4 User preference test results The observer data indicates that six of the observers ranked Freemans algorithm as the most preferred of the five tested algorithms. However the other two observers rank Freemans algorithm as the least preferred of all the algorithms…. Freemans algorithm produces prints which are by far the sharpest out of the five algorithms. However, this sharpness comes at a price of artifacts (spurious detail that is not present in the original scene). Apparently the two observers who did not prefer Freemans algorithm had strong objections to the artifacts. The other observers apparently placed high priority on the high level of sharpness in the images created by Freemans algorithm.
Forming an Image Surface (Height Map) Illuminate the surface to get: The shading image is the interaction of the shape of the surface and the illumination Shading Image
Painting the Surface Scene Add a reflectance pattern to the surface. Points inside the squares should reflect less light Image
Problem What if we want to do shape from shading? Need some mechanism of informing the shape from shading algorithm about the reflectance pattern. Image Height Map
Represent Scene As These types of images are known as intrinsic images (Barrow and Tenenbaum) = Shading Image Image Reflectance Image
Not Just for Shape from Shading Ability to reason about shading and reflectance independently is necessary for most image understanding tasks –Material recognition –Image segmentation Intrinsic images are a convenient representation of the scene –Less complex than fully reconstructing the scene