Hi--
>You are correct. Since the image of the tap is much smaller on the
>28mm lens, an equal amount of blurring will wipe it out much worse
>that for the 200mm lens. Assuming both lenses are f/4 for the moment,
>the blur should be 2mm/4 = .5mm in diameter in both cases.
>
>And I'm correct too. We are just using different metrics.
>
>We theoreticians are a feisty lot! :-)
>
>BTW, I think there are some lenses that are partially internally
>focusing. The total effective shift may be more that the end of the
>barrel moves out. (Apparently that was not the case here.)

--David Jacobson

Yes, which is why I chose those two lenses - no floating elements,
no zoom focus - just straight barrel extension with lenses close
to the same speed (though one COULD depress the DOF button, but
SUCH effort...!). David