This paper presents a framework for the geometric interpretation of a single polarization image taken of specular reflecting objects. The task of recovering 3D shape information of specular objects from intensity images is a difficult if not impossible one, as no intensity-based features are available. Polarization analysis provides additional features to overcome the problem. In particular, the orientation of polarized light is measured, from which constraints on the object surfaces can be deduced. We show how to perform shape analysis from a single polarization image. This new method is applied to local deformation measuring. Along with a discussion of polarization and related geometric issues, algorithms are presented and substantiated by experiments.