[davidmanze]

<p style="color:rgb(40,40,40);font-family:helvetica, arial, sans-serif;">dave, with calipers you can't measure down to 0.01 mm reliably. I should take the converter which is neither worn out or malfunctioning to the grinding-lab where they can measure down to 0.1 µm and find out how parallel it really is. Again, even given  perfect manufacturing, an adapter is always only second best. If you enjoy  little read about that:

<p style="color:rgb(40,40,40);font-family:helvetica, arial, sans-serif;">  I read it, Roger is a knowledgeable man no doubt, when he tests multiple lenses for centering /resolution and reports back his percentages of de-centering, you know your unlikely to get the best lens of the bunch, yet you still buy lenses......

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<p style="color:rgb(40,40,40);font-family:helvetica, arial, sans-serif;">     ...same with adapters, buy try keep/return!

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<p style="color:rgb(40,40,40);font-family:helvetica, arial, sans-serif;">    It's lottery out there!........

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<p style="color:rgb(40,40,40);font-family:helvetica, arial, sans-serif;">  The Nikon TC is +/- 0.03mm measured across the faces of the bayonet at 4 X 90°. I've never noticed anything wrong other than I don't like TCs in general. My guess is it's twenty years old.