1. A method for determining a sharp panoramic image layer constructed from a group of projection images, the method comprising at least following steps: defining the structure of the panoramic image by at least two crucial parameters, the first parameter relating to the central surface S of the sharp layer and the second parameter relating to the thickness t(s) of the sharp layer, using a penalty function F(S,t) to obtain the best choice for a center surface and thickness function by minimizing said penalty function F(S,t) over parameter space, where said penalty function F(S,t) is F 3 (S,t), and 1) F 3 (S,t) computes first the panoramic image corresponding to the choices S and t(S) given as argument, and penalizes low-frequency images more than high-frequency images of said computed panoramic image.