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An observer surrounded by sufficiently small spherical light sources at afixed distance will see a pattern of elliptical images distributed over thesky, owing to the distortion effect (shearing effect) of the spacetime geometryupon light bundles. In lowest non-trivial order with respect to the distance,this pattern is completely determined by the conformal curvature tensor (Weyltensor) at the observation event. In this paper we derive formulas that allowto calculate these distortion patterns in terms of the Newman-Penroseformalism. Then we represent the distortion patterns graphically for all Petrovtypes, and we discuss their dependence on the velocity of the observer.Comment: 22 pages, 8 eps-figures; revised version, parts of Introduction and  Conclusions rewritte

Classification of image distortions in terms of Petrov types