There are just too many buttons to push in rapid succession when you separate AF and shutter when the target is moving really fast. Also, when you use the BushHawk, you have no choice. The trigger is basically a cable release. There is no way you can AF-ON and operate the trigger to capture an image. You often have 3-5 seconds of opportunity, and you have to concentrate on focus on the eyes while pulling the trigger...nothing else matters if you have the camera setup properly.