Limited primes are too much, and we'd get fed up of constantly changing lenses.

Kilburn, sounds like you're in the same boat as me.

The Sigma ticks the boxes because it seems better "all around" - quicker, slightly more range, quicker to focus.

Thanks John, Defragged.

The 18-125mm is tempting but all the all-in-one lenses seem to get criticised.

I really like my FA 50mm f/1.4 for the speed but I'd love to be able to zoom around a little.

David, thanks for your reply. My previous post must have crossed yours.

Looking at the Pentax Forums review it seems the newer Sigma might be a better choice...

One thing I like about it in the reviews is the faster AF and reduced hunting.

The faster speed at the wide end also appeals...

Thanks Blythman. I really like the look of the Tamron, but yeah, I think my wife would miss the extra room at the top end.

I'm considering replacing the 18-55mm kit lens.

I would like something a bit faster with the potential for some portraiture. My wife wants something faster but would also like a bit more range. I've been looking at:-
- SMC Pentax-DA 17-70mm F4 AL [IF] SDM
- Sigma 17-70mm F2.8-4 DC Macro HSM
- Sigma 24-70mm F2.8 IF EX DG HSM
- Tamron 28-75mm F2.8 AF XR Di LD Macro SP

To my mind the new Sigma 17-70mm seems like a decent option. I think I'd rather have the wider part of the zoom and give up on the extra speed of the constant f2.8 offerings

Has anyone compared 2 or more of the candidates?

Nice set. No 2 is cracking.

Thanks Yves

On my K-5, often I want to fix focus by half-pressing the shutter button, and then I want to shift the framing of the shot.

If I try that currently, the camera continues to try and auto-focus. I'd prefer if focus "locked in" on the half-press. Does that make sense and is it possible?

Have you tried it off-camera?

I've just got one too, but the only way I can get it to trigger in sync with the K-5 is by setting the K-5 for regular flash (as opposed to, say, wireless) and then setting the flash to S2 mode.

All other combinations, the flash goes off but not in sync.

Touche. Hehehe. Yeah, which part? Spending time on forums, or applying some thought?