Yeah -- I ordered a Helios 58mm at the same time as the Sankor but still waiting for it to arrive from Russia so I can test the system. Good information to know it vignetted with the Canon 50mm because that was my back-up plan! I read the Jupiter 9 is really nice with the Sankor, but again, very long wait times from Russia and hit or miss with the quality. I wonder if the Zeiss Planar 85mm might be a good option with the Sankor...