Sigma EX Lens vs DC Lens

[Gianna'sPapa]

I recently purchased three new Sigma EX lenses (24-70mm f2.8 EX DG HSM, 70-200mm f2.8 EX DG HSM and 100-300mm f4 EX DG). The issue is the 24-70 is backordered and recently Sigma just announced the release of a 17-70 f2.8-4 DC OS HSM lens. The 17-70 is $450 cheaper than the 24-70mm. Both lenses will be in stock on the same date. The in-lens stabilization is not such an issue because I shoot with a Pentax K10d. I'm looking for a lens that is sharper than the Pentax 18-55mm kit lens for a walkaround lens with low light capabilities. I'm wondering if the EX lens is $450 better than their DC line of lenses. Any help or suggestions would be greatly appreciated. Thanks.

[cpbjgc]

I have the 17-70 for my Canon XTi and it is generally my walk-about lens. I also have an Sigma 30mm f1.4 which is an EX, and I would say that that the build is much more solid on the EX, though I don't see a huge difference in the image quality. What I really like about the 17-17 is the 17-20mm range, which I found that I used way more than I thought I would.

[handicap18]

The 17-70mm is a variable aperture, meaning the aperture gets smaller the more you zoom in. It starts at f/2.8 at the 17mm end, then probably around 20mm it starts to get smaller. f/4 isn't to bad and having OS is a plus. However, I've started converting to all f/2.8 lenses. IQ is generally going to be better. I have the Tamron 17-50mm f/2.8 and use it as my "walk-around" lens now. It replaced the Nikon 18-135mm and I really don't miss the longer focal length. The f/2.8 lens is FAR sharper than than my 18-135mm and for me that is enough.

I think that you will find that the Sigma 24-70mm f/2.8 to be a VERY sharp lens. It gets some real good reviews too. Personally I would go with that over the 17-70mm.