The algorithm proposed by Dr. G.D. Finlayson computes the entropy to search the angle of the projection for the intrinsic image. After iterative computing, their algorithm indeed gets the correct angle of the projection, which can be used to compute the intrinsic image. Nevertheless, their algorithm spends a lot of time searching the angle of the projection and doesn’t work well for many other images. In this thesis, Principal Component Analysis, Independent Component Analysis, and Sobel Edge Detection are used to search the correct projection angle for the intrinsic image. In the comparison of the results of the proposed three methods, Sobel Edge Detection can efficiently compute the correct angle of the projection by finding the change of the illuminant. Sobel Edge Detection may not only compute quickly with lighter computational load but also work well for a larger set of images.