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09-12-2012, 02:17 AM   #46
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QuoteOriginally posted by Catalana Quote
LOL, if that was the case, we'd have the "perfect system". From your statement above, you imply that Pentax has some form of quality control a step above Tamron's. Maybe two decades ago.., but Pentax's own SDM is so bad, they have to re-brand another technology as their own (tongue in cheek). Even then they are still unable to offer an equivalent warranty (6 years versus 1 year) . If their marketing department can spin the specs of their new flagship camera, I'll take a stab at their lenses. Shenanigans, as someone mentioned before, albeit for the "new" focusing system on the K-5II ..
No, I didn't imply that. There's an enormous difference between applying your own "quality control" system (an abused term, and a concept superseded decades ago in Japan by Quality Management and its successor extensions) to someone else's product and using your supplier's own system to separate out those products that fall within a narrower tolerance band. I wouldn't expect anyone not involved in manufacturing to understand the finer details, though.

One of the probable reasons Tamron can sell product at a lower price is that it accepts a greater variation in optical precision than other makers. That's one reason Zeiss and Leica lenses cost more. It doesn't mean that the quality of Tamron is less, it just means that the standard applied is different in that regard. If you look at the manufacturing definition of "quality" it doesn't equate to "standard", so you should really understand how others understand terminology before you break into derisive laughter.

I would hope that the SDM problems caused Pentax to review its piezo motor supplier's standards, but we will probably never know, until new product under that banner proves itself, or otherwise.

09-12-2012, 04:10 AM   #47
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QuoteOriginally posted by Docrwm Quote
They license the well thought of Tamron 18-270. Good.
.
It's not fair play. IMO.

To put not strong optically (i'd say weak)
http://www.photozone.de/nikon--nikkor-aps-c-lens-tests/716-tamron182703563pzd?start=1
super-zoom into Pentax body + bad reputation SDM and ask USD800....
09-12-2012, 04:13 AM   #48
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QuoteOriginally posted by liukaitc Quote
I think the bad reputation mainly from 16-50 and 50-135. seems those prime like 55mm, 200mm, 300mm or 60-250 do not have bad reputation.
Wrong. The same with 60-250 and 55.
09-12-2012, 09:40 AM   #49
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QuoteOriginally posted by Docrwm Quote
Why not avoid the baggage associated with "SDM" and just call it "DC"?
I've already said this 4 times already.

SDM = works by friction, it's an ultrasonic engine
DC = an electric magnetism engine

here pictures.
SDM (ultrasonic engine.)


DC (electro engine), the coloured parts are magnets.


Clear now?


Last edited by Anvh; 09-12-2012 at 09:47 AM.
09-12-2012, 10:04 AM   #50
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QuoteOriginally posted by Anvh Quote
I've already said this 4 times already.

SDM = works by friction, it's an ultrasonic engine
DC = an electric magnetism engine

here pictures.
SDM (ultrasonic engine.)


DC (electro engine), the coloured parts are magnets.


Clear now?
In other words, you can't call it DC because that would be a lie.
09-12-2012, 10:40 AM   #51
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Preciesly.

You can not call a diesel engine a petrol engine right, Nikon does it though...
09-12-2012, 10:45 AM   #52
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QuoteOriginally posted by Anvh Quote
Preciesly.

You can not call a diesel engine a petrol engine right, Nikon does it though...
Seems like they should just work on improving DC motors then. Surely if they're tweaked enough, they'd eventually be as fast as HSM/SDM/PZM style AF systems.(And more reliable it would seem.)
09-12-2012, 10:49 AM   #53
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QuoteOriginally posted by Eulogy Quote
Seems like they should just work on improving DC motors then. Surely if they're tweaked enough, they'd eventually be as fast as HSM/SDM/PZM style AF systems.(And more reliable it would seem.)
Well, they're louder too. Seems like they should work on improving the SDM motors since they are the ones that fail.

09-12-2012, 10:52 AM   #54
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QuoteOriginally posted by vonBaloney Quote
Well, they're louder too. Seems like they should work on improving the SDM motors since they are the ones that fail.
I hardly notice the difference in sound between my 18-135, and my girlfriend's 28-135(Canon) or her 50 1.4.

All motors make noise, the DC just makes a humming noise(Electromagnets I suppose?) versus the sliding sound of the HSM.

Just saying...DC seems more reliable, as all HSM designs have failures at times.(Canon, Nikon, Sigma and Tamron lenses do have motor failures, they just have less overall)

Edit: And if noise is really an issue, they could probably engineer a way to reduce it.(If 6dB of noise makes anyone uncomfortable...personally, I like my old screw driven lenses when the go "Clack!"...sounds faster :P)
09-12-2012, 11:05 AM   #55
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QuoteOriginally posted by Eulogy Quote
Seems like they should just work on improving DC motors then. Surely if they're tweaked enough, they'd eventually be as fast as HSM/SDM/PZM style AF systems.(And more reliable it would seem.)
Well Pentax don't make these engines but they buy them.

This the answer why SDM is the way forward and not DC.
QuoteQuote:
Electromagnetic motors were invented more than a hundred years ago. While these motors still dominate the industry, a drastic improvement cannot be expected except through new discoveries in magnetic or superconducting materials. Regarding conventional electromagnetic motors, tiny motors smaller than 1 cm3 are rather difficult to produce with sufficient energy efficiency. Therefore, a new class of motors using high power ultrasonic energy—ultrasonic motors—is gaining widespread attention. Ultrasonic motors made with piezoceramics whose efficiency is insensitive to size are superior in the mini-motor area.
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