Originally posted by veezchick I'm about to invest in some fast glass and am soliciting feedback. I'm torn between Sigma and Pentax lenses. My Sigma 105 is currently the best glass in my kit and I've read a
lot of horror stories on the Pentax SDM focus systems going out repeatedly, turning AF lenses into expensive manuals. In fact, there appears to be a consumer advocacy group petitioning Pentax to fix this problem.
These are the kits I'm considering: - Sigma 10-20mm F3.5 EX DC HSM
- Sigma 24-70mm F2.8 IF EX DG HSM
- Sigma 70-200mm F2.8 EX DG APO Macro HSM II (or Sigma 70-200mm 1:2.8 EX DG OS HSM)
- Sigma 30mm F1.4 EX DC HSM
Total ~$3,400 I've been in a similar position, and here are my experiences. I've got the:
Sigma 10-20mm F3.5 HSM
Sigma 17-50mm F2.8 OS HSM
Sigma 70-200mm F2.8 HSM II
Sigma 50mm F1.4 HSM
The 10-20/3.5 was to replace my Sigma 10-20/4-5.6. I always felt that my F4-5.6 wasn't the sharpest copy available, so I ended up replacing it with the F3.5 version. I could've gotten the Pentax 12-24/4, but it has no HSM, and the 2mm at the wide end makes quite a big difference.
The 17-50/2.8 won the choice between it, the DA*16-50/2.8 and the Tamron 17-50/2.8 as I was after an upgrade for my Sigma 17-70/2.8-4.5. The SDM issues steered me away from the DA*, while I had some reservations about the build quality of the Tamron, plus, the Tamron didn't have silent focusing, which the Sigma does with its HSM. I did also consider the Sigma 24-70/2.8 HSM, but I realised the 17-50mm focal range would have been more useful for the kind of work I do.
The 70-200/2.8 was a choice between it, the Tamron 70-200/2.8 and the DA*50-135/2.8 as I was after an upgrade for my Pentax DA 55-300/4-5.8 Once again, SDM issues meant the DA* quickly went out of the running. I think the Tamron is optically sharper, but reading of a few issues with it in terms of the aperture blades, and the fact that it didn't have silent focusing, meant I went with the Sigma.
The 50/1.4 was because I wanted a fast fifty, faster than the Pentax-F 50/1.7 that I had at the time. It was a choice between the Sigma 50/1.4, FA 50/1.4 or DA* 55mm/1.4. I ruled out the DA* due to price, and in the end went the Sigma route due to HSM, and it's performance.
In the ~30mm focal length range, I have the FA35/2, which is a fine lens, but I must admit, if the Sigma 30/1.4 in K-mount had HSM, I'd be saying goodbye to the FA and getting the Sigma. The Sigma 85/1.4 is out now, and that's something that I plan to be adding to my kit soon, with the FA* 85/1.4 not even in the running.
I've been shooting Pentax since the K10D, and had really high hopes about the DA*16-50/2.8 and DA*50-135/2.8 when they were announced and before they were released, both because they would be F2.8 zooms, and because they had silent focusing. But once they were out, their pricing, and the SDM failures really put me off. The pricing wasn't the major issue, since I was willing to save up for the lenses, but stories of SDM failures,
repeated SDM failures, the failure of Pentax to even acknowledge that there was a problem, all added up. As for weather sealing, I have used my Sigma lenses in light rain, and haven't had any problems, although I try not to have to do that, and I try to keep the lenses as dry as possible.
And yes, I do love my HSM lenses. I used to be content with screw-driven lenses and their noisy focus, because I didn't know better and ignorance is bliss, but as I shot more, and had experiences shooting in quite environments where the focusing noise draws attention, and when the photographers I knew all had that Nikon SWM and Canon USM lenses, I've made the switch and haven't looked back since; most of my HSM lenses have been upgrades from non HSM lenses. If you do go the Sigma route though, make sure you buy from a store that has a good returns policy, or buy from a physical store where you can test the lens out first, because there is a slight chance of focusing accuracy issues. My personal experience is also that Pentax lenses give a slightly warmer and more saturated look, and the colours are slightly better, but with the advent of digital processing, it's never been an issue for me.