Originally posted by Anvh Your comparison is silly and you know that.
Not silly at all, AFAIC.
The way you are arguing, it appears you should be switching to Canikon because they have lens-based image stabilization. They can "fine-tune" the stabilisation to the lens, have optimal motors, etc.
If you see the advantages of a body-based stabilisation approach, however, you should also see the advantages of a body-based AF approach.
Originally posted by Anvh The SDM motor and the DC motor are placed near the mount so if you remove the cover there you've acces to the motor, that are 4 screws i believe.
And then you marvel at your broken SDM mechanism? Sometimes the DIY method described in this forum may help, but other times the SDM motor just needs replacing (ask those who had this item on their service bills).
Originally posted by Anvh The motor in the lens has one clear advantage, you can finetune the motor specifically to the lens.
Or you just fine-tune the screw-drive gears specifically to the lens. Where is the difference? One can even imagine that the camera operates the in-body motor differently based on the lens recognised. I don't think that's ever necessary, but it would be a possibility.
Originally posted by Anvh About your last sentence as far as i know Pentax isnt doing that because if the SDM fails it often fails for a reason so if you switch to screw-drive you dont know what will happen. If after 2 months the whole AF system in the lens is jammed and also break the in camera motor...
How did you learn about this alleged motivation?
To the best of my knowledge, no one has ever posted any inside knowledge as to why the many pleas to allow engaging screw-drive AF as an alternative to SDM (in the case of SDM failures, but also when you want to use certain teleconverters) has fallen on deaf ears.
The main hypothesis is that Pentax appears to be avoiding to implicitly acknowledge the abnormal frequency of SDM zoom failures.
Have you read the threads about SDM failures? I'm not aware of any case were the reason was any other than a jammed SDM motor. The screw-drive mechanism is decoupled from the SDM train, so it will drive the lens even if the SDM part is jammed.
If anything else were wrong, the camera AF motor would most likely deal with it, unless you forced the matter.
Originally posted by Anvh Anyway they already have said not to make SDM/DC lenses with screw-drive anymore so that makes the option somewhat obsolete.
The many users who had their dual AF mode SDM lenses serviced (sometimes more than once) because of a jammed SDM motor and who would have happily avoided the service bill by engaging the screw-drive alternative disagree with you.
I believe it would help used market values for SDM zooms, if people had the chance to engage screw-drive AF, rather than being forced to pay a substantial bill in order to gain AF back.