Focus puller

A focus puller or first assistant camera (1st AC) is a member of a film crew's camera department whose primary responsibility is to maintain the camera lens's optical focus on whatever subject or action is being filmed.

"Pulling focus" refers to the act of changing the camera lens's focus distance to a moving subject's distance from the focal plane, or the changing distance between a stationary object and a moving camera. For example, if an actor moves from 8 meters to 3 meters away from the focal plane, the focus puller changes the lens's distance setting in precise relation to the actor's changing position. The focus puller may also shift focus from one subject to another as the shot requires, a process called "rack focusing".