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Fig. 19 a | Heritage Science

Fig. 19 a

From: Analysis of red chalk drawings from the workshop of Giovanni Battista Piranesi using fiber optics reflectance spectroscopy

Fig. 19 aFig. 19 a

Representation of selected original drawings in a PCA score plot matrix that differentiates graduations of red chalk from higher to lesser chromaticity (PC-1) and high to low coverage (PC-2). Drawing 36-18-4 is an outlier, executed on oiled paper. Selected photo macrographs illustrate the appearance of the chalk lines; photographs: Staatliche Kunsthalle Karlsruhe, Maria Krämer. bc (b): FORS reflectance spectra of selected original drawings and drawing mock-ups assigned to different clusters via PCA, and (c) their first derivative

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