Fig. 2.

Comparison of 35 samples measured through the box (abscissa) and on raw material (ordinate). L*, a*, and b* values are shown in a)-c) and examples of three wavelengths (430 nm, 530 nm, and 600 nm) in d)-f)). Standard deviations resulting from 5 measurements are shown as error bars. In each figure, the solid line is the linear regression model of the dataset, and the dotted line is the 1:1 ratio with a slope of 1. Linear model parameters are given together with r² in the legend on each graph at the bottom right and reported in Table 1.