soft focus on Canon EF 100-400 f4.5-5.6L lens w/EOS 7D

[charlesleblow]

My daughter is currently disabled and I bought this lens for her last year about this same time. She isn't a novice to Bird photography. The lens was used through a dealer as that was all I could afford. It worked great for the past year (sharp focus at all focal lengths) but now my daughter says (and showed me some photos taken with the setup) that auto focus produces an image that is much softer than it was when she first received it and I have viewed her images) She has used the tripod to eliminate shake, with and without a gimbal, self timer etc, She is shooting fast enough, ISO doesn't make a difference nor does it change wide open or stopped down...the problem persists. She is an avid Birder. Also is the lens still repairable through Canon USA. I am long time member and I know that I will have to bear the cost of repair. But it's not listed on the repair site.

I am writing because I have about 20 years experience with Canon from an early EOS 650 to current set up 5DMKII, 6D, and a host of L series lenses from wide angle to 70-200L with 2x extender shooting mostly landscapes. I am permanently disabled with Parkinson's so I'm not as sharp or good at dealing with complex issues as I used to be.

Thanks for any help-Chas

[ebiggs1]

"One shot is where we will start for sure!"

Absolutely, I have seen it numerous times before. Folks switch to Ai-servo and now get soft or OOF images and immediately think there is something wrong with the camera or lens. It is a mistake and disservice when someone tells new photographers to jump past the basics when they are still learning how to use their camera.

KISS is best at the beginning.