This is the picture I really wanted from Yellowstone. An eye-level shot of a snow-covered bison plus a beautiful background. Unfortunately, due to the limitations of the laws of optics (i.e. the laws of physics), it's not possible to use a 560mm focal length lens and to largely fill the frame with the subject while, at the same time, rendering the background sharply focused. We never see out of focus background with our eyes. That is a manmade construct. So, to create what I wanted, I put two pictures together: the snowy landscape and the bison. My camera settings for the bison shot were 1/800, f/16, and 1600 ISO, and my lens combination was a 100-400mm Canon lens with a 1.4x teleconverter. Note that the best case scenario for a winter landscape is when the trees are laden with snow just after a snowstorm and before the wind blows the snow off the trees or the temperature rises and the snow melts.