Canon 100-400mm f/4.5-5.6 USM IS II

Started Jul 2, 2019 | Discussions thread
John Sheehy Forum Pro • Posts: 23,694
Re: Canon 100-400mm f/4.5-5.6 USM IS II

ohthatgirl wrote:

I have had my lens now for roughly two years. At the beginning, the images I took using the lens were sharp, but over time I noticed they were losing their sharpness. I am using it along with my then new 7D Mark II. I fooled around with micro adjust calibration, AF settings and even considered sending it in to Canon to have a look. I also noticed almost from the start a small dust particle on the inside of my lens - which mainly irritated me but did not impact the image. Just recently I went on a road trip and cleaned my lens and Hoya filter before I left. I have always had my filter on my lens from the beginning. I used a magnifying glass and light to clean it and noticed the same dust particle and several more. On my recent road trip my images looked fine (and continue to look fine) however, on a very bright sunny day the light was shining on my lens so that I could see a fine vertical crack had appeared. I have no idea how long my lens has been like this because in normal light, you cannot see it at all. It's there and not impacting my images, but has anyone ever heard of this? It has not been dropped or even low impact in anyway.

Any optical sharpness vs autofocus question is very easy to solve; just go outside, find a wall in bright sun, shoot it at about an 80 degree angle with a fast shutter speed, and look at the part of the wall most in focus and see how sharp it is.  Try with IS turned off and turned on.

If you can't find the sharpness that you used to have, then maybe something did happen to the lens.  If the wall is sharp somewhere in the frame, then AF calibration is your issue.

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