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The authors propose a new photometric stereo (PS) method that augments a conventional four-light approach with coaxial illumination. The new method is based on a four-light, leave-one-out approach: the authors argue that coaxial lighting improves robustness to shadowing and specular highlights. The authors also specify a method to detect pixels that are shadowed or that do not conform to Lambert's law. The approach is tested on cylinders of various materials. The authors found that for dielectrics the method gave reliable results for gradients in the range -2 to 2. The results lead them to conclude that coaxial illumination makes PS more robust to shadow and specularity.