ok then you might need to do a bit of research (dont have the links
with me)
Maybe so. I am going by what I have read and my experience using
friend's 20D and D200 with USM/AFS. Seemed to focus and track much
better than my screw-drive lenses.
re To get a taste of the 2nd and 3rd quesitons, here is a comment
from Klaus from photozone:
"An ultrasonic motor doesn't necessarily translate to faster AF -
this is design-dependent. In fact the Minolta APO HS lenses were
supposed to focus pretty fast despite being screw-mount variants
(driven by the camera). Several non-SWM Nikkors also focus very
fast on the D200.
Does he have numbers or just general impressions? How new are
these USM lenses? My Nikonian friend said that some of their screw
drive lenses are pretty good but none compare with the AFS lenses.
It is a slightly different topic in EOS (and 4/3) land where you
only have in-lens AF motors - either ultrasonic or via a
conventional micro-motor of some kind. "
If you look up the popphoto AF tests you will also see that the
KM/a100 AF is almost always faster than the others - (note this is
fully lens dependent.)
Are you sure of this. I get PopPhoto and they recently said of the
A100 compared to the 400D: "A100 focuses faster at lower light
levels" and "the Rebel...has more sensitive AF". So that doesn't
seem to indicate the A100 is all-around faster. I'll go back and
compare the reviews though. But I think the problem with the
PopPhoto tests is that they don't have a common lens that they test
them with AFAIR.
I do believe that there is significant differences (esp tracking)
in the big long teles but your catergorical statement raises doubts
about what you tout everyday on this forum as 'facts'.
Facts in what regard. Most people have reported that USM/AFS lense
are faster than screw-drive. Why would they track better if they
weren't focusing faster? They are also much quieter. Have you
ever tried USM or AFS? They seem much more "professional".
One last thing: Why would Canon and Nikon be going completely
USM/AFS if it wasn't better? Why would Sigma develop HSM? Why
would Pentax? Why would Sony?
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fjbyrne