Originally posted by victormeldrew I'm not sure about this, as it is would be impossible to tell the difference between front and back focusing, let alone amount.
But indeed the focus target must be flat. The focus point is not a pinpoint, but an area, so with a curved object it will be impossible to control where the focus will lock on.
Look up GhettoCal. It's a free printable focus calibrator that you can build yourself quite easily. Alternatively placing a ruler on a table and a flat vertical high contrast target in the middle would be better than nothing (or a pole).
Thanks for the tip on GhettoCal, seems like this lens is going back to the seller if i cant help it.
Left: Live view single point AF Zoomed 100% 1:1, Chart in focus, however, ruler is pointing that focus was around 0.5.
Right: +10 adjustment, live view auto focus. Auto focus is still off, ruler is pointing that focus was around 1. As a result, even with +10, the lens is still back focused, which is in line with all my previous test.
I have also did the same with -5 just to test, and +6 +8 and finally +10.
At +10, it was the closest to the live view auto focus. however, +10 is definitely not enough for this camera/lens combination.