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10-25-2017, 06:06 AM   #1786
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QuoteOriginally posted by Franc Quote
its sdm not dc?
Good catch. Seems odd to call it that.

10-25-2017, 06:07 AM   #1787
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QuoteOriginally posted by JPT Quote
This looks exactly like the mock-up shown at CP+ in February. No changes to the overall barrel shape or detailing. Apologies for the poor image. I really wasn't concentrating at the time.

Then . . .


and now . . .
Ya, but everyone in the thread says Pentax doesn't release any information.
10-25-2017, 06:11 AM   #1788
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QuoteOriginally posted by JPT Quote
This looks exactly like the mock-up shown at CP+ in February. No changes to the overall barrel shape or detailing. Apologies for the poor image. I really wasn't concentrating at the time.

Then . . .


and now . . .
The finish of the casing is smoother, the lettering is now engraved, the depth-of-field scale is an actual one and, last but not least, the piece of black tape is gone!
10-25-2017, 06:13 AM   #1789
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QuoteOriginally posted by pres589 Quote
Good catch. Seems odd to call it that.
My understanding is SDM is a small electric motor that drives a gear, like screw drive with an internal motor. DC is a ring motor, PLM is a stepper motor. But I would also expect each SDM motor for each lens is specific to that lens. Surely they aren't one size fits all?

And yes, I called you Shirley.

The DFA 1.4, my guess is it's portrait/ wedding lens. Unless you're planning to do full body contact high speed weddings SDM is probably adequate. You don't need your most expensive fastest lens on every lens.

10-25-2017, 06:14 AM   #1790
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The DoF scale is steeper.
Attached Images
 
10-25-2017, 06:15 AM   #1791
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QuoteOriginally posted by Mistral75 Quote
Do you remember what I wrote here in September?
yes, but why call it SDM? On this forum it's not well received. I don't mind, mine is still working without any hassle. On the newer lenses it's a DC engine.
10-25-2017, 06:18 AM - 1 Like   #1792
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QuoteOriginally posted by Mistral75 Quote
The finish of the casing is smoother, the lettering is now engraved, the depth-of-field scale is an actual one and, last but not least, the piece of black tape is gone!
Those are big improvements.

---------- Post added 10-25-17 at 09:19 AM ----------

QuoteOriginally posted by Franc Quote
yes, but why call it SDM? On this forum it's not well received. I don't mind, mine is still working without any hassle. On the newer lenses it's a DC engine.
This forum should get over it.

There's a lot of things this forum should get over.

I'm curious, why would I buy the 50 1.4 instead of the 55 1.4? After all, a longer lens with the same aperture gives you more control of DoF? What do you suppose is the reason they made this so big?

Is there some thing going on in the market where people think given a smaller lens and a bigger lens, people should always buy the bigger one? This looks like the Sigmatization of Pentax.
10-25-2017, 06:20 AM   #1793
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QuoteOriginally posted by normhead Quote
This forum should get over it.
There's a lot of things this forum should get over.
can't agree more

10-25-2017, 06:21 AM   #1794
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QuoteOriginally posted by Franc Quote
yes, but why call it SDM? On this forum it's not well received. I don't mind, mine is still working without any hassle. On the newer lenses it's a DC engine.
SDM lenses which are Tamron rebadged lenses have a ring motor (USD in Tamron's jargon). All other SDM lenses have a micromotor or, rather, had: until this one. All DC lenses also have a micromotor. Don't look for much logic in there.
10-25-2017, 06:23 AM   #1795
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SDM is any kind of piezo ("ultrasonic") motor, be it a micromotor or a ring-type motor.
Canon is using the USM designation in a similar manner.
10-25-2017, 06:27 AM   #1796
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QuoteOriginally posted by normhead Quote
I'm curious, why would I buy the 50 1.4 instead of the 55 1.4? After all, a longer lens with the same aperture gives you more control of DoF? What do you suppose is the reason they made this so big?
The DA55 ist almost perfect on an APS-C sensor, but it is probably not good enough (for the pixel peeper) on full frame.
It seems that you have to be that big to get near perfection on FF.
10-25-2017, 06:31 AM   #1797
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QuoteOriginally posted by Mistral75 Quote
SDM lenses which are Tamron rebadged lenses have a ring motor (USD in Tamron's jargon). All other SDM lenses have a micromotor or, rather, had: until this one. All DC lenses also have a micromotor. Don't look for much logic in there.
I guess that's a fault of mine.
But I did read somewhere once that there was a difference between SDM and DC.
10-25-2017, 06:33 AM   #1798
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QuoteOriginally posted by normhead Quote
I guess that's a fault of mine.
But I did read somewhere once that there was a difference between SDM and DC.
Indeed there is one: the failure rate .
10-25-2017, 06:35 AM   #1799
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QuoteOriginally posted by normhead Quote
I'm curious, why would I buy the 50 1.4 instead of the 55 1.4?.
Quicker focus, sharper and better suited for K-1's brilliant sensor? 55 1.4 is ok, but useless for many pros
10-25-2017, 06:51 AM   #1800
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QuoteOriginally posted by Mistral75 Quote
Indeed there is one: the failure rate .
Maybe. But not all SDM lenses are created equal. The DA *200 and 300 and 55 lenses seem to have failure rates that are similar to the DC motor lenses -- they do happen, but there aren't frequent reports of them, while the DA *16-50 and 50-135 have higher rates (now fixable with change to screw drive mode).

Since the motors differ from lens to lens, it is hard to know what to make of the designation. The Tamron produced 24-70 and 15-30 both are listed as SDM lenses, even though they aren't even made by Pentax. It's just what Pentax calls a certain of motor. It doesn't mean unreliable (or reliable).
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