[FantasticMrFox]

That example with the double edges is atrocious. I have not seen anything remotely like that in a year of usage. CA performance has been exemplary. Generally Sigmas excel in controlling CA, even with their humbler lenses. I have to wonder whether your 17-50mm is defective.

I am wondering the same

My first day with the Sigma 17-50mm was a year ago. I don't see fringing or CA in these harsh conditions.

Sit down, let me take you on a trip to CA country Screenshots from LR with CA correction off - first the whole image, then the 1:1. We're talking about 5 px in width with the big central purple one.

And that's the thing - I have a lot of images like yours where I see very little CA even in harsh light, but then I get some like these that are just horrible. Same with the focusing, and the double edge bokeh. It's so inconsistent I may well send it in to Sigma with a complaint, and the Sigma guys would take a bunch of test images and wonder what the hell I'm on about Thankfully the normal images far outnumber the bad ones.

Attached Images

   

[audiobomber]

I may well send it in to Sigma with a complaint, and the Sigma guys would take a bunch of test images and wonder what the hell I'm on about

The blurriness in the crop is unusual as well. My copy is prime sharp, and I am not exaggerating. You should send yours to Sigma, and email them a few bad images.

[papillon_65]

I have the Sigma 17-50mm F2.8, the 16-85mm and the 20-40mm F2.8-F4. My experience of them is as follows:

Sigma 17-50mm F2.8
My copy of this lens is brutally sharp, and I mean sharp, it behaves exactly as the better reviews say. It's sharp wide open at both ends but unusually for a lens of this type, it's sharpest at the long end. Mine is also a bit of an erratic focuser in low light, much better in good light. The build quality is very good and it feels much better built than your average Tamron. The Sigma does have a bit of clinical look to it, but you can get great results with it no problem. If you're looking for a sharp lens this is the one to get, it's prime sharp stopped down, sharper than plenty of primes in fact. For the money it's an excellent lens.

Pentax 16-85mm
This is also a sharp lens, especially at the wide end and it's sharp wide open throughout it's range. It's not as sharp as the Sigma but that's an exceptionally sharp lens as I've said. The 16-85mm is also a quick and reliable focusing lens, and has nice colour and contrast. On my K3II this lens is also good for C-AF track focusing in good light, I was pleasantly surprised by it's performance. It also focuses quite closely, so with a close-up lens you can do semi-macro with it. If you want a lens for its versatility then this is the one to get.

Pentax DA 20-40mm Ltd
This one is a bit of a mixed bag, mine is a bit erratic focusing wise, but it's capable of excellent results. It's very sharp in places, not so in others. It definitely benefits from stopping down. In its favour is that it is just a lovely piece of engineering, it looks great and is lovely to use. It also has the classic DA Ltd rendering and is very flare resistant. It's most definitely in the DA Ltd mold, quirky and a lens you can learn to love. It makes a great combination with the 15mm and 70mm DA Ltd's and I use it with these on my K-01.

I don't know about the Tamron or the 16-50mm, but out of the lenses I have I'd pick the Sigma if ultimate image quality and speed was important, the 16-85mm as a general slower workhorse and the 20-40mm because....well...it's just one of those lenses that has character. Personally I'm tempted to try the DA* 16-50mm, I've just received my DA* 60-250mm and boy is that a nice lens, so the 16-50mm is calling to me now, but it will have to be very good for me to give up the Sigma 17-50mm, that lens is the sharpest zoom of this type I've ever used, when you nail a shot with it then it's brutal, if sharpness is your thing it's a no-brainer.

[peterh337]

I had the 16-85 on a K3 for over a year and it is an outstanding lens.

Now, with a K1 and 24-70 f2.8 weighing 1.8kg I miss that combo. I did 99% of my shooting with it. Unfortunately there doesn't appear to be a zoom with a similar range and performance for a FF camera, which is not surprising.

[Scorpio71GR]

I had the 16-85 on a K3 for over a year and it is an outstanding lens.

Now, with a K1 and 24-70 f2.8 weighing 1.8kg I miss that combo. I did 99% of my shooting with it. Unfortunately there doesn't appear to be a zoom with a similar range and performance for a FF camera, which is not surprising.

The closest on the K1 is the DFA28-105. It is an outstanding lens. I have only used it on the K3 so far. On a APS-C the 16-85 has an equivalent field of view of 24-119mm. You are losing 4mm on the wide end and 14mm on the long end with the 28-105 on the K1.

[audiobomber]

The closest on the K1 is the DFA28-105. It is an outstanding lens. I have only used it on the K3 so far. On a APS-C the 16-85 has an equivalent field of view of 24-119mm. You are losing 4mm on the wide end and 14mm on the long end with the 28-105 on the K1.

A K-3 or K-70 with Sigma or Pentax 17-70mm f4 is a pretty good comparator to a K-1 and 28-105 f3.5-5.6.

[Marcus_H]

So I think I've decided on the 16-85. They all look like really great lenses, but the WR sealed the deal for me as I shoot mostly outside. I'll post some images once the lens arrives and I have some time to play with it.

Thanks for all the insight and happy new year!

[Scorpio71GR]

So I think I've decided on the 16-85. They all look like really great lenses, but the WR sealed the deal for me as I shoot mostly outside. I'll post some images once the lens arrives and I have some time to play with it.

Thanks for all the insight and happy new year!

I just picked one up in the Marketplace. So far I have been impressed. Tomorrow is supposed to be somewhat sunny, not too common here in the winter, hopefully I can get some shots in.

[timb64]

Marcus and Scorpio,enjoy your new lenses and post some pics here

https://www.pentaxforums.com/forums/10-pentax-slr-lens-discussion/301618-da-1...can-do-33.html