Constant point of Focus for DOF?

Hi,
In my “focus” numerical field in my Depth of field post processing puzzle I have a “distance from” puzzle from camera to am empty that’s at the center of my desired object of Focus.

My app’s user’s camera can orbit and pan.

here’s the setup:

Should that setup update constantly to changing camera position? Or do I have to put it in an “every frame do” puzzle?… Can’t seem to tell if it’s working.

should there be an extra multiple factor involved in the distance equation?

Also, can we have more elaboration on the “depth leak” field? Not quite sure what this does.

Thanks!

note: the object fields are text fields because i have a bug where all of my selectors only display “none”. will the text field method work regardless?