[Just1MoreDave]

Practical vacation use starts to run out around 300mm. The lens is likely f5.6 or slower, and you want a shutter speed that works for handholding. Those numbers mean outdoor daylight shots are OK, but in less light, you're raising ISO, looking for a tripod substitute, going to 200mm, etc. If I had a DA 55-300, I would take it, I just wouldn't expect to use it a lot at 300mm.

[thornburg]

Others have already given you great advice, but I can't help but add my two cents.

I think that if you're traveling light, the 18-135 should be fine on its own. If you're going anywhere where you might want to take pictures of animals, or of people far away from you, bring a zoom telephoto (55-300, 70-300, 100-300, etc).

I just got back from a trip myself. (The Pentaxian in the family is my girlfriend, and although I frequently use her camera, I did not bring it on the trip--it was a business trip, and she was unable to come along.)

What I did have on the trip was another brand DSLR, along with 3 lenses: 24-85 (AF), 200 (MF), 55/1.8 (MF). I chose the MF lenses because they were lighter. It was a mistake. I really wished for my AF 70-300. I had a lesser wish for my AF 50/1.7 for low light.

Given what I learned, here's what I would say is the "ideal" lens kit for traveling:
(replace with appropriate lenses based on your budget -- if your bag is full of Ltd primes and DA* zooms, use those, if you've got an 18-55 kit lens and a 75-300 from yard sale, bring those)

Minimal Kit, single lens
---------------------------
zoom: 18-135 or 18-200

Light Kit, two lenses (landscapes or cities)
---------------------------------
wide angle: 14mm or 15mm prime, or any Wide Zoom (short end shorter than 15mm)
zoom: 18-135 or 18-200


Light Kit, two lenses (wildlife or distant people)
---------------------------
zoom: 18-135 or 18-55
long zoom: 55-300 or 70-300

Large Kit, three lenses
---------------------------
wide angle: 14mm or 15mm prime, or any Wide Zoom (short end shorter than 15mm)
short zoom: 16-50/2.8 or similar (kit lens if you're on a budget)
long zoom: 55-300 or 70-300

Full Kit (any trip)
---------------------------
wide angle: 14mm or 15mm prime, or any Wide Zoom (short end shorter than 15mm)
fast prime: 35/2 or 50/1.8 or 50/1.4 or similar
short zoom: 16-50/2.8 or similar (kit lens if you're on a budget)
long zoom: 55-300 or 70-300


The only way I would switch that up is you expect a lot of indoor/night work, where you need to focus more an apertures and less on focal lengths.

[DeadJohn]

@Newtophotos, I am going to assume you're new to the hobby based on your username. The 18-135 is fine for your first vacation trip with the camera. You get weather resistance and a versatile zoom range.

Other lenses to consider would be something wider (Tamron 10-24, DA15, Samyang 14mm, etc.) for indoor architectural shots, and something longer (the 55-300 is reasonably priced plus compact for traveling lightly) if visiting parks for wildlife. Don't agonize over going on vacation without them, though. Use the 18-135 and add lenses later as you notice gaps in what your current lenses can do.

[Tanzer]

You'll do fine. If you have to ask the question, you haven't established for yourself what your preferred focal length range is. And who are we to tell you what you should do.

Look at it this way, the 18-135 gives you much better zoom range than ye olde 35-70 zoom lenses of yore. So, enjoy the vacation, and take lots of pics!

You can always find a situation where you can kick yourself for not having a wide enough or long enough lens, if you try hard enough. Sometimes I wish I could hover in thin air to get a better perspective, but I just have to make do with where my two feet will carry me.

For the next trip, you might well decide that you want a wider, or longer, lens in your vacation bag. Or maybe not.

[emalvick]

It depends on the location. Last year in Iceland, I used my 10-24 and 17-50 for 99% of my shots. I also had a 55-300 and used it for the other 1%. On a previous trip I only had the 17-50 and 55-300 and used both almost 50% because there was a lot of wildlife. I think that if I had the 18-135 (which I do now), I'd probably be close to not needing the 55-300.

I think 17-18 is going to be wide enough for most people, BUT, location and mean a lot. Indoor shots can benefit from wider. I took a lot of shots in canyons and up close of things that the wide angle worked well for. Stitching is a reasonable solution, but it can get annoying to be taking a lot of shots to compensate because you can't get wide enough to just take 1.

I'm actually going to Yellowstone and Grand Teton NP's in a couple of weeks. I think I will bring the 10-24, 17-50, and 55-300 again. My wife will have the 18-135. Given the location, I suspect the 17-50 will suffice most of the time except maybe the wildlife of which I don't really shoot a ton of anyway. If I didn't like my 17-50 so much, I'd probably try the 18-135 myself, but I find the 17-50 still has an edge in terms of sharpness for me. I suspect the 10-24 will only see use for night shots of the sky. Contrary to the earlier discussion, I don't swap for it unless I see a few shots being needed. Otherwise having a couple of shots to stitch isn't such a nuisance.

[jimr-pdx]

Just remember when things get tight: turn the 18-135 vertical at 18mm and overlap a few shots, for a panorama stitch later. I would find 18mm confining at times in the High Sierra canyons, but my 16-45 will suit me fine for wide shots - and panorama stitching will fix any issues that come up.