Now that this lens is older no one has posted for a while. I had the lens but sold it in September 2017 because I found I liked my 70-200 f2.8 better and it was difficult to carry both. However there are times (especially with birds) that my 70-200 is not long enough, even with the 1.4 extender. So I just purchased the 100-400 ii again using the current $400 instant rebate. Here is a test shot from my first outing with it this morning. This is with the 1.4x iii extender. Image is cropped a little but otherwise unadjusted JPEG from 5D4.