EF 70-300mm f/4.5-5.6 DO IS USM not focusing correctly or softly.

[Reximus]

I recently purchased a used EF 70-300mm f/4.5-5.6 DO IS USM from bhphotovideo.com, I purchased it used and on their rating system, it was rated an 8+, meaning that there were some signs of wear but otherwise the lens was flawless. After receiving the lens, it was just as described and works wonderfully, I'm enjoying the lens very much. 

I've started to notice an issue with it however, the lens seems to produce soft images when all of the AF points are on the subject no matter what focal length or aperture setting I have it on. I've been reading through the forums and I've seen other people having an issue similar with various other lenses and I've seen solutions ranging from cleaning the contacts, to microadjustments, to sending it in for servicing. 

Does anybody have any advice to what would be the best route to go with on this issue?

If it helps, I am using this lens with a Canon EOS 70D. The 18-135mm lens that came with this body works wonderfully, and the EF 70-200mm L I had rented a few weeks ago worked wonderfully as well.

Thanks in advance for any advice.

Rex

[ebiggs1]

Right off the EF 70-300mm f/4.5-5.6 DO IS USM is never going to best or equal a 70-200mm L lens. No matter which version you tried.

I would select and use just the center focus point on the camera. Shut all the others off. Are you sure the issue is not camera movement and not the lens? You might want to invest in a tripod. When you zoom to 300mm with your combo, you are experiencing what a 480mm lens would see. Holding that motionless, at f5.6 can be a tall order.

Try setting it up rock steady and do some shots.