In cinematography, a focus puller or first assistant camera (1 AC) is the member of a film crew responsible for keeping the camera's focus right during a shoot. Often this requires pulling the focus with a follow focus device during the take without looking through the camera (the camera operator is doing that), to compensate for camera or subject movement. The margin for error is often very small, as little as 1/4 or 1/8th of an inch (3 - 6 mm). Most people on the set will agree that the focus puller's job is the most technically difficult of any during production. A film reel unwinding Although literally it means writing the movement, the term cinematography is generally understood as the art and process of recording visual images for the cinema (with a camera) and later developing those images in a laboratory. ... A film crew is a group of people hired by a film company for the purpose of producing a film or motion picture. ... A camera is a device used to take pictures (usually photographs), either singly or in sequence, with or without sound, such as with video cameras. ... The word focus (pl. ... The word focus (pl. ... A follow focus is attached to a film or DV cameras manual servo lens and subsequently onto the body of the camera via a set of rods that are standardized in the film industry. ... This article needs cleanup. ...

To accurately focus on the subject, it's common to measure the distance (usually with a tape measure or, more recently, with electronic tape measures using lasers) between the camera and the subject being focused before the take. Specifically the measurement is from subject to film plane or image sensor, most movie cameras have a little stud even with the film plane where the focus puller will attach his tape measure. Professional 1st AC's have many tricks for pulling focus in difficult situations, such as when accurate measurement is impossible. Self-retracting pocket tape measure A tape measure or measuring tape is a ribbon of cloth, plastic, or metal with linear-measure markings, often in both imperial and metric units. ... A film plane is the area inside any camera where the individual frame of film is positioned during exposure. ... A film plane is the area inside any camera where the individual frame of film is positioned during exposure. ...

The 1st AC is also responsible for maintaining the camera including keeping the lens and film gate clean during filming. They are also responsible for placing filters in the matte box in front of the lens and for being aware of lens flares. The film gate is the square opening in the front of a motion picture camera where the film is exposed to light. ... Photograph of NASA lunar lander containing lens flare Lens flare typically manifests in images or views through optical systems as several starbursts, rings, or spheres arrayed in a sequence across the image or view. ...