[Sandy Hancock]

Pentax F 28/2.8 - this is a superb, tiny lens. Definitely a keeper for the K-1.

Pentax DA 50/1.8 or Pentax FA 50/1.4 - I'd lean towards the FA for the extra half stop and the aperture ring, but in reality, why not just test them side by side when you get the new camera?

Pentax F 35-70/3.5-3.5 'macro' - I have no experience with it, but all reports are positive.

As already mentioned, I'd look seriously at the DFA28-105. You don't have a weather sealed full frame lens, and it is relatively cheap, quite compact and extremely versatile, with modern coatings and focus motor.

If you want a longer option, I'm a big fan of the DFA70-210. It's much lighter than the f/2.8 options, and it handles beautifully with internal focus and zoom. The 55-300 variants are not particularly full frame compatible, so you'd be spending a lot of time cropping to deal with soft corners and/or vignetting, as well as sacrificing over stop of light.

If you want a cheaper telephoto option with all (well most) of the modern trimmings, consider a second hand DA*200. The IQ is superb, it is smaller and lighter than many of the zooms, it's absolutely full frame compatible, and is AW sealed.

When all is said and done though, you have a pretty good starter kit already. Get the camera and figure about what you really need later. In the meantime you can always use crop mode

[aslyfox]

Yep, I'd need something around 85mm but it can wait a bit.

when you get around to that, is 100mm too long?

there is the Pentax 100mm F2.8 Macro " family " that you might consider:

Pentax-D FA 100mm F2.8 WR Macro Review
Introduction
The SMC Pentax-D FA Macro 100mm F2.8 WR is a fixed focal length macro lens which can focus down to life-size magnification (1:1), and which doubles as a versatile short-telephoto lens. It features a weather-sealed metal lens barrel and top-notch optical quality in a small and light package, and as such is designed much like a DA Limited series lens. . . .

Pentax-D FA 100mm F2.8 WR Macro Review
Specifications
The lens covers the full 24x36mm format, not just APS-C. The aperture blades are rounded, delivering a smoother bokeh which is important for a macro lens. However, unlike its predecessor, it has no aperture ring.


The optical design is the tried-and-proven formula of the previous generation D FA 100mm F2.8 Macro lens, which in turn had inherited the optical design from the well-respected FA 100mm F2.8 and F 100mm F2.8 macro lenses introduced in 1991 and 1987, respectively. None of these earlier lenses had rounded aperture blades. . . .

Read more at: Pentax-D FA 100mm F2.8 WR Macro Review - Specifications | PentaxForums.com Reviews

[MarkJerling]

The F35-70 f/3.5-4.5 is a super little lens and should be a very serviceable walk-around zoom for the K-1. I bought mine after seeing the results @MarkJerling got with his, and whilst I use mine on APS-C (as Mark did originally), I believe he now uses his on the K-1II with good results. I've read positive feedback from others who use theirs on full frame, too. 35 - 70mm on full frame is a pretty versatile range - more so than with APS-C, for general shooting. Paired with your F28 f/2.8, you'd be well set to begin with...

Mike's right, of course! Several people here refer to the F35-70 as "a bunch of primes". I think that's a very apt description.

[Nuftur]

The change from K-5 to K-1 is a full system change, because you cannot use your APS lenses anymore (except the APS mode of the K-1 which makes it a 15MP APS camera).
For that, you better stay with a new APS body or you have to invest heavily, as you won't get much for the old stuff.

BR Nuftur

[mikeprotts]

The change from K-5 to K-1 is a full system change, because you cannot use your APS lenses anymore (except the APS mode of the K-1 which makes it a 15MP APS camera).
For that, you better stay with a new APS body or you have to invest heavily, as you won't get much for the old stuff.

BR Nuftur

Most DA lenses provide a much larger area than the crop mode, and are also worthwhile as a stop gap when upgrading to FF.

[ecostigny]

Some DA lenses provide decent coverage, but many do not: Full Frame Coverage of DA Lenses: Comprehensive Test - Gear Guides | PentaxForums.com

[mikeprotts]

Some DA lenses provide decent coverage, but many do not: Full Frame Coverage of DA Lenses: Comprehensive Test - Gear Guides | PentaxForums.com

My post from the 15th in this thread has an example of the difference between APS-C, usable area and FF, and attached a pdf with the approximate coverage for the lenses I have. It may not be ideal to use a DA lens, but they are useful while migrating to FF.

[ecostigny]

My post from the 15th in this thread has an example of the difference between APS-C, usable area and FF, and attached a pdf with the approximate coverage for the lenses I have. It may not be ideal to use a DA lens, but they are useful while migrating to FF.

I missed that one somehow, including the link I needlessly duplicated in my post. Seems to me that the migration process would involve determining what acceptable coverage you have with your existing lenses and then filling the gaps with new purchases (as your budget allows).

For example, if I were to go to FF, I do have a Sigma "digital ready" 24-60mm f2.8 autofocus zoom lens that could sustain me for a while (I bought it originally for my MZ-S). Since my DA 55-300 f4-5.8 zoom is only potentially useful for FF when stopped way down, my next logical investment might be the DA* 60-250mm or the DA* 300mm.

I also have some 1980s K-mount lenses as well (all manual focus). That's one advantage of jumping into the Pentax system years before they began their digital offerings exclusively with cropped sensors.

[MarkJerling]

The change from K-5 to K-1 is a full system change, because you cannot use your APS lenses anymore (except the APS mode of the K-1 which makes it a 15MP APS camera).
For that, you better stay with a new APS body or you have to invest heavily, as you won't get much for the old stuff.

BR Nuftur

Almost every lens I used on my K5 still works very well on the K-1. Even the (few) lenses that need crop mode to not vignette badly.

[thibs]

Seems my K1 should arrive soon if all goes well.
Thanks again to everybody

[Lowell Goudge]

An updated APS is a possibility too. The thing is, apart the WANT thing I have a lot of older manual lenses which I'd really like to use as they were (specially my K30/2.8) so I'm considering going FF. Not sure though, which is why I asked for your help

The problem with my K5 is AF. Tracking for sure but besides AF inside in relatively dim light: slow and imprecise (IMO).

Although a newer body will have better AF, I have never found the low light and af tracking of my K5 an issue. I think all cameras of that era have issues, not just Pentax. I think there needs to be some view of what is practical, in terms of AF performance, it may be your expectations are unreasonable. I don’t know, and this is just a question because having shot with Pentax AF since the film era and the PZ1, what cameras do now is exceptional. Can they be better, perhaps yes, but......

[thibs]

Although a newer body will have better AF, I have never found the low light and af tracking of my K5 an issue. I think all cameras of that era have issues, not just Pentax. I think there needs to be some view of what is practical, in terms of AF performance, it may be your expectations are unreasonable. I don’t know, and this is just a question because having shot with Pentax AF since the film era and the PZ1, what cameras do now is exceptional. Can they be better, perhaps yes, but......

It is mainly indoor/tungsten lights being the most problematic. The K5 (not II), at least mind really struggles there and either a slow zoom or a "not that sharp with long focus throw" as the FA50/1.4 is a problem.
The K-1 is quite snappier. Not that it is revolutionary or anything but is enough to track a not so fast (for now) kid so I'm happy.

Sometimes I feel like the old very narrow 1 point-only Z1 AF was a heck of a lot snappier than anything from MZ-5 to K5. It probably is just perception though.
I'll try to grab a not too expensive 2CR5 and use my Z1 again to check.

[Lowell Goudge]

It is mainly indoor/tungsten lights being the most problematic. The K5 (not II), at least mind really struggles there and either a slow zoom or a "not that sharp with long focus throw" as the FA50/1.4 is a problem.
The K-1 is quite snappier. Not that it is revolutionary or anything but is enough to track a not so fast (for now) kid so I'm happy.

clear

Sometimes I feel like the old very narrow 1 point-only Z1 AF was a heck of a lot snappier than anything from MZ-5 to K5. It probably is just perception though.
I'll try to grab a not too expensive 2CR5 and use my Z1 again to check.

in some ways i agree with you. the only time i really screwed up the PZ-1 was when i put my daughter on a swing, sinusoidal motion was definitely NOT what the designers had in mind with predictive autofocus

[thibs]

clear in some ways i agree with you. the only time i really screwed up the PZ-1 was when i put my daughter on a swing, sinusoidal motion was definitely NOT what the designers had in mind with predictive autofocus

LOL yes, I think I get what you mean.
My daughter decided this weekend that life was boring down there so she figured walking on both feet was funnier. Fortunately I got the K-1 just in time.

[Lowell Goudge]

LOL yes, I think I get what you mean.
My daughter decided this weekend that life was boring down there so she figured walking on both feet was funnier. Fortunately I got the K-1 just in time.

As a follow on thought, in the early days of DSLRs, there was a huge discussion on focusing errors under tungsten lighting. Might be something worth checking on.