Colour statistics of natural and man-made surfaces

The reflectance spectra of natural and man-made surfaces are highly constrained. Statistical analyses have been conducted that confirm that the surface reflectance spectra form a set of band-limited functions with a frequency limit of approximately 0.02 cycles/nm. The reflectance spectra can be represented by a linear-model framework and are adequately described by 6-12 basis functions. However, the spectral properties of surfaces are not so constrained as to allow the human visual system to recover the surface properties from cone excitations. Furthermore, trichromatic colour devices such as scanners and cameras can only capture illumination-specific colour information.