Hi, I have been using my Mavic Pro for 18 months now and loving it - but exclusively for still photography. Now a friend has asked that I take a couple of motion shots for a short film he is making. One is the opening shot where the camera has to come in from out at sea to a cave opening on the beach. The other is reverse, where the camera backs up and away from the cave. Now I know how to focus the camera for a still shot, but what happens when the subjects you want in focus go from far away to close as the camera moves in, and the reverse as the camera moves away? What technique should I use to maximise sharpness for both shots?