Focus puller topic

In cinematography, a focus puller or first assistant camera (1st AC) is the member of a film crew responsible for keeping the camera's focus at the proper position during a shoot. This typically requires pulling the focus with a follow focus device during the take, to compensate for camera and/or subject movement. This requires intimate knowledge and experience with the optical principle of depth of field, which the 1st AC must learn to exploit to his or her advantage. In extreme circumstances... full article at wikipedia