Follow focus

A follow focus is a focus control mechanism used in filmmaking with film cameras and in television production with professional video cameras. It is ergonomic rather than strictly necessary; in other words it does not contribute to the basic functionality of a camera but instead helps the operator be more efficient and precise. It is usually operated by a focus puller (often called the 1st assistant camera, or 1st AC) but some camera operators prefer to pull their own focus (the act of changing focus is called "pulling" or racking focus).