Because the barrel is heavy enough to overcome its own friction when gravity works along the zoom axis. It is a mechanical property of extending zooms rather than a fault, and some lenses publish a lock for it.
A zoom that slides when the camera hangs muzzle-down is doing something predictable, and the cure is mechanical rather than electronic.
The mechanism
An extending zoom moves a heavy group of glass along the barrel. Friction holds it where you left it; point the lens down and gravity pulls along the same axis. Where the mass exceeds the friction, the barrel extends on its own — most noticeably on long ranges, where the extension and the mass are greatest.
Why the long zooms suffer most
Because they extend furthest. The longest range in this catalogue is a bridge camera printing 20-1200 mm on a single fixed lens, and the extending telephoto zooms here reach 300, 350 and 400 mm — all with substantial barrels.
What helps
A zoom lock, where the maker fits one, which holds the barrel at its shortest for carrying. Otherwise: carry the camera across the body rather than hanging straight down, and support the barrel with a hand when aiming steeply.
What does not help
Stabilisation, which addresses movement during exposure. And a tighter strap, which changes where the camera sits rather than what the barrel does.
What people ask before they commit
Does creep mean the lens is worn out?
Not on its own. Friction in a zoom mechanism is set by design and eases with use, so a lens that creeps after years may simply have loosened into its working state. Grinding, wobble or a barrel that shifts sideways are different symptoms and do point at wear.
Is a zoom lock the same as image stabilisation?
No — they answer unrelated problems. A lock is a mechanical catch that holds the barrel at one length, usually the shortest, for carrying. Stabilisation compensates for camera movement during exposure. A listing that publishes one has said nothing about the other.
Last reviewed 12 September 2026