Wide angle & general purpose lens

You'll find loads and loads of detailed comments on both the Sigma 10-20mm and Pentax 12-24mm if you search the forum's archives. I know from experience that the Sigma is good, and I know from reading that the Pentax is good, too.

Regarding the walkabout lens: There are zooms that go from 18mm to 125 to 200 or 250mm. Pentax/Tamron 18-250mm is often said to be the best of the superzooms. But it would be asking too much of a lens to go much wider as well while also proving long telephoto. The technology just isn't up to producing decent results with a range like that.

Regarding the speed of the Sigma 10-20mm. There is, or will be, a new faster version. It's bound to be much more expensive, and I expect larger as well.

Meanwhile, f5.6 at up to 20mm isn't really that bad. It's often fast enough for handheld indoor shots. Remember that you don't need particularly fast shutter speeds for such ultra wide angles. The viewfinder being a bit dimmer than it is with faster lenses is the only thing that bothers me about it, and that's not terrible.

Don't know about the wide angle lenses, so no comments on that.

For walkabout / holiday type lens I think that the 17-70 pentax or sigma would be advisable. Superzooms such as the 18-250 aren't lenses for everyone and they are quite heavy and large when fully zoomed out.

Pentax DA12-24mm is what I use, it's a very good lens, see the photo I posted on the Your Photos Forum "Windmill overlooking Flanders". I usually have my DA*50-155mm as a walkabout, but it is heavy and not a wide angle. I also think the DA18-55mm is a useful lens.

I recently owned & then sold the Sigma 10-20...whilst it's a good lens I found it didn't quite suit my style of photography. One comment I would make on it is that due to the Ultra wide aspect it does exhibit distortion, apparently the Pentax 12-24 is better in this respect.

If it's a general walkabout then I can highly recommend either the Sigma 17-70 or Pentax 17-70, I currently own both but will be selling the Sigma shortly

Simon

I think its worth making sure you are going to make the best use of a super wide lens.

I got my 10-20 on a vague idea that it would be great for landscapes but I found that unless there was something in the immediate foreground I ended up with wide open expanses of ground & sky with trees dotted along the horizon.

However the 10-20 is good for shots of buildings in tight places and I found it really useful at bus and car rallies where you don't have to wait patiently for people to get out of the way as you can take an excellent shot of a double decker bus from just a couple of feet away

It does work well inside although it makes rooms look a lot bigger (great for budding estate agents) but it really needs a separate flash as this big, wide, lens can easily create a large shadow from the on-board flash. It is also a pseudo macro lens as you can get very close to a subject.

Having said that I probably only take this lens out 2 or 3 times a year.

I wonder if it might be better to think about supplementing the kit lens with something longer and would recommend the Pentax 55-300 which can still be found at a very reasonable price (but probably not for much longer). The other thing to think about would be something faster than the kit lens and the 17-70 is probably a good idea or the 16-45 which can still be found at attractive prices. A DA*16-50 would be a desirable objective but these are becoming unreasonably expensive.

I have the Pentax 18-250 which I got 2nd hand to take out as a single lens when cycling or walking. However I have been a little disappointed with it. Wide open there is a bit of distortion and I end up having to correct the verticals in photoshop. At the long end the smallish maximum aperture means it is only best in bright sunlight.

There is a big danger, of which I'm very guilty, of building a large collection of lenses as "must-haves". One of the problems then is deciding which ones to take out on a particular day. I usually only want to carry two lens (one on & one off the camera) and very often I end up thinking that I've got the wrong lens on today! I've found that I now have a small set of favourites, 3 or 4 lenses, and many of the other ones hardly get used.

Glyn

It all depends on how wide you really want to go. My pentax DA 16-50 for me is wide enough for landscapes and so far in a short time of shooting with it, it has been a winner