This image was shot in Yellowstone National Park with my Canon 7D and a 150-600 mm zoom set to 150 mm.  The Buffalo was moving alot so I set the camera in shutter priority at 1/2000 sec, upped the ISO to 3200 which gave me an aperture of  f/5.  It was an overcast day.  Post processing was done in Lightroom and Photoshop.