Nearly a year ago I got the new model of the Canon 100-400 EF lens.  I had it on back order when it first came out and it arrived just before Christmas so became an impromptu gift to me!  Almost everything about the lens I liked.  However, if you read my initial thoughts on the lens which I covered here, you will have seen I had a concern about softness in one part of the image.  I have used the lens extensively since then and, while I have not always had an issue, I have continued to be concerned about the output in one area – particularly when compared the the excellent sharpness the rest of the image was displaying.

I sent the lens to Canon earlier this year for a service.  I explained my concerns and they took a look and told me it was functioning properly and returned it.  I took it on another shoot and got more shots which did not look right.  This time I emailed CPS and provided them with some sample shots.  They suggested it didn’t look right and told me to send the lens back in with a description of everything to date along with more sample images on a card.

I now have the lens on its way back to me.  Here is what they found.

Your product has been examined and it was found that the optical assembly was broken causing the auto focus to operate improperly from time to time. The 6th group lens and 2nd group lens were replaced. Product functions were confirmed.

It is nice to know that I wasn’t imagining things but a little disappointing it took this long to get to the bottom of things.  Of course, I could have done some of this sooner if I had been more certain of the problem.  In future, I will be a bit more willing to trust my instincts.  Now to get the repaired lens in my hands and test it!