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05-01-2009, 08:52 PM   #1
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Pentax vs Sigma both 17-70mm

My next lens will most likely be one of these two lens. I know the Pentax version just came out and not may people have them. I also know that the Sigma 17-70mm is highly phrased lens on this board and other board.

I did a search and didn't get any info comparing the two lens. Many users benchmarked that sigma to the pentax 16-45/16-50/18-55(kit), tamron 17-50mm and against its down sigma 18-50mmf/2.8.

I know both lens have its pros and cons.

Pentax 17-70mm
The pentax has a better resale value and also it has the SDM. It is debatablie on if the SDM helps out or not. Also the Pentax use a smaller filter, 67mm vs 72 on the sigma. The only problem with the Pentax is that it cost about $150 more and it is a little bit slower at f/4

Sigma 17-70mm
The sigma lens is cheaper and a little bit faster. Personally I am not too concern with the f/2.8 because it is not constant

The two things that drives me is the price and the IQ of the two. Is the Pentax $150 better in IQ compared to the Sigma?

Also I have the Sigma 18-50mm f/2.8 EX lens as well. I want the 17-70mm lens because it gives me a longer reach because sometimes I find 50mm a little bit too short and I don't want or have time to change to a longer lens.

05-01-2009, 09:06 PM   #2
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QuoteOriginally posted by SuperAkuma Quote
The sigma lens is cheaper and a little bit faster.
The sigma is actually slightly slower where it matters: at the long end (f/4.5 vs. f/4 for Pentax).

Here's me picking and choosing favorable MTF50 stats on a K10D :

At f/4, 40mm, Pentax gives you
2028 (center), 1885 (border).

At f/4, 35mm, Sigma gives you
1888 (center), 1825.5 (border).

(from photozone.de)

Try also finding photos done with the Sigma and the Pentax shot towards the sun.
05-02-2009, 01:08 AM - 1 Like   #3
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there was a time when Sigma 17-70 had quite a following, many people were really into this len, and how sharp it was, etc...
Never heard that much about Pentax 17-70, it was announced, it came, some people got it and that was just about it, never some big WOW, or something..
looking at photozone tests, Pentax seems to be sharper wide open on wider settings, but stopped down, and at any f stop at longer settings, Sigma seems to be sharper. They have comparable barrel distortion, vignetting and Sigma may have edge in CA controll. Having said that, Pentax is partially weather sealed, and has SDM if those two matter to you...and still SMC is SMC!
tough call,

BR
05-02-2009, 01:52 AM   #4
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QuoteOriginally posted by axl Quote
Never heard that much about Pentax 17-70, it was announced, it came, some people got it and that was just about it, never some big WOW, or something..
Yes, we should always follow the wisdom of the herd...

05-02-2009, 02:37 AM   #5
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QuoteOriginally posted by asdf Quote
Yes, we should always follow the wisdom of the herd...
wouldn't we all be in Canikon capms?
05-02-2009, 02:55 AM   #6
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QuoteOriginally posted by axl Quote
wouldn't we all be in Canikon capms?
Shouldn't we? I mean, even Avril Lavigne owns a Canon. What the hell are we doing?
05-02-2009, 05:45 AM   #7
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Here's another review of the Pentax DA 17-70mm F4 just to add another POV to the discussion.
05-02-2009, 06:01 AM   #8
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QuoteOriginally posted by SuperAkuma Quote
My next lens will most likely be one of these two lens.
I tried them both out for a limited time (2 days is what the store allow), and ended up with the Sigma. It hunted less and was sharper at all apertures, but then maybe the Pentax I tried wasn't a perfect demo copy.

The Sigma is bigger (around) and heavier, but built like a tank. The Pentax felt a little cheap (unlike a DA*), but it does have "quick-shift to manual focus" which I sometimes wish the Sigma had.

05-02-2009, 09:26 AM   #9
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QuoteOriginally posted by weltschmerz Quote
Here's another review of the Pentax DA 17-70mm F4 just to add another POV to the discussion.
The 70mm f4 and f8 shots in test look more like motion blur to me, not lens softness.
05-02-2009, 09:44 AM   #10
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FWIW, if you have the Sigma, there's no reason to upgrade to the Pentax is what I concluded after looking at all the reviews and sample images. The Sigma is sharp and contrasty stopped down a little, though it looks sharper on the K10D than K20D (AA filter and higher resolution on the K20D).

If you have the 18-50, I'm not sure I'd bother upgrading unless you want to use the 17-70 as a vacation lens...
05-02-2009, 01:09 PM   #11
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QuoteOriginally posted by kenyee Quote
FWIW, if you have the Sigma, there's no reason to upgrade to the Pentax is what I concluded after looking at all the reviews and sample images. The Sigma is sharp and contrasty stopped down a little, though it looks sharper on the K10D than K20D (AA filter and higher resolution on the K20D).

If you have the 18-50, I'm not sure I'd bother upgrading unless you want to use the 17-70 as a vacation lens...
That was what I thinking taking about. The 18-50mm f/2.8 is a fantastic lens but sometimes it is a little short. Also I don't always need that fast of a lens when I am taking pictures outside during the day time or something along that line.

Thanks for the comment everyone else.
05-02-2009, 01:34 PM   #12
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QuoteOriginally posted by asdf Quote
Shouldn't we? I mean, even Avril Lavigne owns a Canon. What the hell are we doing?
LOL. I'm halfway curious how you know that fact. But the other half of me is thinking, man, I must have made a mistake going with Pentax!
05-02-2009, 02:49 PM   #13
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QuoteOriginally posted by asdf Quote
Shouldn't we? I mean, even Avril Lavigne owns a Canon. What the hell are we doing?
You're right - we should come to our senses!

Jer
05-02-2009, 06:12 PM   #14
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QuoteOriginally posted by weltschmerz Quote
Here's another review of the Pentax DA 17-70mm F4 just to add another POV to the discussion.


https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/55729-doing-wr...eview-com.html
05-02-2009, 07:01 PM   #15
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I have actually done a quick comparison between these two lenses. On my K20D, the Sigma 1770 does seem to be a better lens, sharper at almost all focal length and aperture settings except at the very wide end where the Pentax one is sharper wide open, but it's quite a bit slower than the Sigma at that focal length. When set at the same aperture, can't tell much difference.

The Sigma has better CA control over the entire focal range, and it can focuse even closer than the Pentax. The Pentax has SMC, but the Sigma doesn't have much flare problem either.

And as panoguy said above, the Sigma 1770 does feel slightly better built than the Pentax one, although the Sigma's zoom needs sometime to get used to (turning opposite direction).

I'd go w/ the Sigma if I were choosing betwen these two.
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