Although I have already done a focal length comparison from 12mm to 500mm focal length before, I decided to do it once again for telephoto lenses. I receive quite a few emails from our readers, asking about telephoto lenses and focal lengths, specifically whether a focal length of a lens is going to be sufficient for bird and wildlife photography. The below images should give you a pretty good idea about field of view when using particular focal lengths, from 70mm all the way to 1200mm:
The above images are not cropped in post-production and represent equivalent focal lengths relative to 35mm. The longest field of view of the 1200mm shot was captured with the Nikon 200-400mm f/4.0 + TC-20E III TC @ 400mm (800mm effective) on a DX body, which is equivalent to 1200mm. The shortest focal length was captured with the Nikon 70-200mm f/2.8G VR II at 70mm.