Originally posted by Entropy There is no fundamental design flaw with SDM.
I didn't write anything to the contrary but as you are addressing the point, here are my comments:
- There seem to be way too many reports about SDM failures to make these unfortunate, but particular incidents.
- There are users who get their SDM lens back from repair only to have it fail again shortly after.
- There are users who went through a high number of failures. Peter Zack had three 16-50 zooms which all died.
- One hears a lot less about SDM prime failures. Maybe the small SDM motors are a bit too weak for zoom lenses.
All that makes me think that there is probably a fundamental issue.
Note that the Pentax SDM solution is dubbed "micro-motor" in Canon speak and Canon uses it for their budget line only. Their proper lenses receive the robust ring motor technology. I guess a ring motor makes a lens slightly bulkier and Pentax wants to keep their equipment as small as possible.
Originally posted by Entropy Calling SDM fundamentally flawed because initially released motors were prone to jamming is like calling the K-5 fundamentally flawed because one manufacturing batch had residue left on the sensor.
You are right, but unfortunately, the
SDM failure stories don't seem to stop so it seems unlikely that the problem was caused by an initial batch of faulty motors.