Originally posted by axl not with sonic type motor AFAIK.
all their lenses codevelped with Pentax use conventional motor in lens...
too bad
Originally posted by Class A Some HSM lenses use different (better) ring motors.
Some use micro motors similar to SDM.
None have a shoddy history like SDM.
Only the DA*16-50, DA*50-135 and 17-70 have big problems with the AF, i'm still not sure what's going on there. if they use different SMD or if it's AF mechanism.
From what i read the 17-50 use a geared HSM not a ring-type not sure about other lenses.
Originally posted by Clavius But why not just use bigger, more powerfull DC motors for the lenses with the bigger elements then?
More powerful motor means more power which comes with their own limitations with the electronics and the battery, they could use DC with different gearing but means lower speed.
Besides why would you want DC when SDM seems to be working really well with the more recent DA* lenses. DA*60-250, DA*55, DA*200, DA*300 all are so good as problem free.
Pentax should never have used the KAF2 mount, i think that's where most of the problems lies with the dual (triple if we count manual) focusing mechanism