In the Chile side of Patagonia, in Torres del Paine National Park, I hired a tracker to locate wild pumas -- mountain lions. We were lucky enough to find this mother with a large cub. The youngster wanted to play, as you can see here, but that created a problem for the mother who was intent on hunting. I used a tripod for this shot, and my lens arrangement was a Canon 500mm f/4 telephoto plus a 2x teleconverter, giving me 1000mm of focal length. Because I was using an f/4 lens, the AF function worked fine. Had I been using a lens with a maximum aperture f/4.5 or smaller, I would have had to manual focus the lens because the teleconverter reduced the light entering the camera by 2 f/stops. My settings were 1/640, f/8, and 1600 ISO. I cropped this image about 30% because the cats were pretty far away.