I am moving from my dedicated video camera to my Nikon D610. but i am having a heck of a time figuring out the focus.

For example if a subject is standing 10 feet away and they start to walk across the frame do i need to keep pushing the shutter halfway to refocus? Isnt it suppose to automatically follow the subject and keep them in focus?

I cant for the life of me figure out how to get this thing to focus when moving it without pushing the shutter halfway down, thus creating a god awlful noise on the video. I have tried AF-A AF-C and AF -S I must not have something right. I am using a TAmron 24-75 2.8 lens.

Thanks in advance for the help..

DSLR's, even with their half-baked "continuous autofocus" modes, will never autofocus quite like a handicam. They're simply different machines, that work differently. Even the best autofocus in this type of camera, which you'll see best implemented in the mirrorless cameras, yields what I would consider unusable focus pulls. They're not smooth, you can't control the speed of the focus, and yes, you will hear the lens motor. Especially with a Tamron.

If you want to pull focus in a scene like you've described, you'll need to do it manually for usable results. It's possible to pull focus with just your hand and the lens, but a follow-focus rig will definitely help (you can mark your pulls on the ring, for example), and there are several economical options available. An external monitor will also improve the process.

DSLR's can produce great video, but you have to work within their limitations. And not having (usable) full time autofocus is one of those limitations.

Brian,
thank you so much for this response. I did some testing with a 50 prime and i see what you mean with the auto focus click, buzz, etc... i dont like it. I do like the quality of the video however.

I also have a sony A6000 that i just love and as you indicated the mirror less does not have all that focus noise. Although i do have a H4N Zoom i would live to have the external mic capability on my A6000

Thanks.. I think you just saved me a bunch of money on a new cine lens for the D610