Ronen Basri Weizmann Institute of Science In this talk we will look at shading problems when objects are lit by natural lighting that includes multiple extended light sources. We will begin by asking the question what is the set of images of an object under variable lighting. We will introduce the concept of the illumination cone, which provides a general answer to this question. Next we will use harmonic analysis to show that for lambertian objects the illumination cone is very low dimensional. We will further use this analysis to construct algorithms for recognition and photometric stereo reconstruction. Finally, we will discuss new algorithms for reconstructing the shape of moving objects that account for lighting.