In this contribution we investigate the performance of steerable functions to characterize keypoints. Steerable functions were introduced recently by Perona as an efficient method to calculate the response of a filter in a continuum of orientations, scales, and other parameters. For the analysis of points with events at multiple orientations, functions with a high orientational resolution are needed. We discuss criteria to judge the quality of a function to serve for orientation analysis. To handle line as well as edge junctions, we use a complex function with the real and imaginary part approximately in quadrature. An associated one- sided function allows to distinguish between terminating and nonterminating edges and lines. To analyze thick lines and blurred edges the function is also steered in scale.
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