Mechanical gear system for precise remote control of lens focus, typically using a whip and follow focus wheel with a flexible gear ring.
Technical Details
Standard follow focus systems operate with 15mm or 19mm rod systems and offer gear ratios between 1:1 and 1:3. The control wheel typically has a diameter of 100-120mm and features interchangeable focus discs with markings at 5° or 10° increments. Professional systems like the Arri WCU-4 achieve positional accuracy of ±0.02mm. Wireless variants operate on 2.4GHz with latency under 20ms and ranges up to 1000m. Motor follow focus systems generate torques between 0.5-3.0 Nm at speeds of 0.1-360°/s.
History & Development
Mechanical follow focus evolved in the 1920s out of the need for precise focusing with longer focal lengths. Arri introduced the first standardized system with 15mm rods in 1975. In 2008, Preston Systems revolutionized wireless follow focus with the HU3. RED established integrated motor follow focus solutions in 2010 with the DSMC system. Modern systems like the Tilta Nucleus-M (2018) combine wireless control with smartphone apps and cost under 1,500 Euros.
Practical Use in Film
In "Children of Men" (2006), wireless follow focus enabled the famous long takes with precise focus shifts between foreground and background. Cinematographer Emmanuel Lubezki relied on custom Preston systems with three synchronized motors. For Steadicam shots, focus pullers work with distance meters: the standard is the Cine Tape from Aaton with ±2cm accuracy up to 30m. Documentaries often use single-operator systems like the DJI Focus Pro with handle integration. Focus marking is done via A/B points on the focus disc, with professionals working with up to eight marks.
Comparison & Alternatives
Autofocus systems like Canon Dual Pixel AF achieve focus speeds of 0.03s but are only suitable for static scenes without creative focus pulls. Manual lens focus without a follow focus limits operation to a 90° rotation angle on the lens itself. Digital focus pulling systems like FIZ (Focus/Iris/Zoom) integrate all lens functions but cost upwards of 15,000 Euros. Split focus systems operate with two independent motors for A/B camera setups during dialogue.