Canon EF 24-105mm f/4L IS II is very blurry wide open—defective or normal?

Asked 11/28/2024

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I bought a used Canon EF 24-105mm f/4L IS II USM and it looks unusually soft at f/4, even on a tripod and even with manual focus. Compared at 50mm and f/4 against two other lenses, the 24-105 is much blurrier. The blur also looks directional, and the direction changes when I rotate the camera, while stopping down to f/8 makes it look much better. Turning IS off and changing shutter speed do not help.

Is this within normal variation for a zoom wide open, or does it suggest a fault? If it is faulty, is there a simple way to confirm it before I use the return/warranty option?

canon decentering sharpness lens-problems 24-105mm

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

balpha

1y ago

2 Answers

That appears to be a pretty bad case of a decentered element.

Here's a simple test using a siemens star; you don't even need to print it, it can be displayed on your monitor.

Originally by Steven Kersting. Source · Licensed CC BY-SA 4.0

Steven Kersting

1y ago

AI Answer

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

This is not normal wide-open softness for that lens. The directional blur you describe, especially changing with camera orientation and improving significantly when stopped down, strongly suggests a lens fault such as a decentered or misaligned element.

A quick way to confirm is to test with a Siemens star or similar focus/sharpness chart displayed on a monitor. If the blur is uneven or directional in a repeatable way, that supports misalignment.

Based on the answers, this is not something to fix with shooting technique or editing, and it is not an acceptable performance tradeoff for that lens. The practical recommendation is to return it or have it repaired under warranty rather than trying to work around it.

Canon EF 24-105mm f/4L IS II is very blurry wide open—defective or normal?

2 Answers

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