A great camera and a good choice. I'm sure you'll enjoy it.

With the depth of field you can get with wide angle lenses you may find there is less need for autofocus and/or quick shift, and that manually zone focussing is easier and faster - so HSM may have less relevance.

If you take a look at depth of field tables link, you will find that:
1) at 10mm a lens at F8 focussing on a subject 2' away should have everything acceptably in focus between 1' and infinity.
2) at 20mm a lens at F8 focussing on a subject 8' away should have everything acceptably in focus between 4' and infinity.

Price compares favourably, and although many seem to have had good service I decided to stay with a UK based purchase on the grounds that it's easier to sort out any potential problems

A 55-300 lens is certainly a good lens to start with - especially if you can pick up a good used copy. It shouldn't be too difficult to sell on again in a couple of years if you decide to upgrade.

If you're not aware there are 2 versions - the DA and the DA L

Optically they are the same

The DA has a metal mount, quick shift and a lens hood

The DA L has a plastic mount, no quick shift and no lens hood - but is the cheaper of the two

I've never heard of anybody having problems with the plastic mounts, and lens hoods on ebay can be had very cheaply, so it comes down to whether or not you need/want the quick shift.

You can see user reviews of the lenses here:
http://www.pentaxforums.com/lensreviews/

Between the two lenses you are looking at, there's not much of a noticeable difference between 300 and 320 at the long end. Personally I would find the extra between 55 & 80 at the short end much more useful.

Lens now acquired

Hi Mark,

Thanks for the comments and links, but yes, it is this specific lens I'm after.

Firstly, it's the constant F2.8 I'm after. That takes out the 17-70.

That leaves the Pentax, Sigma and Tamron 16/17-50 F2.8 lenses. I (sadly) discounted the Pentax on grounds of price, SDM issues (which may well be historic now) and reportedly sharper image quality of the other two. From there the choice is between the Sigma and Tamron. Looking at a number of reviews the Sigma generally seems to come out slightly ahead. Given that currently there's not a big price difference between them for a new lens, I've decided the Sigma is the one for me

Hi all,

I'm looking for a Sigma 17-50mm F2.8 EX DC HSM Lens in good condition.

Do any of you good folk have one you'd like to part with?

You could mitigate costs and maybe justify an 18-135 lens by looking at a Pentax K-30 instead of the K-50. Apart from the styling they are the same camera underneath, as you'll see in the conclusion to this review:
http://www.pentaxforums.com/reviews/pentax-k-50-review/introduction.html

and in this comparison
http://www.pentaxforums.com/forums/pentax-cameras-compared/?c1=k50&c2=k30#pentax...

SRS Microsystems have them for sale.

As you're not a novice photographer you may find this useful for lens comparisons:
http://www.pentaxforums.com/lensreviews/
The 18-135 is probably worth considering as well if it's within the budget - a more useful range than the 18-55 and generally reckoned to be better image quality.

I think it's Alan you need to welcome