Fig. 2

Comparison between spectra of VNIR hyperspectral imaging and signal of classical RGB camera for typical rock painting pigments. The high-resolution reflectance spectra measured on a very thin layer of red ‘Beauregard’ pigment (red) painted on a carbonate rock, and the non-painted rock itself (brown) are plotted with a continuous line (left scale) [50]. The large dots are simulations corresponding to the RGB signal of a digital camera (Canon 20D, [31]) extracted from these spectra by convolving them with its filter band passes (dotted lines at the bottom, right scale) with ‘error bars’ representing the full width at half maximum of the three filters. The bottom black curve is the total photopic eye sensitivity [26]