Originally posted by Rondec Pentax isn't making any new lenses without in lens motors. This includes the coming DFA 21 limited.
That said, it isn't as though SDM motors were anything to write home about. I'd like to see you track something at 10 fps with a DA *55 or DA *50-135.
Good Lord, try tracking a snail on a cool morning at 1 fps with the 60-250. The snail will still outpace the lens. This is what happens when you replace a button battery with a motor. The old SDM was bad technology, plain and simple. It was failure prone and it was slow. I could manual focus faster and more accurately with my 60-250, which was a good thing considering how unreliable the motor was about working in the first place.
The new motors seem much stronger, and one hopes that they will prove to be more reliable. I don't compare to other brands, so I don't know how AF speed compares to other brands in the same price range, but I can now track a snail in the garden, so it's definitely improved.
---------- Post added Jul 23rd, 2020 at 12:06 PM ----------
Originally posted by stevebrot ...which has little to do with whether the focus motor is in the body or the lens and a lot to do with the AF detector and whether or not the body has a dedicated AF processor.
Steve
A few years ago, like 15 or more, there was a discussion about this on the PDML. There were a couple of points brought up. One was that one could only accelerate a screw drive so fast before the lens itself was damaged by the gear train stripping it's teeth. The other was the inevitable lash in the mechanics causing a certain level of inaccuracy, lash that only get's worse as the lens is racked back and forth at the high initial torque required to get it moving.
I have often wondered if the DA Limited's weren't so slow to hide this within depth of field.