I think that Tamron lens would be fine for hiking if it's not too heavy, and if you think you may want to go full-frame at some point in the future, probably a good investment. However for your immediate goals, I'd suggest this:
HD Pentax-DA 16-85mm F3.5-5.6 ED DC WR Reviews - DA Zoom Lenses - Pentax Lens Reviews & Lens Database
Pentax HD PENTAX DA 16-85mm f/3.5-5.6 ED DC WR Lens 21387 B&H

[ToddK]

In case the DA18-135 interests you, there is a refurbished one on the Ricoh website for $299 USD.

[stemked]

If you want to get a couple of nice, inexpensive, light-weight lenses there is nothing wrong with Pentax's 18-55 WR +55-200mm. They are inexpensive lenses and you can get both for about $180. You can subsitute the longer lens with the 55-300 (there are three versions of this lens, all great 1st cheapest, no Water Resistance, 2nd with WR, 3rd most expensive but the sharpest). The nice thing is if you are getting started you can start with these lenses, have a lot of fun, they are VERY light weight, and you can purchase more expensive lenses if and when you feel the need to up your game.

[ramseybuckeye]

Yes, I should have mentioned what I have.
Currently, I have two lenses that came with my Ist D.
DA 18-55 1:3.5-5.6 Pentax
SMC Pentax - FAJ 75-300 1:4.5-5.8

And I also have a Sigma 170-500 1:5-6.3 APO DG

I'm really looking for a decent lens that can me the only lens I carry for most of my hikes. Generally speaking it will be for small birds / animals in the 30' - 300' range with some landscape tossed in.
My inexperienced thought was that with the lower light conditions, (wooded cloudy), I would want to satay at the lower aperture number ?

My advice.
Use some proper photo software.
Do some hiking walkind with photography of what you have.
Analyse photos and see the most of the focus range you are using vs the most satisfying results.
Think how often something was too close or out of reach. Then come back and ask - usually when you analyse your ranges you will be pretty sure what you need.

Put some significant investment in lens that will be good enough to stay with you until the end of your adventure with Pentax.

Good advise. Using what you have is the best way to find what you need. I started with the HD 16-85 and now walk around with the HD DA 15mm F4 ED AL Limited and the HD DA 35mm F2.8 Limited Macro. The zoom is great, and but the primes make me think a bit more before I shoot.

I agree with this, and the reason is that the K-70 is going to blow the Ist D out of the water, lower light shooting is going to change a lot. I have a KP which is similar to the K-70 in lower light. I previously shot with K-50, K-30, and K20D. each new model has some improvements, but the jump to the KP from the K-50 was astounding in lower light shooting. I've lived in North Carolina for 8 months and the woods is different in the area I'm at with longleaf pines that let a lot of light through the canopy. Previously in Ohio, I know the low light that you can get in the woods. What worked best for me?

DA 55-300 PLM F4.5-6.3, not fast but very usable wide open, good IQ, and the fastest autofocus on any Pentax lens, and it's weather sealed. If will give you a lot more usability than your FAJ lens. I feel the 55-300 PLM is the most versatile lens in the Pentax lineup, at least for the cost, definitely most bang for the buck lens. If you only want to carry one lens in the woods, that's the one.

DA 300* F4, obviously more expensive and less flexible, but a superior lens that is relatively fast at F4, and smaller than your Sigma, and weather sealed. But if you like the Sigma there is nothing wrong with it.

A macro lens is another that I likes to carry for closeup in the woods, I would not get that yet unless you see a great deal on one.

For wider there are a lot of ways, you could use your kit, or go with a small prime like the 15 or 21, or I highly recommend the DA 20-40 Ltd, since it is fast ,small, and weather sealed. Sometimes I'll go on a hike with just the 55-300 or 300*, or more often I have a small sling with me and also include the DA20=40, DA 15, and possibly a 50 or 90 macro, which are also small lenses. I've recently added the DA 1.4 converter which adds very little size and weight.

But again, try your lenses out on the new camera first. The biggest upgrade would be the 55-300 PLM.

[UncleVanya]

I’m out of shape and not hiking much these days, and when I hiked it was mostly short hikes (no overnight hikes). I personally lean towards a bridge camera or other smaller sensor cameras for this reason, but in the past I carried the 18-135 and 55-300 or 18-55 50-200 combo.

[jgnfld]

My typical hiking/sailing kit is DA16-85, 55-300 PLM, DFA 100 macro, plus usually the 40 Ltd is in a side pants pocket in a pouch for golden hour (which it renders beautifully). Especially around now since golden hour is so long at this latitude and season as the Sun never gets higher than 19o.

My suggestion is you will not be disappointed on the trail by the first two for most purposes you run across hiking on the trail. If you are stalking some special assignment you might want other lens gear. On an out-and-back trip I often switch general zooms at the turnaround point--especially if good wider angle landscapes present themselves.

On the trail (or in my case trail or boat) Pentax general zooms are much preferred (by me) over Tamron/Sigma as they are weather sealed, and where I live, at least, this is a REAL issue. As well, I find my Sigmas (10-20 and 17-50) both tend to fail at or before -10C (14F) while my Pentax lenses generally go to around -17C (~0F) which is as cold as it generally gets here. Michigan is colder than Newfoundland, of course. But we have extremely windy and very often WET cold which really is different (I've lived in northern Minn down to -51F and been warmer). NO one wears goose down outers here, for example...it's worthless except as an inner layer like a vest.

Words of caution: You still do need to be careful about zooming with a wet barrel on zoom lenses even with Pentax weather sealing due to suction.

[macman24054]

I have this lens and it is a great lens but maybe not so much for your use. I'd say the 55-300 is your best choice.

[Apet-Sure]

Welcome to the forum! Nice to have you with us. Getting a new K-70, huh? You Lucky Dog!

I'll second what ramseybuckeye said about the low light capability of the KP / K-70 cameras. (He really should call himself ramseytarheel now that he lives in North Carolina. ) With my K-10D I kept the ISO at 400 or below for good IQ. With my K-5IIs it was 1600 or below. With my KP it's 6400 or 8000. But I've seen an image a member posted shot at 10,000 supposedly with little noise reduction in post processing, and it was amazingly good.

Both the Pentax 18-135mm and 55-300mm PLM lenses are much discussed and highly regarded here on PF. For wildlife, 300mm will be useful. Anything much shorter and you'll need very tame, human-acclimatized wildlife. I've shot squirrels 30 feet away with my DA* 60-250mm with good results. The birds at my feeder seem to know that I'm the guy who loads it with suet. Some of them let me get within 10 feet and shoot with my Pentax-F 100mm f/2.8 Macro.

If I could afford a Pentax DA 16-85mm I'd get one. My K-10D came with a Pentax 18-55mm. I soon replaced it with a Sigma 17-70mm DC Macro; big improvement in IQ. The 16-85 would be an incremental improvement again in IQ, though slower, but I can't justify the cost. It seems that the 16-85mm range would be perfect for a general purpose walk-around lens.

For bugs and flowers you'll eventually want a Macro (1:1) lens. I can highly recommend the Pentax-F 100mm f/2.8 Macro or its later cousins.

[UncleVanya]

For hiking macro I’d typically suggest the Raynox add on lenses, but the base lens matters. Since you are working on deciding what you will carry I’d want to know that before committing to the suggestion.

[Des]

Welcome to PF. You will love the K-70 and be amazed at how capable it is.

You've had lots of good advice already, so I'll just add some comments from my own experience. (Nature photography is my main area of interest too.)

My hiking kit varies. For one lens, it's either the DA 18-135 or 55-300 PLM, depending on what I expect to come across. My two-lens kit was generally 55-300 with either the DA 12-24 or DA 18-135. Nowadays I mostly take the DA 15 Limited, DA 20-40 Limited and DA 55-300 - high quality, compact and light weight. Sometimes it's just the 20-40 and 55-300 (both WR), but the 15 is so pocketable and such a joy to use that it's hard to leave behind even if I don't use it so often. But the trade-off here is more lens-changes. For simplicity, I would suggest the 55-300 PLM with either the 16-85 (if within budget) or the 18-135.

Like others here, I would often add a macro to the kit (FA 50 f2.8 or DFA 100 f2.8 WR) or take it in place of one of the others. They are crazy sharp, great not only for true macro but also flowers, leaves, fungi, butterflies if reasonably close, any detail of interest and f2.8 is handy for subject separation. I also find a macro lens to be a great base for stitching images together, like this.

(Stitched with Microsoft Image Composite Editor, which is free and easy to use - Microsoft Image Composite Editor) A tripod is best for this, but if you are careful you can do it with handheld images.

I'm really looking for a decent lens that can me the only lens I carry for most of my hikes. Generally speaking it will be for small birds / animals in the 30' - 300' range with some landscape tossed in.

If it's a big animal, the 55-300 PLM would be OK for 30-60 feet.




But for small to medium birds and animals, I'd echo the point Norm and others have made: beyond 30 feet, with a 300mm lens the subject is often going to be too small in the frame to give more than a record of what you saw.

And I also have a Sigma 170-500 1:5-6.3 APO DG

I used to have one of these (non-DG version). Mine was fun but not very sharp at the long end. (And a beast to carry, even though it is lighter than other 500mm lenses.) However others seem to have got better results with it. See the reviews here:
Sigma 170-500mm F5-6.3 APO Lens Reviews - Sigma Lenses - Pentax Lens Review Database
Sigma 170-500mm F5-6.3 APO DG Lens Reviews - Sigma Lenses - Pentax Lens Review Database
For wildlife at a distance, you do really need upwards of 400mm and your existing lens is as good a place to start as any. It will be a different experience on the K-70 than on the *ist - e.g. far better autofocus, better burst speed, far better low light/high ISO performance, to mention just a few things. There are very few 500mm autofocus options in Pentax and anything else is going to be heavier and more expensive, so give this a serious try.

[rr1736]

The SIgma 18-250 is a good walking around lens

[shyrsio]

If you're tight on budget you should get a second hand Da 17-70/4, its very cheap nowadays, and it has a stellar performance in comparison to the kit lens. otherwise if cou can afford it, get the 16-85. That lens is arguably the best APSC performer from Pentax.

[Michail_P]

My advice.
Use some proper photo software.
Do some hiking walkind with photography of what you have.
Analyse photos and see the most of the focus range you are using vs the most satisfying results.
Think how often something was too close or out of reach. Then come back and ask - usually when you analyse your ranges you will be pretty sure what you need.

Put some significant investment in lens that will be good enough to stay with you untill the end of your adventure with Pentax.

Couldn’t get better advice. The lenses you already have can cover a very long range of subjects. Take your time, buy the lens you will certainly use a lot. Hiking should be light. I really can’t imagine how some fellas do it with so much gear.

[UncleVanya]

Truth be told most of the time these days on the short hikes I still take I am carrying m43 gear. But there are times when I prefer to take the K-3 and the 18-135 is my most often taken lens at that point. The 18-50 sometimes gets the nod but that isn’t typical.

[robgski]

DA 18-135mm WR. Lightweight, good enough to great results at all focal lengths. It was my only travel kit for 6 months and I rarely wanted anything else. Here are a few hundred reasons why.