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Canon EF 17-40mm f/4L USM

Started Aug 12, 2014 | Questions
KS Chang New Member • Posts: 1
Canon EF 17-40mm f/4L USM

I had EF 17-40mm f/4L USM with my Rebel XSi for few years.  It worked great.  However, it stucks/jams after taking the first photo when I put it on a brand-new 5D Mark II. Why is it doing that?  Is it the lens or camera problem?

Note: My 5D Mark II is brand-new. It works flawlessly with all other EF lens.

(unknown member) Contributing Member • Posts: 650
Re: Canon EF 17-40mm f/4L USM

KS Chang wrote:

I had EF 17-40mm f/4L USM with my Rebel XSi for few years. It worked great. However, it stucks/jams after taking the first photo when I put it on a brand-new 5D Mark II. Why is it doing that? Is it the lens or camera problem?

Note: My 5D Mark II is brand-new. It works flawlessly with all other EF lens.

I would suggest to check if the aperture is working. Set the camera to AV mode, select the smallest aperture f/22, look at the lens from the front side and press the stop-down bottom. The aperture blades should move. If the do not move or move slow or irregular, this might cause the camera to jam.

The aperture blades can get sticky. They should be smooth and clean, free of any lubricant, but mechanical oil from other parts of the lens might get in the way and prevent them from moving freely. At least this is what I saw in some old(er) lenses that were sold as "broken". I disassembled one of those, cleaned the aperture blades and it was working afterwards.

I would not try to repair the EF 17-40L myself, it is a very complex lens. It is very easy to break something or displace lens elements.

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