Another proof that a well engineered AF system can work better than a bad
one (regardless of the technology involved): the Contax 645 (USM) vs. the
Pentax 645N (in-camera AF motor).
I've used the Pentax 645N and I was impressed by its speed and
effectiveness.
Those who compared above cameras (not me) said the Pentax blows out the
Contax.
Of course, I won't deny that a good USM can blow out a bad in-camera AF.
Dario
----- Original Message -----
From: "Sylwester Pietrzyk" <[EMAIL PROTECTED]>
To: <[email protected]>
Sent: Thursday, January 12, 2006 9:28 AM
Subject: Re: new AF system soon (when D2 arrives)?
Adam Maas wrote on 12.01.06 2:38:
Pal, have you shot with a USM or AF-S lens? There's no comparison in AF
performance. USM absolutely blows screw-drive AF out of the water unless
you have either an ultra-light lens (like a 50mm) or one of the very few
cameras with a truly massive AF motor like the F5. I simply could not
believe the difference in AF performance between my old *istD and Tamron
28-75 f2.8 and the EOS 3 with a 28-105 f3.5-4.5 USM lens. The EOS was so
much faster I initially didn't believe my own eyes (Although some of
that likely has to do with having the same AF unit as the EOS-1D). USM
is needed in the Pentax line, badly.
You were comparing AF performance of heavy optics of metal built non-IF
f2.8
lens to light, plastic, IF-equipped f3.5-4-5 lens... In 2004 when we meet
with Dario we compared AF speed of two identical lenses in good light -
Sigma EX 70-200/2,8 - one mounted on Dario's *istD, naturally screwdriven
AF, second one with HSM motor and mounted to Nikon D70. I can assure you
that there was no significant difference in AF speed at all, I've got even
feeling that *istD was somewhat faster, but I could be under some
influence
of AF motor sound in *istD :-) I hope Dario will read this and confirm my
observations. The conclusion is, that if you have two mechanically
identical
lenses, than there will be little difference between USM and good classic
drive. Two main advantages of USM are its quietness and possibility to
manual tweak of focus (FTM - this is now available in new Pentax lenses as
QSF too).
--
Balance is the ultimate good...
Best Regards
Sylwek
