI is the capturing technology, M0365UV is the 365 UV light illuminating from the 45-degree main bank light sources, 001 signifies that the image is the first of the imaging sequence. Image Processing Description Software Hoku, ENVI, as well as Photoshop are used to calibrate and process MSI data. The most prominent among the techniques described below is combinations of Principal Components Analysis. PCA: Principal Components Analysis ICA: Independent Components Analysis Date of Captured Data December, 2024 Data Captured by Damianos Kasotakis