These controls let you add depth of field to the rendering. Depth of field is available only when you render a Camera or Perspective view.
When on, the rendering generates depth of field. Default=off.
When From Camera (the default) is chosen, the Quicksilver renderer uses the camera's Target Distance and f-Stop settings to generate depth of field. You must choose Depth Of Field (mental ray/iray) as the camera effect, and turn on Enable to make it active.
When Override Camera is chosen, you can choose values for generating depth of field that differ from the Camera settings.