Remote-controlled servo motor for precise lens focus adjustment, delivering 0.8–2.4 Nm torque. Enables rack-focus movements in 0.3 seconds with wireless range up to 1000 meters.
Technical Details
Focus bugs operate with servo motors that generate torques of 0.8-2.4 Nm and enable speeds of 0.01-360 degrees/second. For example, the Preston HU3 Wireless System achieves a latency of under 8 milliseconds with a wireless range of up to 1000 meters. Mounting is done via standardized 15mm rods or directly via lens support systems. Modern variants like the Teradek RT integrate digital encoders with 16-bit resolution for reproducible focus points.
History & Development
In 1987, Preston Cinema Systems developed the first commercial focus bug for the film production "Empire of the Sun." The analog systems of the 1990s still worked with potentiometers and only achieved 8-bit resolution. In 2003, Cinematography Electronics introduced the CineTape, which combined ultrasonic distance measurement with focus bugs. Since 2010, digital systems with tablet integration and GPS-assisted calibration have dominated the market.
Practical Application in Film
For "Blade Runner 2049," Roger Deakins used RT Motion systems for complex rack focus movements between foreground and background. Focus bugs enable rack focus speeds of 0.3 seconds between focus points with 85mm lenses. Steadicam operators utilize wireless systems because traditional follow focus wheels are mechanically inaccessible. In combination with zoom motors, precise parfocal movements are created that would be impossible manually.
Comparison & Alternatives
Traditional follow focus systems offer haptic feedback but require direct access to the lens. Wireless Follow Focus (WFF) is increasingly replacing wired focus bugs, while force feedback systems like the Preston Light Ranger combine the advantages of both worlds. Autofocus systems in modern cameras achieve higher speeds but do not offer the narrative control of manual focus pulls for cinematic imagery.