What focus mode should I use when shooting movies with D5100? How do I keep my subject(s) in focus when they are moving? Like my dog running on beach for example? If it's just an interview with someone in chair, OK, but how about when people (or dogs) are moving? Is it the Continuous focus option, same as Continuous focus option for stills? Or is there a special movie focus setting? Thanks.
There are two options when you are in LiveView - AF-S, and AF-F. Depending one what lens I am shooting, and what movement is expected from the subject, that determines which I get the best results from.
If you are moving the camera around, you will probably get the best results from AF-F. If you are still, you may find AF-S works better. Consider your aperture selection also.