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View Poll Results: Which lens?
Pentax DA 17-70mm SDM 822.22%
Sigma 17-70mm OS HSM 1027.78%
Tamron 17-50mm f/2.8 1850.00%
Voters: 36. You may not vote on this poll

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03-31-2010, 02:19 PM   #1
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17-70mm or 17-50mm?

I'm looking at getting either a Sigma 17-70mm OS HSM, Pentax 17-70mm SDM or Tamron 17-50mm f/2.8. I would get a little more reach with a 17-70, but I would gain a better low light lens with the Tamron. I can't decide.

03-31-2010, 02:51 PM   #2
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I had a DA 17-70 and the IQ was really good. I sold it only because I didn't use it enough to justify keeping it. If I had to do it over I think I might opt for the 17-50. One is 40% longer than the other, one is 1 stop faster than the other. For me the tie breaker would be the uncertainty that Pentax has ironed out all of the SDM problems. If you think that you will eventually want a longer zoom, that will take care of the focal length debate between the two.
03-31-2010, 03:03 PM   #3
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I liked the 17-70, but sold it to switch to limited primes. It was a nice lens.

The Tamron seems like a good choice, except that the bokeh is harsh to my eyes (though I've never owned one).

I don't know anything about the Sigma OS HSM. Seems like a nice addition to the Sigma line. Is it even available for purchase?
03-31-2010, 03:08 PM   #4
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I currently have the DA 17-70 and I was really surpised how much I liked the IQ and range(unfortunately it's currently having trouble locking focus above 50mm, although I don't think it's SDM related because everything below 50mm works fine).

I also have the Tamron 28-75, which I really like because it gives me the larger aperture while retaining the longer reach. Obviously I lose range on the wide end. From a practical standpoint if I could only have one lens, it would probably be neither of the ones I own and I could go with the 17-50/2.8. I would really miss the 50-75 range since it seems a majority of my shots with the Tamron end up coming in that range. That being said, you could always crop a little at 50, where as you can't really get the extra width you lose below 28.

Were you planning on keeping the 18-55 WR kit lens after you purchase the new lens?

03-31-2010, 03:23 PM   #5
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I have the DA17-70 and I am very pleased with its IQ and the range. The 17-70 stays on the K20d, and I tend to use the pancake primes in the same range more now with the K-x. I don't think I'd trade it for the 17-50, because I do use the 70mm end.
03-31-2010, 03:46 PM   #6
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I have the Tamron 17-50mm f/2.8, I say its pretty good.
03-31-2010, 03:47 PM   #7
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I have the 17-50 Tamron but have not had alot of chances to use it yet. You can only take so many pictures of snow, then someone made me get a 100-300 F4 Sigma which seems to have glued itself to my K20D ( I am really love'n that lens).
But so far the pictures taken with the Tammy seem real nice and it handles the sun really well.
I keep it on the camera while hiking and it hasn't disappointed me yet.

This picture was when I first got the lens and wanted to see how it did with the sun in it's eye. I think it's at 17mm F 9.5 and 1/350 is what my K20D picked. All I did was walk out far enough to get the sun and clicked. This is right from the camera, no pp.
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Last edited by Uncle_dad; 03-31-2010 at 04:02 PM.
03-31-2010, 05:19 PM   #8
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that's not bad, Uncle_dad. I was hoping to find someone who took exactly this kind of shot, I was wondering how it would handle full sun within the frame at the wide end.

Problem for me is I really want the 15mm Limited for landscape work - but I'm also starting up doing portraits and most of my other lenses are crap. (except for my DA 40 which is absolutely fine for portraits).

So I guess that still leaves me undecided - and actually I'm thinking for portrait work I don't need any wider than the 40, and the 18-50 isn't enough of a difference to justify actually getting it with the reasoning that "i need it to have the f/2.8 to do portraits". So I'm leaning toward a Tamron 90mm macro or Sigma 105mm macro - either would gives me a longer focal length for tighter cropped portraits, still the nice f/2.8 aperture, plus 1:1 macro capability too.

Sorry for straying off the topic! Ooops

04-01-2010, 09:09 AM   #9
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I am currently kicking around the same lenses, although not the Tammy. I had a 24-70 with my Nikon Pronea 6i (aps film slr) and miss not having that size. My other consideration is the Sigma 24-70EX f/2.8. I currently don't have a lens between 55 and 70mm.
04-01-2010, 11:24 AM   #10
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I've read many reviews and the Sigma is off my list. It's betwen the Tamron and Pentax. I like the SDM in the Pentax, but the screw drive in the Tamron gives me more security knowing that it will work five years from now. I had the USM go in a Canon lens once and I couldn't even manually focus it after that. Has anyone had any issues with SDM in Pentax lenses?
04-01-2010, 01:47 PM   #11
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this is easy, buy a Tamron 17-50/2.8 then buy a Sigma 70/2.8 prime. that solves your problem.
04-01-2010, 03:48 PM   #12
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I easily say the Tamron, it's a constant f/2.8 and at f/4 it would probably be as sharp as the Pentax 17-70 f/4 anyways.
04-01-2010, 04:00 PM   #13
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I had the Pentax 17-70mm SDM f/4 and it was a great lens, loved the focal length, loved the sharpness with good contrast; no complaints about the IQ at all - a great walkaround lens.

The SDM was a different matter, whilst I loved the silent focus, it just wasn't that snappy and not that great in low light. I also had an issue with locking focus at 17mm and eventually sent it back to Pentax for repair. When it came back, it was perfect, but by that point I had switched to Canon so sold it.

Unsure about the other two lenses, but the initial SDM woes aside, I loved the 17-70mm.
04-01-2010, 08:36 PM   #14
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Well, after more reading I decided on getting the Sigma 17-70mm OS HSM lens after all. According to's review of the Pentax 17-70,

"The main question to be asked is if there is a point of changing the kit lens 18-55 mm AL II for the tested Pentax 17-70 mm. The comparison between those two lenses’ graphs doesn’t show any big differences able to bowl you over. The results are similar, however, because the kit lens is so good, not because the Pentax 17-70 is so weak. The results for the lens stopped down by about 1 EV compared to the maximum relative aperture are very alike for both instruments. The quality difference can be only perceived wide open, where Pentax 17-70 mm fares significantly better."

I really couldn't pass up the Sigma. Look at my invoice!!!

SG1770OSAFP 17-70mm F2.8- 4 DC MACRO OS HSM For Pentax ( 668-109 / 668109 )

Product description AALOYAL:
BONUS Add to cart for Free Lens Cleaning kit !! Limited time Offer !!
Price Discount: $ -44.90

BONUS Add to cart for Free Lens Cleaning kit !!Free Item: LCK3 (QTY 1)
$ 449.00 1 $ 449.00

LOYALTY15:$15 off your order of $400 or more! (Exclusions Apply)
Price Discount: $ -15.00

Subtotal: $ 449.00

Price Discount: $ -59.90
Shipping: $ 0.00
Tax: $ 0.00
Total;: $ 389.10

Plus I get $9 back from Bing!!!
04-02-2010, 11:38 AM   #15
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I went for the DA17-70 shortly after it appeared and have not been sorry. It covers the FOV for about 85-90% of my shots. If I am going to have a zoom, it might as well be one that does not need to be changed, and it pretty much lives on the K20d body.

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