I photographed this sidewinder snake on a dune in Namibia. It is venomous, and it can move across the sand at an astonishing 18 miles an hour -- faster than I can run! It was difficult to capture in a still image because of its movement, but I was able to get three pictures and then it was gone. Believe it or not, I used a 24 - 105mm lens set to the 105mm focal length. It's the pattern in the sand that makes this work so well. My settings were 1/320, f/14, and 400 ISO. I used a decent amount of depth of field because the surface of the sand was oblique to the plane of the camera back (i.e. the plane of the digital sensor). That meant that depth of field would have been a problem with a large aperture.