Abstract: Multi-spectral imaging technique embodiments are presented which involve an active imaging approach that uses wide band illumination of known spectral distributions to obtain multi-spectral reflectance information in the presence of unknown ambient illumination. In general, a reflectance spectral distribution of a captured scene is computed by selecting a number of different illumination spectra and capturing multiple images of the scene. Each of these images is captured when the scene is illuminated by a different one of the selected illumination spectra in addition to the ambient light.