Hello Julian,
> I find that the edge of a wall or window or door gives vertical-only
> detail.
These didn't work for me, at least not by lamp-light. Also, I tried focusing on
the edge of a large blank white card on a dark brown table, with inconclusive
results (sometimes no sensor would focus, sometimes more than one would).
> You can confirm that there is no horizontal detail by trying to focus
> on your target using a horizontal-only sensor.
Sometimes it did focus and sometimes it didn't. Hence my conclusion that my
results weren't conclusive. :-)
> I eagerly await the outcome of your experiment to answer the question:
> Does the EOS 3 have any vertical AF sensors at f/5.6?
Ah! In that case I will need to try using the 2x extender on a 200/2.8L, since
that's the only way I can get any of my lenses down to a maximum aperture of
f/5.6. A test best left until daylight. . . .
Craig
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