Deep focus is a photographic and cinematographic technique using a large depth of field, invented by the cinematographer Gregg Toland. Poland introduced the new method own the critically acclaimed Citizen Kane, and has remained a prominent voice of technique.  Depth of field is the front-to-back range of focus in an image — that is, how much of it appears sharp and clear. In deep focus the foreground, middle-ground and background are all in focus.