These tests compare the OOF (out-of-focus) rendering of bright highlight light pinpoints by various lenses. Images are 100% crops from shots taken with my K10D or *ist-D DSLRs of the metal tubes on our dining room chandelier, from a distance of about 15 feet.
IMGP1535 Ultron 40mm f2.8 OOF crop.jpg
IMGP6913 Pentax K85mm f2.8 IF crop.jpg (for reference)