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05-31-2009, 05:39 AM   #1
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Sigma 17-70 f/2.8-4.5 || Pentax 17-70 f/4?

I intend to buy one of them to add to my Sigma 70-200 f/2.8, and while I lean towards the Sigma (for price), I might change my mind if given good reason.The purpose is general photography, as I want it to stay on the body most of the time. (Initially I'd go for something like 24-70 or 28-70, but the wider angle will come in handy.)

Two main points of concern for the Pentax one are:
(1) has no f/2.8 at all;
(2) is more expensive.

Another main point (3) is that I don't know how they compare in close-up (not macro) photography. It'd be good to know.

Any answers, additional advice and recommendations will be very useful and appreciated

05-31-2009, 06:08 AM   #2
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Why change your mind? The sigma is a fine is that of the Tamron 17-50/2.8.

Don't forget that Pentax offers a 16-50/2.8.

05-31-2009, 06:09 AM   #3
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I had the Sigma for a while. From memory it stays at F2.8 from 17mm to 23mm. So in the wide end it's faster. On the long end from 63mm the Pentax is faster. It also has pretty good macro feature. I don't think the Pentax has macro. On the other hand the Pentax has SDM motor and it's somewhat better sealed around the mount.
05-31-2009, 06:11 AM   #4
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I have the Sigma, and love it. It is very sharp throughout, has beautiful color rendition, and it's solidly built. I even bought the Pentax 18-250 over a year ago with the idea of replacing the Sigma with a more practical lens, and ended up keeping both, using the Pentax only for travel. (But I am not a good example, I also bought a cheap Tamron 28-75 for the 2.8, just in case!)

Anyway, to give you an idea of how sharp it is, it holds its own well against a Tamron 90/2.8 Macro. The top pic below is with the Sigma, the one below from the Tammy.

1/750s f/8.0 at 70.0mm iso200

1/500s f/11.0 at 90.0mm iso200

05-31-2009, 07:10 AM   #5
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I chose the Sigma over the Pentax because of price and am very happy with my decision, I would do the same now.

I wasn't interested in the weather sealing of the Pentax, but the one thing that I do appreciate about Pentax lenses is the 'quick shift' focussing ring which the Sigma's don't have. This wasn't worth the difference in price for me though.

Both lenses seem to be similar image quality and I'm sure you will be delighted with either.
06-01-2009, 09:29 AM   #6
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Original Poster
Thanks, guys, for the comments. I went with the Sigma and am very happy with it.

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