Quote Originally Posted by cliveh View Post
Can someone help me out here?
Some lenses do suffer from focus shift, but most don't.

So Michael described a method of checking whether your lens is one of the problem ones.

Perform the suggested test. If you observe focus shift, you will need to build a "focus at working aperture" step into your workflow.

If the test doesn't reveal any shift, you can confidently focus at maximum aperture for all your work.