Fig. 4
From: Reconstructing Van Gogh’s palette to determine the optical characteristics of his paints
Estimation of K&S values for pigments zinc white and bone black. a Reflectance curves as measured over black (dashed lines) and over white substrate (solid lines), where percentages refer to concentrations of bone black. These are compared to Kubelka–Munk predictions for the various mixtures, both over black (open markers) and over white substrate (filled markers). b Optimized values for K and S parameters