Radio-controlled focus system enabling wireless lens focus adjustment with sub-20ms latency and 0.02° motor precision. Allows focus pullers remote operation during crane, Steadicam, and drone shots.
Technical Details
Modern wireless follow focus systems operate with a latency of under 20 milliseconds and offer a resolution of up to 0.02° motor angle precision. The motor drive generates a torque between 0.8 and 3.5 Nm, allowing even stiff cine lenses to be precisely controlled. Transmission is digitally encrypted via proprietary protocols or standardized systems such as RT Motion (RED) or CMotion (ARRI). High-quality systems feature lens mapping functions that can store and recall focus marks with millimeter accuracy.
History & Development
Heden developed the first commercial wireless follow focus system in 1995 for broadcast applications. Preston Cinema Systems established the MDR standard for cinema productions in 2003 with the FIZ system (Focus/Iris/Zoom). In 2012, ARRI revolutionized the market with the Wireless Compact Unit (WCU-4) through intuitive handwheel control and seamless camera integration. Since 2018, systems like the Teradek RT Motion have enabled real-time data transmission with sub-frame accuracy for high-speed shots up to 1,000 fps.
Practical Use in Film
In "1917" (2019), cinematographer Roger Deakins coordinated complex Steadicam sequences across multiple focus pullers using RT Motion systems. Wireless follow focus is indispensable for crane and drone shots – "Skyfall" (2012) utilized Preston systems for the Istanbul motorcycle chase with Technocrane insertions. In confined shooting situations, it allows the 1st AC to operate outside the set boundaries. Disadvantages include radio interference in electromagnetically charged environments and battery dependency for long takes.
Comparison & Alternatives
In contrast to mechanical focus pulling via rods (Follow Focus Rod), wireless follow focus offers unlimited freedom of movement. Wired systems like Preston Light Ranger eliminate radio interference but limit the range to 150 meters. Modern alternatives include AI-based autofocus systems (Canon Dual Pixel CMOS AF) and LiDAR-assisted distance measurement (DJI LiDAR Range Finder). Wireless follow focus remains the standard for professional productions with moving camera systems, while mechanical systems are preferred for static studio setups.