Originally posted by angus Will try to find out more on Friday, but I guess they won't let the cat out of the bag as they haven't done so already. Just hope that they'll feature the DC-drive rather than the revised SDM. I'm not so bothered about in lens OS, quite happy with the in-body solution with my 250-600 and I've yet to see a test which really proves one or the other to be better. A portable long zoom with high quality would be really nice...
Just for clarity - SDM isn't literally one motor that Pentax uses in all SDM lenses. SDM just refers to ultrasonic driven motors, similar to Canon USM, Nikon SWM, and Sigma HSM. DC is a different of motor (I believe a step motor?).
SDM isn't inherently bad, since other manufacturers have working ultrasonic motors that don't fail like the one in the 16-50. In addition, the Pentax 18-270 uses a SDM motor, but the Tamron equivalent is Tamron's hypersonic motor. This leads me to believe that Pentax, instead of changing the AF motor in the 18-270, merely rebadged the motor to SDM as it is the same type of motor.
Thus, I wouldn't necessarily stigmatize SDM in a newly designed lens. As long as it literally isn't the same motor from the 16-50 and 50-135.