Originally posted by MJKoski My 100mm WR is manufactured in 2018 and I have used it 3 times during the last 3 weeks it does the usual "zikk-zakk-zup" screw sound as 43mm ltd and 35mm ltd I used before that. It would require worm gear drive to make it accurate and not go into back-front-focus hunting loop.
The back and forth adjustments have nothing to do with play in the screw drive mechanism, especially on such a new lens. This is the AF algorithm making very fine adjustments based on feedback from PDAF or CDAF data. Actually, you can see the exact same thing happening on a number of electronically-driven lenses (I can show you it happening on my Sigma 17-50 f2.8, for instance). It's just not as audible.
Originally posted by MJKoski Not modern design and should be removed instantly. AND, it totally wrecks smooth focusing feel when using a macro instrument in manual focus mode (preferred way).
I agree that screw drive isn't a modern design, and we can see that Pentax has been moving away from this with its more recent lenses. So that's good news, right? Of course, there's still a back-catalogue of the older screw drive models for those that want them. No sense in getting rid of those when they're so good optically, and until there are replacements (which will take some considerable time).
Again, though, it's the way you choose to express critique that takes away from what otherwise might be helpful opinions, and aggravates other members. To say that screw drive "
totally wrecks smooth focusing feel" is such an exaggeration. Can we feel that there's a geared mechanism in play? Sure, a little. Does it "
wreck" the feel? Of course not... at least, not on
my copies of the 35mm Limited and DFA100/2.8 Macro.
If you want a nice, oil-damped manual focusing mechanism, buy a manual focus lens. Even my electronically-driven lenses don't feel as nice as a well-damped manual focus model.
As always, we choose our instruments based on our requirements.