Getting a high key picture of a shaking horse is not easy. One of the easiest ways to get a high key horse picture is to shoot a back-lit horse in the snow. Then, with a short exposure dialed in to stop the motion, wait for the horse to spontaneously shake. Or simply have the fortune of the horse being in the right position when you and the camera are properly setup to catch the shake.
A 1,200 lb (545kg) animal violently shaking (at about the frequency we shiver at) is quite impressive – and much more so to a rider fortunate enough to experience the event from the saddle.
I framed the shot too close to the mouth in-camera, but since the background was pure white, it was very easy to add white space on the right side by extending the canvas.