Is the focus remaining fixed once it is locked onto a subject? i.e. does it track the subject to maintain focus - or if the mavic moves away from a fixed subject will it loose focus? for example, one of the demo shots on a review showed a pull away shot from the top of a small light house. - If the camera was first focused while close to the light house and as the mavic pulls up from it, will the light house and all subjects in similar focal plane become out of focus? ...or will the camera track the lighthouse and keep it in focus all the time?