A new 500mm lens for £120? Opteka 500mm f6.3 mirror lens review - YouTube
Amazon.com : Opteka 0.43x High Definition Auto Focus Wide Angle Lens with Macro Attachment for Canon, Fuji, Nikon, Panasonic, Sony and Sigma 58mm Threaded Lenses : Electronics
Making it as a Pro: Lens Review: Opteka 500mm f/8 Mirror Lens