Fig. 11
(a) Significant negative correlation between hue angle (h°) and λmax (absorption maximum wavelength): Red-shifted bands correspond to blue-purple coloration. (b) Positive correlations between λmax and both w(Cu) & w(Ca) in Group 3. (c) Inverse relationship between summed band intensities (peak + onset + end, 500–700 nm) and lightness (L*). (d) Correlations between spectral indices (SumG1, SumG2) and chromophore contents. SumG1 = Σ(Maximum, Onset, Endpoint intensities) of 500–700 nm bands (Group 1) vs. w(Mn). SumG2 = Σ(Maximum, Onset, Endpoint intensities) of 500–700 nm bands (Group 2) vs. w(Fe). (e) Relationship between the 500–700 nm band area S and chroma C*. The chroma increases with the 500–700 nm peak area increasing.
