[AlwaysAl]

I have one purchased for wide angle close up with less than perfect light situations and I'm satisfied. This was purchased prior to the K-3iii and, at the time, a little pricey. For a time, it was a go-to lens, very versatile but more recently with the K3iii the role has seemingly evolved to the 50-135.

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[PocketPixels]

Get the older version. It’s not a dog and there’s one in the marketplace for under $350 with working sdm if I remember accurately.

Also there are two 3rd party 17-50 f2.8 alternatives.

Bingo. Get the Sigma 17–50mm ƒ/2.8. It's sharper than the mark I DA★ and has quiet and reliable HSM focusing mechanism. It does not have weather sealing, but a good used copy can be had for under $300. I own one and really like it.

[Des]

The 20-40 is definitely a contender! I have the 18-135, but it's just a bit under powered in indoor settings.

I have both, plus in that range the DA 16-85 and DA 35 f2.4. (I also have the FA 43 Ltd.) Each has its place, but the 20-40 Limited has that something special. In terms of sheer resolution, the humble plastic fantastic is sharper, but the 20-40 is quite sharp, if you can live with the field curvature. And it's beautifully built and quite compact and lightweight. But if you need the wider aperture (e.g. for astro), there no substitute for the Sigma 18-35.

[Digitalis]

Bit of a dark horse given the mixed feedback on autofocus, have to imagine the better AF of the K3iii would help it out?

I tried the Sigma 18-35mm f/1.8 ART on a number of camera bodies: from the K10-K7-K5IIs-K3II-K1 and KP, all cameras experienced varying degrees of inconsistent AF lock results with my copy of the lens. The K-1 and KP would hunt more but eventually would lock focus (the old K10 would just give up after two cycles and typically misfocus on both attempts) though the gap between infinity and 1.8m was always problematic. So it is possible the K3III may be better, as always YMMV. No camera I have used this lens on could obtain 90% reliable AF locks*, even under controlled conditions.


It is with many reservations I'd suggest getting this lens, but I assume you are reasonably comfortable with manual focusing: If you do get the 18-35mm f/1.8 ART get it with the lens dock, as in camera AF calibrations with 3rd party lenses won't be as accurate as dedicated calibration solutions.




AFAIK there isn't any firmware that expressly addresses the inconsistencies with AF for this particular lens.

*Tested with Datacolor Spyderlenscal, focused with Phase AF, tested 10 times each with the lens set to either minimum or ∞ focus, live view contrast AF was more accurate, but slower especially when starting from MFD.

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Last edited by Digitalis; 11-03-2021 at 02:58 AM.

[Papa_Joe]

Bingo. Get the Sigma 17–50mm ƒ/2.8. It's sharper than the mark I DA★ and has quiet and reliable HSM focusing mechanism. It does not have weather sealing, but a good used copy can be had for under $300. I own one and really like it.

To name the second alternative, which I belive is still available new: Tamron 17-50/2.8. IQ is a bunch of primes, if you get a good one. Built quality is mediocre, but it is small and lightweight. It is slot driven, but fast and (mine at least) most time on spot. It worked on my istD*, K-10D and now K-70 to my full satisfaction.

Sure the Sigma 18-35 has better IQ and built quality, but you can try a used Tami for a fraction.

[cxdoo]

To name the second alternative, which I belive is still available new: Tamron 17-50/2.8. IQ is a bunch of primes, if you get a good one. Built quality is mediocre, but it is small and lightweight. It is slot driven, but fast and (mine at least) most time on spot. It worked on my istD*, K-10D and now K-70 to my full satisfaction.

Sure the Sigma 18-35 has better IQ and built quality, but you can try a used Tami for a fraction.

To name the second alternative, which I belive is still available new: Tamron 17-50/2.8. IQ is a bunch of primes, if you get a good one. Built quality is mediocre, but it is small and lightweight. It is slot driven, but fast and (mine at least) most time on spot. It worked on my istD*, K-10D and now K-70 to my full satisfaction.

I used this lens for many years as general purpose zoom.

Upsides:
* dirt cheap for what it provides
* very sharp
* light
* reasonably fast to focus

Downsides:
* poor build quality. After 10 years mine has pretty much fallen apart.
* very flat rendering, both in color and OOF transition
* significant distortion on wide end
* not weather sealed

In summary, it's a very sharp lens for low cost, which will show signs of wear and tear after several years of heavy use and rarely provide rich and striking images. Overall, worth the cost.

[gatorguy]

I'm really interested in this lens for the K3iii. Bit of a dark horse given the mixed feedback on autofocus, have to imagine the better AF of the K3iii would help it out? Anyone tried this combo? I'm looking for a fast zoom lens for covering indoor events, I'm thinking either this or the new 16-50 would be good.

Personally I'm good with the Sigma 18-35 on the K3III. As Uncle Vanya said, if I need the wider aperture there's not much for options. Is the keeper rate as good as the new 16-50? Absolutely not, and the Pentax focuses a LOT faster. For my stage/event stuff I still carry the 18-35. Focus is reliable enough.

[mctaveck]

I had something less then 500 shots with that lens , focusing seem really accurate. I had a session at the circus (low light, subjects moving etc) and even at 1.8 i miss really few
Danilo