I confirm Sylwek's impression: the main difference between the two systems
was the noise (of lack of it). Difference in AF speed was negligible.
At the end, I believe that a fast AF is faster that a slow AF and a good AF
is better than a bad AF.
USM and in-camera AF motor can both give good or bad performance, if they
are engineered to do that.
If you develop a weak USM module and put it in every lens, you get the same
(poor) result of putting a weak motor inside the camera.
The same probably happens if you have a lot of AF data to process and not
enough computing power at hand.
These are the risks of introducing USM merely for advertising purpose.
I agree that Pentax needs a better AF system, as the *istD doesn't match the
MZ-S in all conditions, not to speak of the best Canons and Nikons. However,
I'm sure their designers know well how to do that. It is not necessary we
teach them.
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)?
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
