Photometric stereo without multiple images

Photometric Stereo (PMS) recovers orientation vectors from a set of graylevel images. Under orthography, when the lights are unknown, and for a single uniform Lambertian surface, one can recover surface normals up to an unknown overall orthogonal transformation. The same situation obtains if, instead of three graylevel images, one uses a single KGB image taken with at least three point or extended colored lights impinging on the surface at once. Then using a robust technique and the constraints among the resulting three effective lighting vectors one can recover effective lights as well as normals, with no unknown rotation.