[jrpower10]

For wide angle, f4 is probably fast enough in most cases. You'll be able to get away with longer shutter speeds with wide lenses. I use the DA 12-24 indoors as well as the Sigma 8-16. Both work fine with an iso bump.

[Yos]

Your kit lens will cover more than 95% of all situations in terms of focal lengths. Unless you have some very specific needs, a telephoto will have a very limited use and it will be just weight. You can always crop a bit an image to get that telephoto framing; it is not the same, but very close. Ultra wide angles may be useful in some cases but you can always take 2 or 3 overlapping frames at a moderate wide angle (e.g. 24mm portrait orientation) and stitch them together. The results will be of much better quality image and it will have additional resolution.

Some questions to ask yourself are:
Are you willing to always have a bag with you and keep changing lenses all the time?
Is this a photo trip primarily or a regular tourist trip?
Do you have specific plans to photograph certain locations/objects that require special considerations (e.g. low light interior scenes, macro work, architectural details, fill-in flash, etc.)?

Unless you are a street photographer with a particular style that a single prime lens can provide, having a zoom is much more practical. And if you can live with just one zoom for most outings, it will dramatically improve the enjoyment of the visit.

If you are inclined to replace the kit lens anyway, something in the 17-70 or 18-135 will be ideal as a single lens, do-everything.

+1 on that.
The new Sigma sounds like it will cover 95% of your need and then you only need to bring that lens with you.
Sigma 17-70mm F2.8-4 Contemporary Review - Reviews - PentaxForums.com
I would only invest in a super wide angle if you like/plan to take a lot of landscape/architectural photos in the future.
When in a city I usually don't need a telezoom but I do recommend the DA 55-300mm as your telezoom lens.

My two cents

Cheers
Yos

[JimJohnson]

I moved from the K-r to the K-30. To stay within my budget, I sold both the 18-55 and 50-200 kit lenses and purchased the 18-135 with my K-30 .... It was a great decision.

I have been through much of Germany, the length of the Mediterranean and Paris, so I have some idea of what you might be shooting. If I were going back right now and travelling light, I would do exactly what I did in Chicago last weekend - take my DA 18-135 and my DA L 55-300. If I could only take one lens, it would be the 18-135.

To be honest, if you want great architecture photos, you have to shoot with the camera level - not only roll (anti clockwise / clockwise), but also yaw (nose up and down). You will get perspective distortion when either is out of level, and the wider the lens, the greater the perspective distortion. Take a look at my photo at the Chicago River:
https://www.pentaxforums.com/forums/pentax-k-30/192015-post-your-k-30-photos-...ml#post2478438
That's an 18mm shot. The only thing that would have helped was a really, really, really tall ladder. Even an 8mm rectilinear lens wouldn't have done the job without elevation. And I had much more room than I would have had in several European locations.

So... My advice, take it or leave it, is to take your 18-55 and your 40. I think your 40 will get the most use, especially inside buildings with its wider aperture. And rent a DA (or DA L) 55-300 - if that isn't possible, purchase it. Spend some of your savings on good food or other memories. If I have any misgiving about this advice, it is the lack of overlap between the 18-55 and 55-300. It may result in a few more lens changes than you would have with more overlap on focal length.

[ajuett]

We did a road trip in the Canadian Rockies in 2008 and a similar trip for 2 weeks last month. The first time around I had a DA 14mm f/2.8 with me which pretty much stayed glued to the K200D at the time. This time I was on another system/brand and the widest I had was 18mm. We have never been to Europe however, seeing the narrow streets in other people's photos I'd go as wide as possible.

[JimJohnson]

We did a road trip in the Canadian Rockies in 2008 and a similar trip for 2 weeks last month. The first time around I had a DA 14mm f/2.8 with me which pretty much stayed glued to the K200D at the time. This time I was on another system/brand and the widest I had was 18mm. We have never been to Europe however, seeing the narrow streets in other people's photos I'd go as wide as possible.

Or use a longer lens to narrow your field of view so you can focus on your subject without being overwhelmed by the walls or having to be in your subject's face....

My point is that you can make any lens work, it depends more on how the photographer wants the scene to be viewed in his/her images. When I ran the exif tool (Wega) to see what focal lengths I use most often, I see that most of my shots were in a range best defined as 'a short way to either side of normal'. I used wide and long too, but not as often. Somebody else would likely have a different experience. For what it is worth, I've been to both the Rockies and those narrow streets in Europe.

[jeallen01]

The distilled experience of travelling around Western Europe and Egypt over the last 10-15 yrs has now lead me to taking the Pentax 18-135 & Sigma 10-20mm F4/F5.6

The latter lens to be my walk-around lens on the GX-10 & K-5, but the Pentax lens has now taken that role on the K-5 or K-R for the last couple of holidays.

However, the Sigma is still in the bag because it is so useful inside buildings and outdoors in narrow streets and in front of tall buildings!

BTW:
- did consider one of the wider angle lens before buying the Sigma, but I like to keep a filter on the front and you can't do that with the wider ones;
- I have a 55-300 and I take that as well when I am going somewhere that I think I might need it, but that actually very rarely happens .

Overall conclusion - go WIDE!