occasional disagreement between film and VF focus
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
(more obvious with short lenses
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>It should be the case that the *visual* obviousness depends only on
>the f-stop. There are two reasons it might seem more obvious on short
>lenses, though. 1. They are move often the ones with large
>apertures. (Unless you are talking really short.) 2. The focusing
>difference per degree of focus ring rotation is much smaller on a
>short lens. So if you are comparing AF with MF, a small misadjustment
>takes a lot more focusing ring rotation to correct.

Wha' yuh caught me with this one again?! Isn't this where I came in?!
BUT, Ahz reddy dis tym! I put a 200mm f4 on the camera, focused it on
the end of the tap in the darkroom, then focused the lens forward for
2mm more barrel extension. I then took a 28mm f3.5 and did the same
thing. Technically, you are right: the point reflection on the tap was
rendered as the same size disk for both. Otherwise you are wrong: the
image of the tap was soft, but recognizeable with the 200mm; the image
of the tap with the 28mm was a wipe-out, not recognizeable. Also, if
either the lens mount to film distance, or viewing screen error, was
2mm in error on the plus side, the 200mm would still have much of its
focusing range still available (2mm is small compared with the full
focus extension range of the 200mm), and would visually miss infinity
by only a bit. The 28mm would be stuck near minimum focus in its range,
and the visual image of infinity subjects would be very poor. So I
stick by my original statement. We pragmatists are a feisty lot!
David