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08-28-2014, 04:55 AM   #871
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QuoteOriginally posted by Alizarine Quote
I think this one will be difficult given that it can be a fairly large lens with many elements. The 18-270 rebadge from Tamron could've gotten a DC motor but they opted for SDM; on the other hand the DA 560 f5.6 only has 6 in 5 groups, so maybe that's why it still got a DC motor.
The DA 18-135 has 13 elements / 11 groups and yet has a DC motor.

08-28-2014, 05:59 AM   #872
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QuoteOriginally posted by Alizarine Quote
I think this one will be difficult given that it can be a fairly large lens with many elements. The 18-270 rebadge from Tamron could've gotten a DC motor but they opted for SDM; on the other hand the DA 560 f5.6 only has 6 in 5 groups, so maybe that's why it still got a DC motor.
IMO it is much more simple (alas), they just went with what Tamron builds.
I'm pretty sure the motors are the Tamron motors. No QuickShift, guess why?
08-28-2014, 06:37 AM   #873
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The quickshift is merely a friction clutch between the AF drive and focus mechanism, nothing more. Unless the Tamron motor is significantly sensitive to back resistance, it shouldn't itself preclude its use with a quick-shift design. It might, however, require a slight enlargement of the barrel to accommodate the clutch, which, to be fair, would be an additional expense.

QuoteOriginally posted by thibs Quote
IMO it is much more simple (alas), they just went with what Tamron builds.
I'm pretty sure the motors are the Tamron motors. No QuickShift, guess why?
08-28-2014, 06:47 AM   #874
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QuoteOriginally posted by IchabodCrane Quote
The DA 18-135 has 13 elements / 11 groups and yet has a DC motor.
point taken, thanks. That lens is a lot smaller than the 18-270 though.

QuoteOriginally posted by thibs Quote
IMO it is much more simple (alas), they just went with what Tamron builds.
I'm pretty sure the motors are the Tamron motors. No QuickShift, guess why?
You mean the PZD motors on the Tamron version?

08-28-2014, 06:49 AM   #875
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QuoteOriginally posted by Alizarine Quote
point taken, thanks. That lens is a lot smaller than the 18-270 though.


You mean the PZD motors on the Tamron version?
yep.

Pentax 18-250 didn't have QS either AFAICT. Coincidence? I don't think so.

EDIT
There's no point in a rebadge if you need to mod the lens before selling it.
I don't believe either that SMC is SMC if you see what I mean (unless Tamron licensed SMC from Pentax that would be funny enough)

If you want to mod an existing design, you take the blue print you do the rest. That was what Pentax and Tokina did.
08-28-2014, 11:09 AM   #876
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QuoteOriginally posted by Alizarine Quote
I think this one will be difficult given that it can be a fairly large lens with many elements. The 18-270 rebadge from Tamron could've gotten a DC motor but they opted for SDM; on the other hand the DA 560 f5.6 only has 6 in 5 groups, so maybe that's why it still got a DC motor.
There a 17-70 f/4. It has SDM & quick shift. HD-55-300 WR showed that adding seals and changing coating doesn't require a design change. So we are speaking of starting at 16mm. Likely you could do that while keeping the 17-70 design.

WR would be quite nice on this lens and help differentiate from sigma offering (17-70 f/28-4). I would not really care of pushing 16mm instead of 17... But it would be interresting to increase picture quality a little bit. The 17-70 is good, but not really better than 18-135 on same range.
08-28-2014, 11:34 AM   #877
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QuoteOriginally posted by Nicolas06 Quote
WR would be quite nice on this lens and help differentiate from sigma offering (17-70 f/28-4). I would not really care of pushing 16mm instead of 17... But it would be interresting to increase picture quality a little bit. The 17-70 is good, but not really better than 18-135 on same range.
I disagree, the DA 17-70 is a much better lens than the 18-135:

Pentax Lens: Zooms - Pentax 18-135mm f/3.5-5.6 ED AL [IF] DC SMC DA WR (Tested) - SLRgear.com!

QuoteQuote:
Pentax 17-70mm /4 AL IF SDM SMC DA ~$600
It may not provide the same telephoto reach of the 18-135mm, but it is a much sharper lens, complete with a consistent /4 aperture across its focal range. It also has its issues with chromatic aberration
They cost about the same price but the rendering and sharpness out of the Pentax version is excellent. Can't speak to the Sigma.
08-28-2014, 12:04 PM   #878
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QuoteOriginally posted by philbaum Quote
I disagree, the DA 17-70 is a much better lens than the 18-135:

Pentax Lens: Zooms - Pentax 18-135mm f/3.5-5.6 ED AL [IF] DC SMC DA WR (Tested) - SLRgear.com!



They cost about the same price but the rendering and sharpness out of the Pentax version is excellent. Can't speak to the Sigma.
i tested both in hand. I own the 17-70 and my father own the 18-135.

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