Lambertian reflectance correction for rough and shiny surfaces

For rough and smooth surfaces, there are departures from Lambertian reflectance at the occluding limb. This is due to backscattering from microfacets which protrude above the surface. These departures from Lambertian reflectance limit the applicability of shape-from-shading to the surface. We consider how to reconstruct the Lambertian reflectance component in order to improve the quality of surface normal information recoverable using shape-from-shading. We show that although this correction process is reasonable when the light source and viewing directions are close to one another, it is not applicable when the directions are perpendicular.