Running Golden Retriever Picture
A Golden Retreiver runs at full speed in the shallow snow. If your subject is moving toward or away from you, AI Servo AF mode is usually necessary to keep the subject in focus. And if the subject is moving fast, a short shutter speed is another requirement (to prevent motion blur). The late day sun was very helpful with the latter requirement in this shot.
Camera and Lens Settings
300mm f/4.5 1/2000s ISO 160 4896 x 3264px