Standard zoom, which one?
I have the DA*16-50mm but take the 18-135mm when out walking, for outdoor use the 18-135mm is a great lens.
The 18-135mm will cost less and is a very, very useful lens. I use it perhaps 95% of the time.
Best regards, John
Phil
K-5iiS; K-r; ME Super; ME; DA* 16-50 f2.8; DA 18-135 WR; DA 55-300 WR; HD DA 15mm F4 ED AL Limited; FA 50mm f1.4; A50mm f1.7; DAL 18-55mm; M40mm f2.8; + assorted non-Pentax lenses
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However, I recently bought a Sigma 17-50 f2.8 OS and it's in a totally differnt league. Build quality, IQ, everything. At present prices seem to be at their lowest around £279.
Worth reading this comparison: http://www.pentaxforums.com/reviews/pentax-16-50-vs-sigma-tamron-17-50mm/introdu...
I have a 17/70 Pentax and love even though it is a little sloppy in the rings but don't let that put you of it is fast at focusing and takes a dam good photo
https://www.pentaxuser.com/forum/topic/should-i-buy-the-pentax-18-135mm--------5...
If they have one on the Pentax stand at the Photography Show and I like it, I'll buy it.
6th Year Apprentice Pensioner

I have taken some good shots with it and can recommend it.








But, on reflection, I was unfair to the lens. I have taken (slightly) technically better photos using other lenses, but the shots that are my favourites are almost invariably from the 17-70. The photo below was taken using a 17-70, and I reckon it shows the quality this lens is capable of delivering.
link
Regards, Christopher
ChristopherWheelerPhotography

And if you want a fair priced S/H one for £159 then Chiswick Cameras have one...
http://chiswickcameras.co.uk/products/pentax-18-135mm-f3-5-5-6-ed-al-if-dc-wr-le...
No Connection or vested interest

LennyBloke
I've got a 16-45 and I'm a big fan. It gives great results and was on my camera most of the time.
However, I recently bought a Sigma 17-50 f2.8 OS and it's in a totally differnt league. Build quality, IQ, everything. At present prices seem to be at their lowest around £279.
Worth reading this comparison: http://www.pentaxforums.com/reviews/pentax-16-50-vs-sigma-tamron-17-50mm/introdu...
How does the sigma 17 to 50 compare with the tamron?
Both are f2.8 wonder why the sigma is more expensive...
In answer to the op the 18-135 is a great walk about lens although I haven't used mine since I got the 16-85 in December....this gives better results.
Only got the Tamron f2.8 last week as I shoot a lot of darkish events and want to try with a faster lens no results to compare in detail but the few general shots I have taken have all been fine.
There's such a wide choice of zoom and speed that it really depends on I our budget and primary uses.
Cheers,
Bruce
Mine is a solid performer, even wide open in poor light. It's the one I choose for astro and sometimes weddings and events if I need to be adaptable, but the photos don't exactly jump out at me. I don't think I have any that I would consider exeptional, but I think the same could be said of any of the other zooms and if I need that sort of quality, I put a prime on.
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Looking to replace a Pentax 16-45, preferably with something that goes a little bit longer and is a bit sharper at the edges (my copy is pretty soft at the edges at 16mm) so my shortlist (probably used) is:
Pentax 17-70 SDM – possibly the current favourite and what I would probably have bought instead of the 16-45 if I could have afforded it at the time. Some posts/reviews suggest it may be a bit soft, whilst others call it a “hidden gem”.
Sigma 17-70/f2.8-4 – I've read similar things about this one, seems similar in quality to the above. But I think there may be two versions?
Pentax 18-135 – poor reviews, but real world users seem to like it a lot. And weather sealed. I do have concerns about the edges, would it really be any better than the 16-45?
Tamron 17-50/f2.8 – not really any gain at the long end, but reputedly very sharp. There’s also the Sigma version. The extra stop over an f4 zoom isn’t that important to me but another possibility.
Pentax 16-85 – possibly outclasses the lot, but may be a stretch of budget.
I may be over thinking this, but I tend to prefer buying once and getting it right if that makes sense (had the 16-45 for 7 years mainly used on a K10d) . I currently have a K5iis, and I suppose this may become a K3 (or something else with a higher pixel count) at some point in the future.....
Thanks in advance for any thoughts/suggestions, much appreciated!