Standard zoom options for the K1

I went for the new 28-105mm lens and that's been great.

The Tamron 28-75 F2.8 is reportedly a lot of bang per buck. Available new also. But I'd only go for it over the Pentax 28-105 if you'd find F5.6 at the long end a problem. For most scenarios it's not really ...I get close-ups and portraits from the 28-105 at the long end with beautiful bokeh. Plus the DC focussing and quick shift and build put it in a higher class than the old Tamron. But there's a price difference, although both offer very good value for what they are.

The F35-70, very cheap, will give good IQ so long as you use a hood, and don't point it into the sun too much, but focusing can be frustrating as I find it is often reluctant to lock on.

I'd give Cambrian photography in Colwyn Bay a shout - sometimes they have a good selection of used lenses - prices are reasonable.

I've used the FA*28-70 on mine and had no problems with it at all.... Just a pain when using Lee Filters due to the rotating front element.

I can share my experience using Tokina AT-X 28-70mm-f2.8 with K-1. It is the first version of these Tokinas, the one with light orange marking ring and 72 mm filter thread. I bought it long ago and occasionally used with K100d super as fast zoom. Later, with K5II I almost never used it, as 20-40 was sufficient and more convenient zoom for crop.

Now I too didn’t buy Pentax 24-70mm together with used K-1, mainly due to the size, as price for used lens was rather good.

Tokina AT-X 28-70mm-f2.8 is not optimized for digital but in certain conditions works well.

Advantages:
compact for a 2.8 fast lens;
sharp in 28-45 mm range from the f 2.8;
pleasant bokeh (not with any special character, but without any annoyances).

Distavantages:
in 50-70 mm range sharp only from f 4 (especially 70mm)
suitable only indoors, if outdoors, only in cloudy weather. Bright sky, especially the sky side with the Sun is no-go for the lens, contrast drops significantly;
my item doesn’t focus well to infinity at 28 mm. Infinity focus in 29-30 mm is OK.

Another vote for the Tamron 28-75 f2.8 its a very compact, competitively priced lens. Especially in the second hand market. Very sharp, fast and light.
I now have the Pentax 24-70 on my K1 and I will say, you pay a lot of money for an extra 4mm at the wide end.. And you gain a lot of weight and WR of course... Though I found the 28-75 never quite wide enough for landscapes a fabulous portrait lens.... Only 67mm filter thread which helps !!

Don't discount using a prime as K-1 images can stand serious cropping.
See my squirrel photo here: https://www.pentaxuser.com/forum/topic/garden-visitor-this-afternoon-56410/p-0#c... along with the full uncropped version from which it was made further into that thread.

I have the 28-105 snd 24-70.

I Would buy the 28-105 everytime.

The price of the 24-70 is not justifiable and the size of makes it a real burden.

Optically the smaller lens is not over shadowed by the bigger lens and it is so compact and pocketable; the extral zoom length is a bigger advantage than the slight loss of width at the other end, which in a practicsl sense does not prove to be a significant impediment.

I have tested them side by side on the same subject under identical conditions and the difference is not worth worrying about.

The extra weight and price of the 24-70 makes it a “ never would buy again” lens.

It is a beast for sure

There's a Tamron 24-70 vs 28-75 comparison here which confirms Stub's thoughts. https://www.youtube.com/watch?v=5GN6FRWcb1k

I do have the 24-70; being a bit wider and a little bit sharper towards the edges makes it better for landscape I think. I found the weight of it appalling at first, but when I realised how useful it was I decided it was worthwhile, and got used to it.

What you want is the Pentax new D-FA* Platinum Series 10mm-150mm f2.0 (a prototype I've been testing for them for a year or so now), it has a 49mm non rotating filter ring, weighs 232gm and is 84mm in length and targeted at a RRP of £249. I find it covers most needs - but until it's released you'll have to make do with one of the other suggestions

Consider one of the Sigma 17-70's - they (at least the early versions) are FF-compatible, and my very old (1st gen) version is very sharp on my APS-C K-30 and K-3 / K-3 II. Lots of info on the US Pentaxforums.com website.

They're definitely not FF compatible mainly because that wide end of 17mm is super wide (so there would be significant vignetting). If they were FF compatible I'm sure many people would have snapped one up for the ultra versatile range