Fig. 8: Detail of Van Ruytenburch’s doublet sleeve.

a, b Visible light details of the 5 µm resolution photograph. The areas shown in (c) and (d) are both shown as white boxes in (b), respectively. e The reflectance spectra from the yellow ocher dots indicated with white arrows in (c, d). f Example of a brightness simultaneous contrast illusion (g) Example of a color simultaneous contrast illusion.