[Boris]

Hello, Forum.

Honestly - I am torn.

Pentax DA* 16-50/2.8
Pros:
* Native (as in support the manufacturer, the OEM glass is better, etc)
* WR
* Quick shift

Contras:
* SDM and focusing issues
* Expensive

Practically, if I were to err on the safe side, it means buying it brand new (think USD 1500 in local money) so as to at least have local warranty.

Sigma 17-50
Pros:
* Has OS
* Has HSM that will likely work without hiccups
* Reviews has it that it is remarkably sharp
* Cheaper than Pentax (like USD 950 in local money)

Contras:
* Not original: may flare for lack of SMC, color rendering may be questionable
* No WR, but judging from Sigma 24-60 that I have, the EX build quality is just fine

When I look at this list, it looks like Sigma should be a no-brainer. Yet, I'd like to hear what you have to say, especially if you own or owned the Sigma.

Ultimate purpose of this purchase - have a standard fast zoom to use when I am shooting on assignment/purpose/project (class of my daughter, business trips where I cannot take much gear along for obvious reasons, etc). For personal enjoyment and ultimate quality I have my Pentax primes.

Thanks in advance.

[Ash]

Lots of people in your position would be torn too.
Now that the 17-50's come on board, it's made the practical difference between the two lenses nearly insignificant.
The only reason I'd stick with the 16-50 IMO is for WR. No need for WR? Then no real need for 16-50. But it is a fine lens in anyone's language. I reserve judgement on the 17-50's IQ, build and AF performance since I've never used one. But the 16-50 is built very very well, my only gripe being a relatively slow AF. The barrel distortion at the wide end of the 16-50 can be an issue, but I don't know whether the 17-50 suffers in the same way.

[pop4]

I had to make the same choice, and chose the Sigma. SDM issues was the number factor that put me off the DA*, and at that time I had two other Sigma HSM lenses and I was very satisfied with the HSM. Price was another factor, although for me, I don't think the difference in price was as big. WR wasn't a factor for me, and I don't intend to be shooting in conditions that need WR, plus, I've used my Sigma 70-200/2.8 HSM II in light showers before, and even though it's not WR, I haven't had any issues.

[Boris]

pop4, is there a place where we can see the pics you took with Sigma?

[Chaos_Realm]

I think sigmas OS is made redundant by the in body SR
But then the HSM I have Found to be significantly quicker than SDM. (on the sig 70-200)

As ash said the only reason I would go for the pentax is for WR

[Boris]

Chaos_Realm, without going into detailed comparison of OS vs SR (it really belongs in a different topic), to have the flexibility to switch between the two ought to have certain value.

[Chaos_Realm]

Chaos_Realm, without going into detailed comparison of OS vs SR (it really belongs in a different topic), to have the flexibility to switch between the two ought to have certain value.

Fair enough, I personally wouldn't see the need for it. But if that is a feature you wish to weigh in on your decision then certainly do so. I don't know advantages of OS vs SR as I've never shot with it.

[pop4]

pop4, is there a place where we can see the pics you took with Sigma?

There's not much and the selection doesn't really highlight the abilities of the lens, but try here: http://www.flickr.com/groups/1449225@N25/pool/34685004@N00/
There's also a lot of shots here, but they include photos from all different mounts of this lens, not just k-mount: Flickr: The Sigma 17-50mm F2.8 EX DC OS HSM Pool

[rvannatta]

I have been a long term user of the DA* 16-50 which is now on it's 3rd digital body. Like every lens you have to get used to it, but I consistently have taken most of my photos with it.

[civiletti]

I believe the Sigma has higher IQ.

[agsy]

Fair enough, I personally wouldn't see the need for it.

Why not go with the Tamron 17-50? Cheaper and smaller than the Sigma but without OS and HSM. Great IQ however.

[calicojack]

Since you already have the sigma 24-60, why not supplement it with a DA 12-24 or similar?

[Boris]

pop4, thanks' for the links. I will certainly review the pictures taking my time.

rvannatta, thanks!

civiletti, could you please elaborate on that?

calicojack, well, you see, 16/17 mm is wide enough for me. And given the potential usage pattern of this lens, I may not be able to swap between 12-24 and 24-60. In other words, I am not looking to cover super-wide angle. Ideally 20-70/2.8 would be my perfect optic. But 16(17)-50 will do just as nicely.

[Jewelltrail]

1st Choice: Buy the Tamron 17-50 f/2.8

2nd Choice: Buy the Sigma 17-50 f/2.8

Tamron is best choice for wide open, and amazingly sharp throughout the entire range. Only thing the 16-50 has going for it is the WR, which is not needed. I took the Tamron, for 3 years, up and down mountains of Maine, New Hampshire & Vermont in alll 4 seasons of the year--no problems, I sold it after 3 years to help fund a full-frame kit & it still looked and performed like new--after 15,000 shots.

[civiletti]

pop4, thanks' for the links. I will certainly review the pictures taking my time.

civiletti, could you please elaborate on that?

I compared results from Photozone's tests - not directly, but by calculating conversion factors for the various camera's they have used to test lenses. The Sigma 17-50/2.8 bested all Pentax normal zooms in MTF scores. The Tamron 17-50/2.8 scored even higher than the Sigma, though the Sigma may focus more quickly. I recently bought a Tamron to evaluate versus my prime lenses in tripod-mounted landscape work. The numbers suggest it can match, at optimum aperture, all but a few prime lenses [like the Zeiss 28mm/2 and Nikon's newer 50mm/1.4].