How can I troubleshoot a Canon EF 100-400mm lens that suddenly stops focusing and shows erratic IS behavior?
Asked 4/24/2011
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2 answers
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I’m using a Canon EF 100-400mm L IS USM on a Canon EOS 10D. During a soccer match, the lens suddenly stopped focusing and the camera displayed an error. After turning the camera off and remounting the lens, autofocus and image stabilization seemed to work at first, but then the viewfinder image would abruptly shift to one side and pulsate.
The lens has worked fine for years. What basic troubleshooting steps should I try to determine whether the problem is with the lens, the camera body, or the image stabilization system?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
15y ago
2 Answers
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Sounds like a problem with the lens. To confirm, try using the lens on a different camera (perhaps you have a friend you whose camera you could borrow for a few minutes)? If it works fine on other camera, try using a different lens on your camera and see how things are. This should narrow down whether the problem is the lens or the camera.
Try turning off the image stabilization feature and see if the problem continues. It's possible the problem might only be with the IS.
If these things confirm it's a lens problem, you should send the lens to one of Canon's service centers and they can provide an estimate for repair.
Originally by user89. Source · Licensed CC BY-SA 4.0
user89
15y ago
0
Generated from our catalog & community — verify before relying on it.
Start by isolating whether the fault is in the lens, camera body, or IS system.
- Clean the electrical contacts on both the lens and camera body.
- Turn image stabilization off and test again. If the problem stops, the IS system may be the issue.
- Try the lens on another compatible Canon body.
- Try a different lens on your 10D.
These swaps will tell you where the problem is:
- If the 100-400mm misbehaves on another body, the lens likely needs service.
- If another lens also acts up on your 10D, the camera body may be the problem.
- If the issue only appears with IS enabled, the stabilizer is a likely suspect.
Given the sudden autofocus failure, camera error, and shifting/pulsating viewfinder image, this does sound like a hardware fault rather than a user setting issue.
If cleaning contacts and cross-testing don’t resolve it, contact Canon support or send the lens/body to an authorized Canon service center for diagnosis and a repair estimate.
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