Have Sigma 17-70, worth adding Pentax 16-45 ?
you may find one more usefull than the other for some shots, and may well be able to post a "Shoot-out" test for us!
I find the 16-45 gets straight lines straight, and focusses real close, and really doesn't fall off at the corners to any noticable degree...
I don't have the sigma, but tried one out at a camera store (used older model), it seemed loud, hunted a fair bit, and lots of purple fringing on high contrast edges. (caveat emptor... I've incorrectly used pf in the past as a blanket phrase for several different types of chromatic abberations... I don't care what specifically it is, the sigma appeared worse than the pentax when shooting tree branches through a window, at the store on that particular day... so I bought a Pentax... ok?)
Fired many shots. Didn't kill anything.
I just bought it, and I am stunned every time I look at a photo I've taken. Completely superior to any other zoom I have ever tried (and i am no exaggerating) and probably comparable to a good prime lens on many apertures. And the issues about quality have been solved long ago, not to mention that you would want to buy from a UK store, with warranty, and eventual immediate replacement for any inconvenience. The lens is absolutely amazing.
Hope this helps.
'Between the lights there is always a shadow'
www.nathanservi.com & PPG
Just because you mentionned it. If you have to upgrade from anything better than a 18-55, in my opinion you have to go for the DA* 16-50mm.
I just bought it, and I am stunned every time I look at a photo I've taken. Completely superior to any other zoom I have ever tried (and i am no exaggerating) and probably comparable to a good prime lens on many apertures.
And there I was, thinking that I was more or less sorted, lens-wise.
If the QA questions really have been laid to rest, it's the next on my list.

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Pentax K-3, DA18-135, DA35 F2.4, DA17-70, DA55-300, FA28-200, A50 F1.7, A100 F4 Macro, A400 F5.6, Sigma 10-20 EXDC, 50-500 F4.5-6.3 APO DG OS Samsung flash SEF-54PZF(x2)
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Having said all this I am very pleased with the Sigma 17-70 & I'm starting to think that a wider option would make more sense..the
Sigma 10-20 or Pentax 12-24, both of which would give less distortion too around the 14/15mm foacal length
simon
My website http://www.landscapephotographyuk.com
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simonkit
Member
Mold, North Wales
I already have the Sigma 17-70 which I find excellent & have been watching the new Pentax 17-70 comments with interest, initial impressions don't seem too exciting... the DA 16-50 isn't much dearer but this seems to have lots of quality issues so deters me too.
The 16-45 lenses are dropping in price now & I wondered if it might be worth owning both the Sigma & the 16-45 ?
simon
My website http://www.landscapephotographyuk.com
My Facebook page http://www.facebook.com/landscapephotographyuk
Find me on Google+ link