The other day I was doing some testing with my 14-35mm f2 and EC-14 tele-extender (a combination that I hadn't used before) and noticed that the images at wide and tele were pretty soft. There was certainly nothing wrong with the EC-14 as far as I knew, so I decided to see if AF focus adjustment would improve things. To cut a long story short, I went through numerous adjustments and finally settled on a -4 adjustment for both ends of the zoom. This is actually quite a substantial adjustment and when I went through the process with my E-5, I think the max was +/-2 for one of the lenses. So clearly the m4/3 bodies have some differences. However, it's great that you can do these adjustments and get things spot on. As for the 4/3 lenses themselves, I haven't had to adjust any of them, as they appear to focus accurately. However, you do have to set the AF to 'Default Data', even without adjustments, so that the camera can use the factory settings for 4/3 lenses. I might have to do some focus testing using the EC-14 with my other lenses as well.