Scene dependence of the non-Gaussian scaling properties of natural images

We report results on the scaling properties of changes in contrast of natur al images in different visual environments. This study confirms the existen ce, in a vast class of images, of a multiplicative process relating the var iations in contrast seen at two different scales, as was found in Turiel et al (Turiel A, Mate G, Parga N and Nadal J-P 1998 Self-Similarity Propertie s of Natural I,Images: Proc. NIPS '97(Cambridge, MA: MIT Press), Turiel A, Mate G, Parga N and Nadal J-P 1998 Phys. Rev. Lett. 80 1098-101). But it al so shows that the scaling exponents are not universal: even if most images follow the same type of statistics, they do it with different values of the distribution parameters. Motivated by these results, we also present the a nalysis of a generative model of images that reproduces those properties an d that has the correct power spectrum. Possible implications for visual pro cessing are also discussed.