Do I have a Problem with my EF 100-400mm

I quit using UV filters a couple years ago. Why put a cheap piece of glass on the end of your nice 'L' lens? Think of all the technology you are paying for in that fine piece of 'L' glass, and then you are basically defeating it by shooting through a cheap piece of window glass (slight exaggeration). If you are worried about protecting your lens, use the hood.

jmo

-Jim

Keith R wrote in post #2174250
Not with an IS lens it ain't, George...

Looks like a filter thing to me too.

I didn't know it was an IS lens, but even so, how do you knowit was switched on.

If you think it's the filter have a look at his other photos and explain how come they're sharp?

As I mentioned earlier, I had exactly the same issues with my 100-400 and it was the filter. (Cheapish Hoya) It also caused this problem intermittently. It must be related to the light direction or something that does not affect every shot.

curiousgeorge wrote in post #2176479
I didn't know it was an IS lens, but even so, how do you knowit was switched on.

If you think it's the filter have a look at his other photos and explain how come they're sharp?

The position of the light source in relation to the lens plays a big role. It has all the earmarks of being a filter issue. We don't know for certain that the IS was on....but I suspect that he would have no reason for turning it off.

I can tell you a funny story, about Filters .... its saved my brand new 70-200 2.8 IS
The week that it arrived my wife and I decided to go to whipsande zoo... I was really looking forward to testing out the lens - My wife and I were walking side by side she.. swinging her sony digital compact it just so happening that it made accidental contact with the front element on the lens luckily i had a UV filter it did however suffer a slight scratch.... thank goodness I put the UV filter on that day....

yes I had IS on , here are some more examples, but to be honest guys I think its looking like a focus problem..
these are all taken at 400mm @ F5.6 yes I know it should be around f8

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Yes this does look like a focus problem, perhaps the AF locked on just in front of the bird, can happen if the subject is small in the frame like this.