Rotating lens turret on film cameras — three or four lenses on one axis for quick swaps in the field. Built-in lens magazine, mechanical and reliable.
You'll primarily encounter the lens turret in archival footage or when working with older 16mm cameras — a rotating mount on which three to four lenses are simultaneously attached. Instead of unscrewing the entire lens and attaching a new one each time, you simply rotate the turret nose to the next position. On set, this saves precious seconds when a scene is rolling and you need to quickly change focal length without lowering the camera.
Practically, it works like this: The mount is directly on the camera body, usually with four positions (often 12mm, 25mm, 50mm, 75mm, or similar standard focal lengths). A snap mechanism or a detent system precisely locks each lens into the optical axis. The big advantage was speed — especially in documentary filmmaking or run-and-gun shoots when you didn't have time to change lenses. It was also standard for newsreel shooting in the 1950s–70s. The disadvantage: You are limited to the focal lengths that are mounted. Modern zooms make this completely obsolete.
What you should still know today: The turret creates optical characteristics that some DPs deliberately use. The lens quality was often not the same across all four positions — an old Arriflex 16 with a worn turret is immediately noticeable when you change settings. Some cameras (especially Soviet cameras like the Krasnogorsk) still have functional turret designs today that are very reliable. So, if you want to shoot in vintage format or aim for a found footage aesthetic, an old turret camera body can certainly be a statement — not out of technical necessity, but for optical intent.
Important: Always readjust focus before changing, as each lens on the turret can have minimally different positions. You no longer need this in the digital age, but anyone working with film or old cameras should keep this in mind.