I was sitting at a wedding and talking to a friend animatedly. The camera flew out of my hand and landed lens first and then fell on it's body. My concern is that I messed up the AF or the IS. How can I test that both are working okay? If they are not functioning correctly, what are some recommendations to fix it? The lens is a Canon 24-105 4L. Thank you for your attention.

  • Does it still take pictures correctly? – user13451 Sep 15 '14 at 3:50
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    I'd be more concerned about the alignment of the mount flange and the lens elements than about IS or AF. – Michael C Sep 15 '14 at 4:37

Take some pictures!

Using Auto Focus, are the images in focus? Is the point of focus the same distance from the camera on each side of the frame? On the top and bottom? I would be more concerned about the lens mount flange remaining parallel to the sensor. Test this by taking the fastest lens (widest aperture) you have and shoot a flat surface such as a wall with the camera parallel and the optical axis perpendicular to it. Is the plane of focus flat? Use manual AF point selection to verify that each focus point is operating correctly.

Use slower shutter speeds and see if the IS functions as it should. You should be able to get about three stops slower than the 1/focal length rule before you see camera shake when the IS is active.


Take a photo (with AF) of something flat and fairly regular (like a brick wall) that is parallel to the camera sensor at your normal working distance.

If the entire image is soft or if some corners are noticeable softer than the other corners (there is always some variation, only worry if the difference is big enough to be noticeable at normal viewing condition, not at 100% zoom) you knocked something out of alignment and you should get your lens to a service center.

There are ways to diagnose what went wrong but it doesn't really matter because the only solution to all those problems is to take the lens to someone who can recalibrate it.

Update: as Michael Clark correctly commented things in the camera body can also be knocked out of alignment, so you should repeat the test with another un-dropped lens to see if the problem is in the body or the lens - or just take both to be serviced

  • Alignment problems could also be caused by misalignment of the mounting flange on the camera. I've known of several cases of this that were caused by drops. – Michael C Sep 16 '14 at 1:25

The other answers are very good ways of determining if the camera is in need of immediate servicing, but my advice is to just take the camera and lens in for servicing.

My rationale is that, even if you determine that you were lucky this time, and everything seems to be in order, one day down the road the camera will start flaking out, or it will damage a different lens, or some other vaguely undefined behaviour will crop up.

So, if you need this camera to work at an event, or on vacation, or some other place where replacement and/or troubleshooting is going to be a problem, invest in the piece of mind to get the rig certified. Assuming the rig is worth the investment (and I assume it is.)

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