Resolve Bokeh/Filter issue?

[Nordwil57]

Not sure if this is the best location for this post, but any help is appreciated.

I'm attaching 2 shots from a recent safari in Tanzania that demonstrate an issue I'm having with a new 100-400L. The first (better!) pic is taken by my wife with our "back-up" 300D and 75-300IS lens. Nice and clear, sharp image.
The second was by me with my 350D and the 100-400L.
Other than the image not being as sharp, can anyone tell me what the cause might be for the background to be so wavy/sharp? rather than the typical depth of field softness you see in hers (and my other shots prior to this lens?) I am hoping this shows up in the pics I uploaded...if not, feel free to check out my Flickr page and you will see similar issues with the shots I've posted there...but only with the 100-400! I'm wondering if it could be as simple as an inferior UV filter that screwed up the Bokeh? (Crystal Optics - sold to me by the company selling me the 100-400L). I will try taking some new pics without the filter to see if it helps....

I feel like I'm "salvaging" some of these safari shots, but it really bothers me that I have to worry about this issue.
Sharpening the pic can exacerbate the problem, but the issue was definitely there prior to any post processing as well. Sorry if I used any wrong terminology, still new to some of the terms!

[BrantG]

Should probably ask in the Lens section. HOwever being a 100-400 owner, I can attest to this problem as well. Lots of people say the filter is what causes the bad bokeh on this lens. I'm almost leaning in that direction as well. I plan to remove the filter from mine and shoot without it to compare.

Examples both shot with the 100-400 and both using the same filter:

Bokeh doesn't look "bad"
http://www.brantgajda.com/images/gallery/wildlife/large/elephant1.jpg

Bokeh looks really bad
http://www.brantgajda.com/images/gallery/hdr/large/tiger1.jpg

[Jim M]

I've noticed that from my 70-200 f/2.8 IS as well. Not as bad, but it's there. Reminds me of a mirror lens. I'd say it was camera shake, but it only seems to be in the out of focus background with linear objects, like grass, and it shows up on pictures that are tack sharp in the in-focus areas. Me living in the grasslands, it is a pain.

[Nordwil57]

While I'm sorry others are having similar issues, I sure am glad I'm not the only one!
Jim, I can see where it would be a pain out there, since it certainly seems at it's worst with the grassy backgrounds!
I hate to think I can't trust this lens on another trip, (although another Safari trip is not something I see happening in the near future unfortunately).
I will re post in the lens section as well, and will try to take a few shots without the filter this weekend. If any of you experiment and have ideas, please share them!
Thanks again!

[Jim M]

I plan to give my lens a good test in Kenya in a couple of weeks. Yes, I said Kenya.

[BrantG]

Can't wait to see the results.

[Nordwil57]

Moved the thread to Canon EF and EFS lenses and had some good feedback. Jim, check it out before your trip. General consensus is that it's a filter issue. Crystal Optics had some decent reviews on some repectable sites, and I'm not convinced that a more expensive filter wouldnt have caused some problems as well, maybe not as many. I worry about using no filter at all, the dust gets everywhere, precautions be damned. In hindsight, tho, I would have risked it if it resolved these issues. Dust can be cleaned I imagine, and since we're in vehicles most of the time while shooting, not as much of a risk of poking it with a tree branch or something!
Enjoy your trip!