Originally posted by Imageman You have tested this lens and camera on the map shot you took, its working normally, good plane of focus, no dodgy misaligned or loose elements, the flash is illuminating the scene adequately without any shadows cast by your lens what more can you ask for.
The map shot does
not look like it has even sharpness to me. The Upper Left and Lower Right corners are clearly less sharp than the other two corners. This
may indeed be a contributing factor. Take a few more shots with a map or something similar and look more closely - try to get some text or icons in each corner.
Note that these are the exact same two corners that others and I identified as being curiously in-focus (or in one case out-of-focus) in the action shots. To write this off as a coincidence makes little sense. Also notice that all these shots are wide-open at f/2.8. The effect may not be as noticeable at other apertures.
Originally posted by Imageman Don't expect your lens to pick up and lock on focus in 1 nanosecond. You used a flash, presumably that's because it was low light. Many autofocus systems cannot lock focus in low light. Id be willing to put money on this being at the root of the issue.
How much money would you be willing to put on it? After thinking about it, I remembered just how dramatic the shadow cast by a long, overhanging lens usually is. And it's usually a wider-angle lens that shows such behavior. After realizing how silly my idea was, I tried (unsuccessfully) to back out of it gracefully. But I'm afraid your thought is just as unlikely. The AF system is obviously working quite well on the in-focus portions of the image. And it's not just some random part of the image that's in focus - it's nearly right where he'd want it with a properly functioning lens.