Fig. 8From: Analysis of red chalk drawings from the workshop of Giovanni Battista Piranesi using fiber optics reflectance spectroscopyBox plots of the red chalk types: distribution of the maximum peak positions of the first derivative (left); distribution of the maximum height of the first derivative (right). Box plot features the median line, mean values, and whiskers indicating 1.5 interquartile range (IQR)Back to article page