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02-13-2012, 01:11 PM   #1
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55-300 on K-x vs K-5? also, 17-70 vs 18-135

I am trying to convince myself to get a K-5 (have K-x right now, feels a bit too simple after some use)

Can anyone tell me if 55-300 works better with K-5 autofocus system? Or the same? Does it search as much? Can it focus from fully unfocused without doing a few full runs? Although I now utilize QS fully before actually using AF with this lens, it kind of helps but I could use more good shots... Will I be surprised after upgrading to K-5?

Also, I am thinking to get a SDM lens for K-5 to truly use the new AF. I wanted 18-135 but the optical quality does not seem to be good enough. So I am thinking, will 17-70 be better choice? Is its SDM motor as fast as 18-135's? Is it worth getting it instead of 18-135? I don't really care about long end since I will probably use 55-300 for anything longer than 70 anyway...

02-13-2012, 01:27 PM   #2
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The AF on the K-5 is more accurate, so yes, you should get better performance and less hunting. It won't be faster in the sense that it moves the lens faster, but it'll definitely be more precise.

The AF on the 18-135mm is pretty much unmatched by any other SDM lens, so if you want AF speed, that's the way to go. If you want a quality walkaround, though, I would go for the Tamron 17-50mm. The 17-70mm is fine, but the SDM does have a tendency to fail (whereas the Tamron has screwdrive AF and the 18-135mm does not fail as far as we can see).

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02-13-2012, 03:40 PM   #3
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Even the screwdrive on the K-5 is pretty quiet, and it's faster than SDM. I think Adam's suggestion of the Tamron 17-50 is a good one. I have the Tamron 28-75 and I am very happy with it.
02-13-2012, 04:32 PM   #4
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QuoteOriginally posted by kenafein Quote
Even the screwdrive on the K-5 is pretty quiet, and it's faster than SDM.
Sorry for the blunt question but how do you know that, since i don't know how you can test that?

02-13-2012, 06:53 PM   #5
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QuoteOriginally posted by Anvh Quote
Sorry for the blunt question but how do you know that, since i don't know how you can test that?
I had a K-5 and a K-7 before. I returned the K-5 for a faulty AF system, but they were both luxuriously quiet compared to my K100D and my K-r, and even the K20D.
02-14-2012, 03:44 AM   #6
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QuoteOriginally posted by Adam Quote
The AF on the K-5 is more accurate, so yes, you should get better performance and less hunting. It won't be faster in the sense that it moves the lens faster, but it'll definitely be more precise.
The K-5 screwdrive is actually faster than the K-x screwdrive. So yes, the K-5 will move the 55-300 faster than the K-x.

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--Anders.
02-15-2012, 06:35 PM   #7
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I don't have a K-x, but I'm wondering if the K-x screw drive (and that of other AA bodies) might be slower than it otherwise might be due to the type of batteries (usually) employed, whereas battery type isn't an issue with a K5.

Paul
02-15-2012, 06:46 PM   #8
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Just want to add the 17-70 doesn't seem to has the history of complaints other SDM lenses have had so don't dismiss it out of hand. I have a Sigma 17-70 (I couldn't afford the Pentax) and the focal length is awesome.
With the 55-300 get the DA over the DAL version, the quickshift makes all the difference. I have the DAL for my Kx and K7 and it is annoying if you miss the focus as hunts all over the place. Fantastic lens.

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