Focusringen

Focusringen refers to the ring on a camera lens or other optical devices that is rotated to adjust the focus manually. It is a central component of the focusing system and is usually located on the lens barrel near the base of the front element, though its position varies by design.

Turning the focusringen moves the lens elements along the optical axis to bring subject matter into sharp focus. In most still photography lenses, the ring controls a mechanical linkage that directly moves the internal element assembly. In modern autofocus lenses, the ring may be decoupled when AF is active or operate via a focus-by-wire system driven by electronic signals.

Cinema lenses often feature larger, heavily knurled focusringen with a long throw to allow precise and repeatable focus pulls. They commonly include a depth-of-field scale (in meters and feet) and distance markings. The quality of the focusringen affects tactile feedback, gearing, and the ability to hold focus during camera movement.

Beyond photography, focusringen also appears on other optical instruments such as microscopes and telescopes, where it is used to adjust the focal plane to the observer's eye or sensor. In these contexts, the focusringen may be paired with coarse and fine adjustment controls or a separate fine-thread mechanism.