Iterative methods showed until now encouraging results to resolve shape from shading. This kind of methods generally work on synthetic images, and occasionally on real images, even if such images do not agree in general with the hypotheses of shape from shading. In this article, we describe the assumptions mentioned above, and propose an original methodology, which enables the production of real images and the process allowing to correct most of their defects in order to make them correspond to most of these assumptions. Moreover, we propose a descent gradient iterative scheme, thanks to which we prove that shape from shading can work as well on real images as on synthetic images.