[robgski]

Pentax 18-135: Versatile zoom range. Weather resistant, fairly compact lens.

DA 18-135 : Great range and fantastic handling. Much more useful than people understand from test charts.

A used 18-135 is your best economical option.

As always, 2 considerations for combining travel and photography are "What kind of traveler am I?" and "What is my preferred of photographic style?" Some people want to see 12 countries in 10 days, and are always on the move, for them, I recommend a good zoom. Others are happy to walk around a few places in one city, maybe revisit the same places at different times of day, and are able to stop, sit, change lenses, wait for the light to be just right, etc. For them, they might want a few primes, they'd rather get one perfect shot and are willing to do what it takes to get that shot.

If you want a durable, lightweight "walk-around" lens with great IQ at an affordable price, the DA 18-135 WR is the best choice.
I travel often, and I prioritize gear that is Lightweight, compact, durable, and reliable. I I have travelled for up to 6 months at a time with only that lens, and a DA 40mm XS prime, and I seldom wished I had anything other lenses with me.

IMO, on APS-C, if you have a lens that closely matches the FOV of the human eye, (including peripheral vision), and are willing to take the time to compose the shot, you will be pleased with your images. For myself, I prefer to take pictures that show why I found a place interesting or breathtaking, not just a shot that shows I stood in the same spot as everyone else does when they capture a well-known landmark I look forward to seeing your pictures.

[wstruth]

The 20-40 is my go to travel lens, albeit too expensive for you now. My current travel kit is the 20-40 and 50-135 (for cost you can go with the 18-135: a nice lens with great range and it's wr) I then supplement it with one or two other lenses depending on where I go and what I feel like. The DA 15mm Limited is always a contender for wide shots and being small, light and having great IQ. The 10-17 fisheye zoom is always a favorite because it's just fun and can be de-fished. There are others, but these are the ones I've used most often because something wider than the standard zoom is always good for interiors and small streets. Personally I do not find a long zoom useful in European cites unless you want to shoot portraits of gargoyles heads (been there done that have have asked myself why I did that). You could probably skip a zoom up to 135 for that matter as well, unless you're travelling outside of cites with time to stop for photos. I used to take a travel zoom (one of those ones with a 60 times zoom) and now leave that home because there is not much use for it.

Lastly the Sigma 17-50 f2.8 is currently on sale New for under $400. I have one, and love the image quality. If I thought I was going to be doing more low light shots, I would take it instead of the 20-40. If I didn't have the 20-40 I would definitely take the Sigma.

[mikesbike]

For a great all around fast pro-style lens, can't beat the Sigma 17-50mm f/2.8 constant aperture lens. Fine build quality, and fast, quiet, accurate AF. Exceptionally low field curvature, even among the best of such lenses. Its imaging is excellent and the f/2.8 is good for low light. However, it is not especially compact, and does not have WR.

The DA 20-40mm f/2.8-4 Limited is a great compact all around lens. Very sharp results. Extremely fine build quality with WR, great imaging, but does have some field curvature that can occasionally show differences in focus in certain instances. Its very compact design is ideal on the KP.

The DA 18-135mm is a wonderful lens. Very versatile and very compact for having such a zoom range. Very well built with WR. Exceptionally fast, accurate, quiet AF. Far better than the older 18-55mm kit lens. Its central-area sharpness is exceptional throughout, and when used between 18-50mm, a good range for landscape use, very good performance even edge to edge. Even up to 70mm for this. Just stop it down a click or so to f/5.6 for better results to get the best edge performance through this range. Its compactness makes it a good combo with the KP.

I have all three of these lenses, and use all of them, which one depending on the situation.

You can always shoot JPEG + RAW to see how your own processing compares with the camera's. The KP's processor is exceptionally good for right out of the camera JPEGs. Don't use the green auto mode unless handing the camera to someone else not acquainted with DSLR use. Shoot in "P" mode if wanting fully automated exposure by the camera, as in this mode you have access to all controls and adjustments. Be sure to set "Fine Sharpening" in the Custom Image menus for superior fine detail in your images, at least in the "Bright" category, which is best for most shooting needs.

[AstroDave]

Let me add my vote for both the Sigma 17-50 and the DA 18-135. These are the two lenses that live on my K-3 (only one at a time!).

[Biro]

I have the DA 20-40mm Limited and enjoy it very much. I think it's a must for the KP. But if the OP is going to spend much time in inner cities on his vacation, I don't think 20mm (30mm full-frame equivalent) will be nearly wide enough. So I'm with those who think the the DA 15mm Limited is a better choice.

Another lens that hasn't been mentioned is the Tamron 10-24mm, which is still available in K mount. But maybe the best deal of all is the Sigma 10-20mm, which has an f/3.5 constant aperture and costs even less than the Tamron. At B&H here in the U.S., it's available for $399 brand new.

[caliscouser]

If it is a fairly limited budget then the 18-135 WR is probably going to be the most versatile travel/walkaround option. Perhaps supplemented by your DA35/2.4 if you need a bit more speed.

A couple of other options that haven't been mentioned. The Sigma 17-70 f/2.8-4, haven't owned it but I like the images I've seen from it. And the Sigma 30 f/1.4, probably the most affordable fast normal lenses around.

[officiousbystander]

Is there no love for the DA 21mm around here any more? It's not fast but it won't matter so much with the KP. It's very affordable 2nd hand. And great for narrow lanes, architecture, and general street photography. And if you're a prime person you may never be satisfied with a cheaper zoom.

[Sandy Hancock]

I'll say it again. In European cities, you're going to want WIDE. 18mm will be quite limiting. I agree that the 18-135 would be a better walk-around zoom than your 18-55, but it doesn't solve the main problem.

The 55-300 variants are great; I'll be taking my PLM to Europe soon, but that's because I'm going to the Le Mans 24-hour race. I probably won't be carrying it around London or Paris.

[Sandy Hancock]

Is there no love for the DA 21mm around here any more?

There's LOTS of love for the DA21. But I reckon the OP would be better served by buying something that isn't already covered by existing lenses.

The 21 goes to Europe:

[normhead]

I quite like the 21 and carry it everywhere, but it doesn't give you the versatility of a zoom, and for my landscape kit these days, it's not full frame. I could really use a 21 on my K_1. It's sad.

[grispie]

have upgraded to the KP. I am due to go on holiday soon to Europe. Considering to upgrade lenses but to an economical option, compact with the best AF, maybe just one walk about.

I understand you are looking for an improvement over the 18 55 wr but with a budget constraint.
Personally i can appreciate the 18 55 wr. You can take good solid shots with it. This said: in good light at optimal settings...

When looking at replacing the 18 55 (thus a walk about) i'd be looking at two options, both economical 2nd hand:
pentax da16 45 or da 17 70. I owned both. The 17 70 being more versatile because of the longer reach.
IQ wise, they are both very fine lenses, a true step beyond the 18 55. Do not expect really compact or fast AF..

If you're interested, you can find shots with da16 45 in my US gallery (smugmug below..) and some samples 17 70 in mexico and france gallery.

As others mentioned, there are a lot of options. Maybe tamron 17 50 2.8 is one of them.

Also mentioned by others: da 15. I also have it and really like it. Especially would be very nice in european cities. Da21 for a bit more conventional focal length. I do have the feeling you are looking more for a quality standard zoom in addition to your two primes.

16 85 would seem the best for you, but not sure whether this is within your budget. I don't own that lens, since i really like my da 17 70...

comes down to this i guess:

All in all I'd say there's no clear recommendation to make here gear-wise, other than to look at all the suggestions and compare them and to penultimately decide for himself what is more important.

best of luck

[robgski]

FWIW, a PF member is offering an M42 mount 17mm FE lens for an incredibly low price. I own one, and on APS-C, it is a very wide-angle lens with minimal FE . This lens was the second prime I purchased, and it stays on my camera for weeks at a time.

[MrB1]

I have upgraded to the KP. I am due to go on holiday soon to Europe. Considering to upgrade lenses but to an economical option, compact with the best AF, maybe just one walk about.

To fulfil that brief it is doubtful that there would be anything else that could compare with the DA 18-135.

e.g. used-pentax-da-18-135mm

[Saltwater Images]

You already have a 35 & a 50. As others have stated the 15 will round out your current kit nicely. I have been shooting with HD DA Limited’s since 2015. Depending on travel destination my compact travel setup is either HD DA 21/40/70 or HD DA 15/35/70. Given that you have a 35mm lens the 15 is the logical choice. I started shooting Limited’s on a K-5II and recently upgraded to a KP. The KP with a Limited lens is pure joy to shoot with.

[Sandy Hancock]

The KP with a Limited lens is pure joy to shoot with.

He speaks the truth.