## 3 EM Techniques for CH Diagnosis
### Multispectral and Hyperspectral Imaging
Licensed under Creative Commons [[http://creativecommons.org/licenses/by/2.0](http://creativecommons.org/licenses/by/2.0)]([http://creativecommons.org/licenses/by/2.0](http://creativecommons.org/licenses/by/2.0)) (accessed on 20 November 2024), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. No changes were made to the figure, but to capture. et al., not as accurate as those produced by HSI or spectrophotometers. The advantages of HSI over MSI are also emphasized by [PERSON] et al., who claim that with the transition from multispectral to hyperspectral imaging, new applicative perspectives in CH scenarios have become possible. \"HSI enables the acquisition of a dataset that includes hundreds of spectral images acquired in very narrow spectral bands (bandwidth 2-10 nm). These data allow the reconstruction of a reflectance spectrum at each pixel in the scene\" [113] (p. 2). HSI applications range from large painted surfaces to small and detailed art objects. Recently, near-infrared (NIR) hyperspectral techniques--used to identify materials employed by the artist [114]--have been coupled with X-ray fluorescence (XRF). This combination of techniques provides a robust distribution of pigments [100]. Jet materials and pigments are often in many paintings \"mixed intimately, resulting in light that does not simply reflect off one material [...] but instead is reflected and/or absorbed by the other adjacent material (i.e., scattering) before entering the camera. Consequently, the measured spectrum is not, in general, a weighted linear sum\" ([115], p. 2). This means that classification and labeling remain challenging. While neural networks may offer assistance, according to [PERSON] et al., existing spectral datasets are small and do not reflect the vast diversity characterizing painted cultural heritage (CH) objects. However, based on the literature reviewed, paints are the most emphasized field in the application of scientific techniques to CH. Hyperspectral Imaging (HSI) is better suited for Spectral Mixture Analysis than Multispectral Imaging (MSI) due to its higher spectral resolution. Standardization initiatives are progressing to improve the consistency, accuracy, and reproducibility of MSI in CH applications. A summary of the key efforts is provided in Table 9. \begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt}} \hline \hline \multirow{2}{*}{Development of Standardized Protocols} & ISO (International Organization for Standardization) and ASTM (American Society for Testing and Materials) are developing guidelines for CH imaging. ISO 23745 sets standards for digital artwork imaging, focusing on calibration, lighting, and documentation. \\ \hline \multirow{2}{*}{Calibration Procedures} & Establishing strict calibration protocols, like using certified standards and consistent lighting, is essential for reliable, comparable MSI data. \\ \hline \multirow{4}{*}{Metadata and Documentation Standards} & Creating metadata schemas (e.g., Dublin Core, CIDOC Conceptual Reference Model (CRM)) records imaging details, settings, and processing steps, improving repeatability and data sharing. \\ \cline{2-3}  & Inter-Calibration Campaigns and Reference Materials and promote best practices. \\ \hline \multirow{2}{*}{Software and Data Processing Transparency} & Encouraging open-source pipelines, detailed documentation, and standardized data formats enhances reproducibility and data sharing. \\ \hline \multirow{2}{*}{Best Practice Guidelines} & Research groups recommend standardized imaging setups: consistent illumination, fixed camera settings, and controlled environments. \\ \hline \multirow{4}{*}{Emerging Initiatives} & Minimal information for chemosensitivity assays (MICHA) aims to develop shared databases, standards, and best practices for consistency in multispectral imaging of cultural heritage \\ \cline{2-3}  & \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Summary of MSI Standardization Initiatives for CH Applications.