[FrankC]

To compare lenses regarding resolution and other factors take a look at www.photozone.de This might change your mind about getting the Sigma. I agree with the other posts that the Sigma tends to break more than other brands. When I worked at a retail photo store in the late 90s, I noticed that Sigmas came back far more than any other brand.

[jezza323]

I wanted to get the Pentax 12-24mm when I was shopping for a wide angle, but the cost was too high. It is reported to be the sharpest though. Also, after having the 10mm available, I think I would miss the wide end (I mostly shoot at either 10 or 20mm with the sigma, rarely in between). The difference from 10-12mm is quite large.

The newer Sigma (f3.5 version) has stupid size filters (82mm from memory) which are hard and expensive to get, so that ruled it out. The wider Sigma 8-16mm is stupidly wide, and quite expensive, and doesnt really work with filters at all. All reviews I read on the Tamron 10-24 reported it was softer than the old Sigma.

And to top off my decision, the Sigma 10-20 f4.0-5.6 popped up for sale on ebay at the right price (Buy It Now) so I couldn't say no then!

At some stage I would still like to add a prime diagonal fisheye to my collection though. For the REALLY wide and fishy views

While everyone has mentioned problems with Sigma QC, I have never had any trouble with any of my Sigmas, which were both 2nd hand when I bought them. Not saying its not a problem, but just saying it has not been for me

[FrankC]

Fisheye uh? That's a fun lens to use. I had one when I used Canon. Just be careful because the affect is quite obvious and strong, and it can get gimmicy real quick if not done carefully. It'll be awesome for stitching panos inside and outside.
82mm is a flippin' huge filter size! I can feel your concerns since I just got a 35mm for my 645D which has 82mm. I, fortunately, know people who can get me filters at dealer cost which made my decision to get the lens much easier.

Just remember the old antage: "It's not what you have, but you do with it."
Keep shootin'
Frank

[gp1806]

Another vote for the Sigma 10-20 f4.0-5.6. I've had no problems with mine.

[interested_observer]

While you are trying to decide which lens, take your 17-70, use it in portrait mode at 17mm and take stitched panoramas. Use Microsoft ICE to create the final "wide" image (its a free download). Take sets of 2, 3 or 4 shots wide. They will be much wider than any UWA lens.

• Microsoft Research Image Composite Editor (ICE)

[jezza323]

While you are trying to decide which lens, take your 17-70, use it in portrait mode at 17mm and take stitched panoramas. Use Microsoft ICE to create the final "wide" image (its a free download). Take sets of 2, 3 or 4 shots wide. They will be much wider than any UWA lens.

• Microsoft Research Image Composite Editor (ICE)

This is a good option too if you have the patience. Here are some of the stitched panoramas I did with my DA 18-55mm before I got my Sigma 10-20mm

[Jetfin]

I have a Pentax 12-24 that lives on one of my K200D's. It's a great combination for landscapes. But, I think any of the lens mentioned in this thread would work well for you. Good luck with your choice and future business.

[Neel1]

Finally, I think I will be opting for Tamron 10-24 because it has a more reasonable price and I can only order through the internet. Here in Mauritius, prices of lens are really too high compared to elsewhere and resellers pratice around 150% price compare to elsewhere.

But when I buy online, I cannot exceed a certain amount or else I have to pay some extra charges with custom taxes, etc!! So it will be a Tamron 10-24. Reviews are good for that one!!

[DaveHolmes]

I don't think there's a wrong decision here; as such I think you'll love the Tamron (they have a reputation for making sharp lenses)...

For me it'd be the Tamron or the DA15mm...