Sweet spot ?

Hi folks, this has gone from a sweet spot question to a focusing issue.
even with a lens correction of +10 its still well out.
any ideas ?
No 1 is no correction
no 2 is focused on the 3rd screw on the right
no 3 is plus 10 correction
no 4 is manual focus.
p/f is not an issue here, just dont know what can be done about focus.

I should point out that the point of focus is the 5th screw from the right, which is slightly thicker than the rest.

Are the shots cropped?

Shot two looks like it's focused on the 5th screw, or at least between the 4th and the 5th. I would over-ride the AF in this sort of situation normally, as the focus points do lock on the wrong thing sometimes. Is the lens front or back focussing in normal shots, when there's no chance of the AF system being 'confused'?

The only thing I did was crop to post on here. The 2nd photo I focused on the 3rd screw on the right in order to get the focus where I wanted it.
It seems to be back focusing more than the lens fine tune can adjust for.

Personally, I would try to simulate some real world shots e.g. portraits and see if the lens performs OK there. I can't tell how big these screws were in the frame in the original shots. It could be that the central focus point is just too big to differentiate which screw the focus should be on. Or it could indeed be back-focusing.

As this now seems to be a focusing issue, this thread is probably in the wrong forum, if any mods or admins want to rename it or move it
Cheers
Derek

Moved to Troubleshooter.

Thanks john.