Technique performed by the 1st AC to shift focus between different subject planes during a take.
Technical Details
Professional cine lenses feature a focus ring with a 300° rotation and linear scaling, unlike photographic lenses with a 90-180° range. Follow focus systems transfer rotational movement via gears (0.8 module) from an external focus wheel to the lens. Motorized systems like Preston FIZ or RT Motion operate with stepper motors, achieving accuracies of ±0.02 mm focus travel. Wireless systems operate on 2.4 GHz with latency below 40ms. The critical depth of field at T2.8 and 50mm focal length is approximately 15cm at a distance of 3m.
History & Development
The systematic application of focus shifts developed in the 1940s with Orson Welles' "Citizen Kane" (1941), where Gregg Toland combined extreme depth of field with selective focus pulls. The term "rack focus" became established in Hollywood in the 1960s. The introduction of the Follow Focus by Arriflex in 1968 professionalized the technique. Digital systems emerged from 2005 with Preston Cinema Systems' HF2 series. Today, systems like cforce mini RF enable focus pulls over distances exceeding 100m with sub-frame accuracy.
Practical Application in Film
In "The Graduate" (1967), Hal Ashby executes focus pulls from Benjamin's head in the foreground to Mrs. Robinson in the background to visualize emotional tension. "Jaws" (1975) uses focus shifts during the "dolly zoom" on the beach. The 1st Assistant Camera (Focus Puller) marks focus points with colored tape on the follow focus and works with tape measure readings. For Steadicam shots, wireless control is used via remote systems. Modern productions increasingly utilize wireless systems with up to three axes (focus/iris/zoom).
Comparison & Alternatives
Pull focus differs from "breathing" (unintended change in field of view during focusing) and "soft focus" (consistently soft image). Alternative methods of directing attention include camera movement, lighting, or composition. Autofocus systems like Dual Pixel AF achieve high speed but offer no creative control over the timing and speed of focus shifts. Deep focus photography deliberately foregoes focus plays in favor of consistent image sharpness.