Zoomrings

Zoom rings are the circular controls on photographic and video camera lenses used to change the focal length. Mounted on the lens barrel, the zoom ring rotates to move the internal zoom group, altering magnification and field of view. The ring is typically marked with a focal length scale, such as 24-70mm, and a position indicator for the zoom.

Most consumer and professional zoom lenses couple the zoom ring mechanically to a rotating helical or gear-driven element inside the lens. Turning the ring expands or compresses groups of lens elements, changing the effective focal length. Some lenses use internal zoom mechanisms that keep the overall length stable while the optical group moves; others extend or retract the front element during zoom, a phenomenon known as external zoom.

High-end lenses may provide a parfocal zoom, maintaining focus when switching between focal lengths, which is important in video work. In cinema and some professional stills lenses, the zoom ring is paired with a power-zoom motor and an electronic control, allowing smooth, programmable zoom speeds.

Common design features include textured rubber or metal rings, tactile resistance, end stops at some focal lengths, and sometimes a zoom-lock switch to prevent creep when the lens is pointed downward or stored. Maintenance involves keeping the ring clean and free of grit, and avoiding overtightening.

While broadly similar across brands, zoom rings vary in rotation direction, throw, and damping, reflecting both optical design and user preferences.