[Anvh]

My guess is that the DC motor is something designed and used by Tokina, and Pentax is not involved in "choosing" to use it. See this thread here.

So the Pentax answer of "DC for budget lenses" means that Tokina is moving away from screwdrive in all of its mass-market (later rebranded for Sony, Pentax, Nikon, etc.) lenses - probably because a major rebranding customer (Nikon) no longer puts screwdrive motors into its low-end bodies. It's possible that when the (re-hired?) lens designers at Pentax design a new lens, they have a choice to use SDM and/or screwdrive, and only if they contract Tokina to build it would they get the option of DC. Tokina would then get the optical design for their own sales, which might not be worth it for Pentax.

• But why does Pentax stick with SDM, and not come out with SDM2? No idea, but until new Ricoh-era lenses actually come out, we won't know if they have stuck with it!
• Why not license the DC motor from Tokina? Again, who knows what the agreements would involve, or if it's worth it (maybe it only works on light zooms).
• Why is Sigma's HSM so much better than SDM? Sigma (apparently) doesn't license designs or tech from, or to, anybody else, so they either get it right or lose sales to Nikon SWM and Canon USM-equipped OEM lenses. Do they care about Pentax SDM? Sigma can barely justify mass-producing the K-mounts, it sometimes seems.

Nikon already use them for a long time in their budget lenses no idea about Canon, it's just a DC electro motor so nothing special about it really.

About your list
* SDM is SDM, an ultrasonic motor, why won't volkswagen come with a diesel version 2 motor? anyway Pentax have said not to make any KAF2 lenses anymore so hopefully the simpler design of KAF3 would improve reliability.
* DC motor is just a DC motor no license needed.
* sigma use ring type for most, same as canon for their high end lenses maybe that's it and they never were tempted to do dual AF system but look at the list of lens rental no brand is AF problem free as you can see.

[lightbulb]

SDM lenses are definitely better than DC lenses. It says so right in the price list.

You must have a closet full of Canon L lenses!

[Anvh]

Thanks for the explanation. I am actually eyeing on 5D III and waiting for reliable reviews to pull the trigger. If there isn't much reason to stay with Pentax I would go into Canon system. I find Pentax a bit lack in tackling their problem and communicating with its supporters, not good. But I respect their culture and wish them well.

You think the grass is greener?

[lightbulb]

Not sure about greener, but the green is definitely faster and putt more accurately haha! Anyway life is short, I am going to do things that make myself and those around me happy!

[Anvh]

I just never liked the handling of Canon, they don't fit me.
Nikon is a better fit for me but I'm thinking to save my money and just buy a digital 645 camera for studio work instead of taking the step of FF.

[panoguy]

* SDM is SDM, an ultrasonic motor, why won't volkswagen come with a diesel version 2 motor?

Volkswagen (and everyone else) has been improving diesels for a century. As you say, Sigma uses "ring type for most, same as canon for their high end lenses" but these are still ultrasonic motors, right? SDM is SDM, but SDM is not USM or HSM or SWM. Same technology, different implementation and designs.

The point is not that the type of motor should change (ultrasonic), but the design of it (Pentax's SDM, as seen in the DA*16-50mm). Who knows, maybe the DA*60-250mm and more recent 16-50's use an "improved design" of the same technology but are still called SDM. Some seem to think that the whole issue of reliability was resolved long ago...

My only gripe about SDM is that it is dog-slow compared to the Canon ring-type USM I had on my old "L" lenses, and the HSM on my recent Sigma. I know every lensmaker has AF motors fail sometimes, while my DA*50-135mm has been problem-free for 5 years, but it's not getting any faster with age.

[kenyee]

HSM is the same type of motor as SDM so what's your point?

HSM isn't SDM. HSM is a ring motor (like what Canikon use on their fast lenses, not their primes or budget lenses).
HSM is a much bigger surface area, so it has a lot more torque/speed...

Early Sigma 70-200/2.8 HSM lenses had stuck HSM motors too, so they're not infallible...you occasionally read stories about Canikon lenses failing to focus too, but that's more rare...

[Rondec]

I guess I don't understand the discussion. In particular, I don't understand the categorization of SDM as one particular motor. Maybe it is, but I think the motor on the DA *55 is different from the one on the DA *16-50 and 50-135. Pentax can use any motor they want and call it "SDM." Hopefully over time they go to a little more powerful motor, but truthfully, if you want faster focusing, they just really need to shorten the focus throw. That is the reason that the DA limiteds are so much faster focusing than their FA limited counterparts.

[Anvh]

Sigma 17-50 HSM most likely doesn't use a ring type and the budget Nikon and Canon lenses don't use ringtype either.

For Canon search micromotor USM, that's how they call them that's the same type of motor Pentax for the SDM.

[Anvh]

I guess I don't understand the discussion. In particular, I don't understand the categorization of SDM as one particular motor. Maybe it is, but I think the motor on the DA *55 is different from the one on the DA *16-50 and 50-135. Pentax can use any motor they want and call it "SDM." Hopefully over time they go to a little more powerful motor, but truthfully, if you want faster focusing, they just really need to shorten the focus throw. That is the reason that the DA limiteds are so much faster focusing than their FA limited counterparts.

That's why i say "type" SDM stands for one type of motor.
They can't use any motor they simply want though, it needs to be a super sonic motor because that's what SDM stand for.

With TDi for example you expect to get a Turbocharged Direct Injection motor, sure it can be 200 or 600 horsepower as long as it has TDi.

[Anvh]

The point is not that the type of motor should change (ultrasonic), but the design of it (Pentax's SDM, as seen in the DA*16-50mm). Who knows, maybe the DA*60-250mm and more recent 16-50's use an "improved design" of the same technology but are still called SDM. Some seem to think that the whole issue of reliability was resolved long ago...

Pentax has said to stop designing new KAF2 lenses, that should save a lot.
So lens that has focus system like DA*16-50, DA*50-135, DA*200, DA*300 and DA*60-250 won't be make anymore.
So only KAF or KAF3, so the wel know screw-drive or build-in only not a combination of the two.
the DA*55 is KAF3 for example and does well in the test.

[Adam]

Pentax has said to stop designing new KAF2 lenses, that should save a lot. So lens that has focus system like DA*16-50, DA*50-135, DA*200, DA*300 and DA*60-250 won't be make anymore. So only KAF or KAF3, so the wel know screw-drive or build-in only not a combination of the two. the DA*55 is KAF3 for example and does well in the test.

What are you talking about? KAF lenses are limited to the F series, whereas KAF2 means screwdrive + more electronics. KAF2 doesn't necessarily

super sonic motor because that's what SDM

mean screwdrive + SDM, though they can support it (as in the big DA* zooms).

As far as SDM goes, my recommendation is that if you want fast and quiet AF, get a Sigma lens. As someone else mentioned earlier- they got it right.

[Anvh]

Adam not really and you need to think from the lens side of things.
KAF = electronic contact, auto aperture and auto focus (via drive-shaft focus)
KAF2 = KAF + power zoom (you see drive-shaft focusing and the powerzoom contacts needed for SDM although you're correct that it can also have powerzoom and not SDM)
KAF3 = KAF2 - the drive shaft (SDM only)

KF = the one for AF serries you're thinking about i believe.

The Pentax Camera Lens Compatibility Chart