I think my 300mm F4L IS is broken....

Just got back from taking pics of Blue Angels air show in Seattle, I've been shooting when I noticed that my IS is not on so I switch the IS on than started shooting when suddenly I noticed something wrong.....it is having a hardtime focusing....so I switch the IS back off that when I noticed that something inside my lens won't stop making a click sound, when I look at the viewfinder I noticed the mirror keep jumping up and down and I won't focus.....I can not take any shot....but if I switch back on the IS everything seems to be normal....I'm out of warranty but would like to have this fix....what do you guys think is the problem with it? and how much I am looking for in terms or repair cost? I would like to know before calling the canon so I would know how much to expect....thank you very much.
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if it's working with IS on, you could use it with IS on, i'd keep playing with it. this problem might go away on it's own. was your battery good?

rick_reno wrote in post #14814753
if it's working with IS on, you could use it with IS on, i'd keep playing with it. this problem might go away on it's own. was your battery good?

Hi Rick thank you for your reply. It actually occurred right after I change my battery. The new battery that I just put in was fully charge. It is a third party but I've been using that battery and never have a problem like this. I notice also that in my 300mm in the barrel right after the glass where you connect the camera something circular is loose is that normal? Never notice it before. Thanks.

Peter2516 wrote in post #14814861
Hi Rick thank you for your reply. It actually occurred right after I change my battery. The new battery that I just put in was fully charge. It is a third party but I've been using that battery and never have a problem like this. I notice also that in my 300mm in the barrel right after the glass where you connect the camera something circular is loose is that normal? Never notice it before. Thanks.

Can you explain this better? Reference a photo (either yours or another EF lens). It doesn't sound normal to me, but I'm not sure why it'd make the IS do crazy things. It actually sounds more like the IS unit cannot hold itself in a stationary position and may need replacing, but you should certainly look into this "loose" part first.

As a precaution and to eliminate one more suspect, you might try cleaning the contacts.
Sure wouldn't hurt, anyway.

canon won't give you a price on repair over the phone...you'll have to send it in first....

Keh did a repair to my non working 400 2.8 and WOW!! Great quality. I believe they have general quotes on the site just for reference. Www.keh.com

Someone has the same problem and they were qouted 385.00 something total and because they are cps member ended up paying 159.00

Skul wrote in post #14816445
As a precaution and to eliminate one more suspect, you might try cleaning the contacts.
Sure wouldn't hurt, anyway.

I did this already and still did not work...

jmcgee131 wrote in post #14817280
Keh did a repair to my non working 400 2.8 and WOW!! Great quality. I believe they have general quotes on the site just for reference. Www.keh.com

I am going to give them a call thanks for the info..

phreeky wrote in post #14816323
Can you explain this better? Reference a photo (either yours or another EF lens). It doesn't sound normal to me, but I'm not sure why it'd make the IS do crazy things. It actually sounds more like the IS unit cannot hold itself in a stationary position and may need replacing, but you should certainly look into this "loose" part first.

It is very visible and when I shake it looking down at the other end of the lens (where you connect the lens to the camera) just right after the glass if you shake the lens you can see there is something loose that is moving.....it is a circular object.

I brought it in to a local camera repair shop and the technician sad that it is the IS not working properly, he is saying about a magnetic field that suspends the IS when it is on....