Is this lens decentered (EF 100-400mm f/4.5-5.6 L IS ii USM)?

[ryanengphoto]

Hey yall, I picked up a used copy of a 100-400 ii a couple months back to 'upgrade' from my 400mm F5.6L prime. That lens was razor sharp and I loved it, but I wanted the zoom and the equal if not better sharpness from what I read online. At first I thought it was fine and that I was maybe just missing AF, but I had a hunch something was not right. On Saturday I photographed a bird swimming on a lake (clear background, bright direct light) and I noticed the pictures really were not sharp on zooming in. This is where I finally felt sure it was not just a skill issue. I tried going through AFMA on my 7d ii to figure out if it was back/front focusing, and while it did sometimes, that was not the whole issue. It seems on direct comparison to the prime, it is softer.

I will attach a direct comparison photo, it is of a calendar taken pretty much front on with 1/40s, F5.6, and ISO 1600. It is clear especially in areas like the bottom left that there is a lot of softness that almost resembles diffraction artifacts going on in the zoom. It is not motion blur, IS is off so it is not IS, the pictures were taken with a 10 second timer on a tripod so they are totally still. They were manually focused the exact same way, it is not AF. I have tried with and without lens hood, it is not caused by light on the front element.

The pictures are linked in this reddit post since I don't have them on this laptop and I can't upload .webp: https://www.reddit.com/r/canon/comments/1r6j2sf/comment/o5r9eei/

[ebiggs1]

"...I will be sending it off ..."

Probably best course even if for nothing more than peace of mind. Canon will check it out.

[ryanengphoto · Accepted solution]

For anyone in the future with a similar issue: I was quoted $569 for the repair.

[ebiggs1]

What were they going to do for $569 bucks?

[ryanengphoto]

This is their official answer: 

Repair Complete Comment:

"Your product has been examined and it was found that the lens was out of position causing poor image quality. Adjustments were carried out to sharpen resolution and dust was cleaned from inside the lens assembly rear element. Product functions were confirmed. Thank you for choosing Canon!"

So sounds like it was decentered in one of the many elements to me. Not too clear lol, they quoted based on 'a tiered rate repair', i assume because they would have to open it up to figure out what exactly was wrong before doing the repair and it was to cover themselves in case it was worse? Not exactly sure, but it's on its way back, fingers crossed it's sharp now 🙂

[ebiggs1]

Good luck, I'm pulling for ya.