Most of the time, in the world of bird and wildlife photography, you want the longest telephoto lens you can find. The new Olympus 100-400mm f/5.0-6.3 IS lens has an effective focal length of 200-800mm in a relatively compact, affordable form factor. If you add the M.Zuiko Digital 1.4X Teleconverter MC-14 to the Olympus 100-400mm f/5.0-6.3 IS lens, you get a lens with an EFL of 1120mm. If you add the M.Zuiko Digital 2X Teleconverter MC-20 you get all the way to 1600mm EFL.