I can get away with the dioptre adjustment on my DSLRs but need glasses with compacts and my ME Super (one thing I don't like about using a compact is fishing out my glasses, maybe taking sunglasses off first and finding an empty pocket to put them in - note to myself to buy a compact with a viewfinder next time). I need glasses to make sense of the screen menus on the K20, but for the K5 at a pinch I can do without.

That's assuming that they want to; there's a wide range of price-points in FF DSLRs just as there are with smaller-sensor ones.

For landscape, I'd agree.

When I first learned to use a film SLR the rule of thumb (assuming a 50mm lens) seemed to be f/16 or more to give a decent depth of field; in reality with ISO100 print film, or ISO25 or 64 for slides, that either meant a tripod or compromising with a wider aperture. With the DSLRs I'm usually in the f/9-f/11 range without any problem.

If I've got the technicalities right it's basically because a smaller sensor will use a shorter focal length for the same shot - so say 34mm with a 16x24 sensor v. 50mm with 35mm FF/film.

On the other hand if you want a small DoF e.g. for portraits then a larger sensor makes sense (pardon the pun!).

I already have one, it's called an ME Super!

Joking aside, it wouldn't surprise me if a FF Pentax came out before long, but at the moment it seems that all we are hearing is thinking and speculation. Logically though there is a gap at this point in the Pentax range between the K5 and the 645D (how many people here own, or are considering, a 645D?).

It seems to me that there's something of a convergence of technology going on. Image quality with smaller sensors is improving (24Mp without noise penalties?), giving weight and size advantages for camera and lenses; on the other hand I suspect it won't be long before a 24x36 sensor appears in a body no heavier than the K5's (I think the Nikon D600 isn't far off anyway), though rather longer before the price comes down to the same level.

That's good to know, I had the same problem with my K20D - particularly annoying if it picked up dust when I was away for a week or two without the computer.

My replacement K5IIs is back from SRS now - very quick turnaround, much appreciated. I've just had a wander around Exeter Cathedral and the coast at Beer, Axmouth and Lyme, mix of indoor, overcast and sunny conditions.

Early thoughts (I'm comparing with a K20D, so...)

Much better low-light performance - acceptable at 12800, sharp at 1600
Quicker autofocus (tried with DA17-70 and DA55-300 so far)
Slightly sharper at ISO100/200 - particularly for fine detail (on 24" screen)
Better exposure - fewer images underexposed, seems to show more detail in shadow
Ergonomics slightly better - e.g. I like the ISO button
Marginally brighter viewfinder
Not quite so natural feel in my long hands - though the RH grip gives better confidence for picking up one-handed
Not keen on the rubber cover for the ports
Like the start-up dust removal - doesn't sound like the K20's machine-gun
Exposure compensation in AV mode doesn't clear on turning the camera off - probably a case of getting used to it rather than a problem.

Overall the process of composing and taking a shot seems quicker and 'cleaner' than with the K20, more like (and even slightly better than) the Canon 7D.

Basically very pleased so far - seems an excellent camera.

I agree about the DoF; even with my K20D I'm using f/9.5 - f/11 to get a good depth of field (it took me a while to realise I didn't need to use f/16+ as I'd been taught years ago for slides).

One of the other advantages is smaller size/lighter weight, both of the camera itself and the lenses - one of the things that puts me off 'FF', even if I can feel justified paying the higher prices involved. It will be interesting to see whether 'FF' cameras become the norm as they get smaller, lighter and more affordable (think e.g. ME Super + FA24-90), or whether advances in technology mean that smaller sensors can remain competitive in SLRs.

I don't have any experience of the Sigma or Tamron, but have the Pentax DA17-70 and FA24-90, and used to have the DA16-45. The 17-70 is the 'default' lens on my K20D (in the process of upgrading to K5) and is generally excellent - sharp, rich colours, and smooth bokeh - but it is the only lens that I've occasionally missed focus on (both auto and manual), plus there's some barrel distortion at the longer end (only really noticeable if you have a sea horizon or occasionally with architecture, and easily corrected in Photoshop etc). In terms of image quality I don't think there's much to choose between the 17-70 and 16-45, though I'd say the bokeh is better on the longer lens. I actually prefer the 24-90 to either (it's smaller and lighter too), but it's not really wide enough to be a standard walkabout lens. I expect I may be tempted at least to look at/borrow/hire the new DA* lens when it comes out.

Hearsay and speculation.

It's interesting that terms like 'full-frame' and 'APS-C' are ingrained in usage when the 'frame' of a digital camera is whatever size the sensor happens to be... (and I did grow up with 35mm)

I'm late catching up, but it's good to see an actual field test of the two cameras rather than speculation about the differences. John's review was too late for my buying decision, though it does support my thinking (a K5IIs, faulty unfortunately, arrived from SRS a couple of weeks ago).

My rationale was as follows (fully appreciating that other people will have equally valid reasons to come to other conclusions):

I've had a K20D for just over 4 years. I'm very pleased with it but I'd like to take advantage of some of the improvements available from the current generation of DSLRs - in particular better low light performance, better autofocus, more accurate metering, and probably a slight improvement in image quality (particularly under more testing conditions).

In theory I could stretch to a larger-sensor camera - but it means more weight plus investment in new lenses (I mainly do 'walkabout' photography and often carry my camera and sometimes an extra lens on long hikes). There's also the diminishing returns issue that John mentioned. I did look briefly at the APS-C competition (at least N & C), but there's nothing there that would tempt me away from Pentax.

So the obvious choice was one of the K5 variants (or possibly to wait longer for a 'K3' or whatever, and maybe a bit longer too to see if it's a real improvement or just an exercise in cramming more pixels on the same sized sensor - excuse my cynicism). Given that all are in my realistic budget range, I opted for the IIs on the basis that the 'II' has improved autofocus (which I'm using increasingly with my 17-70 and 55-300, having previously been a manual focus enthusiast), and the 's' may give improved image quality under some circumstances. The logic of short-cutting the process of desharpening in camera and re-sharpening post processing also appeals, and there seems to be enough evidence around that moire isn't an issue given that I'm not usually shooting fabrics or wedding dresses. And finally, the part-exchange offer from SRS meant that I could dispose of my much-loved if now worthless Olympus C5060, and feel I'd actually got something in return for it.

Now, I'm just waiting for the replacement to arrive so that I can get out in this sunny weather and start using it!