Help with the Canon 100-400mm EF f4.5-5.6L IS USM Lens

Hi Thanks for that, have tried manually focusing still blurred lens now safely in repair shop. Thanks for everyone's input has been a great help.

I've shot thousands upon thousands of pics through my 100x400. What I've learned over time is that Canon has had some quality control issues with this lens and some come out great and tack sharp and some come out not so great, like yours and mine. I got mine fixed and it is now tack sharp at 400mm. When you get it back do the following. In the menu find the "AF Point Display" option and enable it. This will cause the focal point(s) that the camera selected to be displayed on the pictures when you review them in the camera. Set the AF mode to "Manual Select-Single Point AF" if your 550 supports that mode otherwise set it to "Manual Select-Spot". Set the camera to the AE mode and f5.6. Now shoot a picture at both 100 and 400mm using the "spot" focus. Now review the pics and see if the focus highlight is the same as where you focused. Canon will set the focus to "specs" but there are always tolerances to specs (+/-). At 100mm it will be right on but at 400mm the focus spot might be slightly off from where you thought you focused. Spec tolerances get amplified at greater distances. Set a ruler or yadrstick(meter stick?) facing you at a 30-40 degree angle next to the object you are taking a picture of and at 400mm take a couple of pictures. Now take that picture to your computer and enlarge it. Is the in focus area the same in front of and behind the object? probably not at 400mm. The 7d, and others will allow you to adjust the behind/in-front focus on a per lens basis. An inexpensive product by LensAlign.com will allow you to centrally adjust your focus. If you are not happy when you get the lens back, send it back until they get it right. It is a great lens and you can take some outstanding pictures with it. I do a lot of BIF (birds in flight) photography with mine.

Sorry for the delay the lens has been with canon and has been recalibrated, however on return no improvement. Have now tried a friends 100-400mm lens which worked fine with my camera, we then used my lens on his camera which worked fine. Then tried my lens with my camera and again it continued to hunt struggling to focus.

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Originally Posted by Clive

Sorry for the delay the lens has been with canon and has been recalibrated, however on return no improvement. Have now tried a friends 100-400mm lens which worked fine with my camera, we then used my lens on his camera which worked fine. Then tried my lens with my camera and again it continued to hunt struggling to focus.

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What a nightmare for you. I guess the only other option would be to send in both the camera and lens to Canon?

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Originally Posted by Zarkam

I've shot thousands upon thousands of pics through my 100x400. What I've learned over time is that Canon has had some quality control issues with this lens and some come out great and tack sharp and some come out not so great, like yours and mine. I got mine fixed and it is now tack sharp at 400mm.

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Although I have not had QC problems with the several lenses I have purchased new: 70-200mm f/4L IS, 17-55mm f/2.8 IS and 28-135mm f/3.5-5.6 IS; I have had problems with the two new anon DSLR cameras I purchased (10D and 350D). The three that I purchased as Factory Reurbished items had no problems (30D, 40D and 7D) The problem I thought I had with my refurb 7D was actually caused by operator error.

As a result of my purchasing experience, I would be inclined to get a refurbished Canon item over a new one. The refurbished items all have been inspected before shipping. This, apparently, is not the case at the assembly line where they only test items occasionally.

If most other gear we bought has the sloppy QC of Canon, there would be a cry out against them. Imagine, as many autos of any one type failing as the percentage of Canon gear that fails:eek:

Thanks for your help, I have finally got the lens back it turns out it was the filter that was faulty. Never thought of that!!!! But I am happy with the results now.:)

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Originally Posted by Colin Southern

Any filters on the lens? Rear element clean?

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Originally Posted by Clive

lens does have a CPL filter

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Originally Posted by Colin Southern

It's VITAL that you remove this for testing.

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Originally Posted by Clive

Thanks for your help, I have finally got the lens back it turns out it was the filter that was faulty. Never thought of that!!!! But I am happy with the results now.:)

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Got there in the end :)

If you are going to get a new polarizer filterr, double check that it is indeed a CPL (Circular Polarizer Filter) and not a linear one. A Linear Polarizer Filter is likely to confuse the autofocus on the DSLR.

http://en.wikipedia.org/wiki/Polarizer

b<e
Robert