Why does my stabilized zoom lens jolt at one focal length when powered on?
Asked 5/6/2015
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2 answers
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My Sigma 18-50mm f/2.8-4.5 shows a sudden image shake and visible front-element jolt only when I zoom past about 24mm. It happens when the lens is mounted on the camera and powered on, but not when the camera is off or when the lens is off the body. The AF/MF and stabilization switches do not seem to change it. Is this likely a normal stabilization behavior, or does it point to a fault in the lens?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
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It's hard to say for sure, but if the issue only appears when the lens is mounted on the camera and when it's powered on, it does suggest that the issue is something to do with the electrics in the lens. Have you confirmed that the issue is still occurring with the lens on another camera body? If so, does the speed at which you zoom make any difference - e.g. if you zoom in/out very, very slowly, does the jolt still happen? What about zooming with the camera held in different positions to see if gravity plays a role? Anyhow, if the problem is still present then it suggests an electrical fault in the lens, and my bet is on a ribbon cable with a crack in it.
Originally by user38928. Source · Licensed CC BY-SA 4.0
user38928
11y ago
0
Generated from our catalog & community — verify before relying on it.
Because it only happens when the lens is mounted and powered, this is unlikely to be normal mechanical zoom action alone. It points more toward an electrical issue inside the lens than simple wear in the zoom mechanism.
A plausible cause is a failing flexible ribbon cable or related internal connection that is affected at a specific zoom position. As the lens moves through that focal length, the cable may flex just enough to momentarily interrupt or disturb communication/power, causing the visible jolt.
A few useful checks:
- Try the lens on another compatible camera body.
- Zoom very slowly and then more quickly to see whether the behavior changes.
- Test with the camera in different orientations in case position affects it.
If the symptom stays tied to that focal length, it suggests an internal lens fault rather than normal image stabilization operation. It may continue working for now, but it could worsen over time. If it matters for reliability, the lens should be inspected or serviced.
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