The cost is likely to be low, so the risk equally so, perhaps try something and see? If you stick to recognisable makes, even ideally finding a Pentax branded set, then it should reasonable. You're quite right to want to avoid anything cheap and nasty that might damage the finish on your camera mount.

If it helps I have an Asahi Bellows Unit here, M42 fittings, in original box with instruction manual and virtually unused. £25 including shipping?

There must be thousands of sets of M42 extension tubes available. I probably have some somewhere as well. Try M42, 42mm, Pentax, Pentax S and Praktica as searches.

You'll need Pentax K mount tubes for the bayonet lenses. Pentax made a beautifully engineered set and there were plenty of others. A set of these tubes plus a Mount Adapter K would enable you to use the screw thread lenses on them.

In times of yore cameras were updated in terms of facilities, such as TTL metering, AF, built in motors, etc. To an extent lenses also developed with zooms becoming possible and wider aperture primes. But the core quality of the film after the 1970s was pretty much the same. If we wanted to use Kodak Technical Pan film (ISO 16) for the ultimate in resolution then we could. Did we? Probably not.

What's different now is that whereas said Kodak film could be put in any camera to reap its benefits (providing we are talking about SLR lens quality) whereas now not every DSLR or CSC will produce the same quality. If we spend more, if we upgrade, then we can get better images technically. Changing an MX for an LX would not have affected quality in the slightest. Changing an *istDS for a K-3 II certainly will.

What's also different is that virtually nobody used the finest grain, sharpest films, but far more want to shoot RAW and ISO 100 in the belief that it will be the minimum requirement for good images. What camera we use can change the way we shoot images.

The 24-90mm was a premium quality standard zoom. We used one on the MZ-3. It's actually a great lens. The only reason I sold ours was that on APS-C having the 12-24mm and the 24-90mm didn't work out as being convenient. So many shots were around 24mm I was forever changing lenses.

I wish I had one now as it would be useful again on the K-1.

This is always tricky as the real question will be will the lens suit you. The only way to be sure is to try it, although reviews can be your guide.

As a generality, I'd prefer less zoom range as the quality is probably better and the aperture at the long end perhaps more realistic. Also consider weather resistance and how important that will be to you. Also, how close would you like a lens to focus?

Pentax make an 18-270mm that will be on offer at the moment, and that could be an excellent travel zoom. Certainly its predecessor, the 18-250mm, is a versatile and good quality lens. No weather resistance though.

Perhaps search the web to see how the 18-300mm has been received generally?

Lensbaby lenses are fantastic to play with, its the letting go and seeing things in a freer way that I found the difficult bit. I had a Lensbaby Twist 60 in for review and enjoyed using that, but it's different from yours in that the lens didn't bend. They make us think in a new way that puts less emphasis on technical quality, that's for sure.

I've moved this to Leads to Deals, but I expect Chris will be advising any deals directly in due course.

I think there's a difference between being caught in a rain shower and being immersed in a body of water. In the first instance we would remain relatively dry apart from our coat and hat, in the second instance we would be saturated from head to foot.

In a similar way, weather resistance is one thing and I have been out with my K-5 and K-1 in torrential downpours with no problem. I wouldn't immerse one in a bucket of water or a lake though. I see a distinct difference between these two scenarios.

The K-1 is definitely not marketed as waterproof. The WG series are waterproof cameras and they can be submerged down to specified depths for specified times.

The DSLRs are weather resistant. They can resist rain, sleet, snow, etc. and also low temperatures to -10C. But resistant is not weather proof, nor is it waterproof. Some other manufacturers describe it as moisture and dust resistant, able to resist splashes.

Just use "Save As" instead of "Save for Web", after you have resized of course.