Canon 24-105L seems soft on EOS 40D — should I send it for calibration?

Asked 11/4/2010

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I’m getting a high percentage of soft images with my Canon EF 24-105mm L on an EOS 40D. Compared with my 50mm and 10-20mm lenses, this lens seems to miss focus more often. I’ve tried different AF points and focus modes, but the issue persists. The 40D does not offer AF microadjustment.

Before I send it in, I plan to do proper tripod-based focus tests. If the lens is front-focusing, back-focusing, or just inconsistent, would Canon calibration likely help? Has anyone seen real improvement after sending in a lens like this for service?

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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Generally, sending in both camera and lens for calibration should result in more accurate AF. I would suggest that you first do some focus tests with batteries or focus charts to determine if the lens is back- or front-focusing, or if it is inconsistent AF (indicating a possible USM issue), that way you can verify the results after the lens comes back from Canon.

Originally by user1868. Source · Licensed CC BY-SA 4.0

user1868

15y ago

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AI Answer

Generated from our catalog & community — verify before relying on it.

Yes—service/calibration can help, but test first so you know what problem you’re dealing with.

Do controlled tripod-based tests with a focus chart or similar target to see whether the lens is:

  • front-focusing
  • back-focusing
  • inconsistently focusing

If it’s a consistent AF error, sending in the camera and lens together is usually best, since Canon can calibrate the AF as a matched pair. If the focus is inconsistent rather than simply shifted, that can point to a lens AF/USM issue.

Also, softness is not always just AF calibration. A lens element can be out of alignment, which can cause softness in certain situations even when focus seems correct. That can happen from a defect or from impact damage, and service can address that as well.

So the sensible order is: test carefully, identify whether it’s focus offset or general optical softness, then send it to Canon or an authorized repair center if the results confirm a problem.

UniqueBot

AI

15y ago

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