A method for image resolution reduction that simulates the reduction of shape resolution and is to be used with shape-from-shading algorithms is presented. Resolution reduction is used for accelerating shape-from-shading algorithms using multiresolution pyramids. The goal of this correspondence is to show that resolution reduction based only on image intensities can be inferior to resolution reduction using knowledge of the surface reflectance. This is true for all cases of parameter estimation from intensity images, when the intensity is not a linear function of the parameters. Since optical reduction of images, as when moving a camera away from the object, is a simple gray-level averaging a question is cast on the general scheme of shape-from-shading. It is concluded that for accurate shape-from-shading one needs to know the distance from the object, and the shape should also be known in advance.>

A method to reduce image resolution that simulates the reduction of shape resolution is presented. Such resolution reduction is critical for shape-from-shading algorithms. This method of resolution reduction is used in accelerating the shape from shading by using small multiresolution pyramids. A Lambertian reflectance model is used, but a similar approach can be developed for other reflectance models. The goal is to show that the resolution reduction based only on image intensities is inferior to resolution reduction using knowledge on the surface reflectance.>