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11-10-2008, 02:19 PM   #1
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Anyone using Sigma 17-70mm with K20D?

After reading about the sensor of the K20D "outresolving" some of the older lenses, I wonder which of the following candidate lenses would be a better selection (I already have DA* 50-135mm and love it very much):

- Sigma 17-70mm f/2.8-4.5 (Even though this is not an EX lens, it is the most likely candidate for me IF the K20D is not outresolving it).
- Sigma 18-50 mm f/2.8 EX DC Macro (A bit pricy for me)
- Tamron 17-50mm f/2.8 SP XR Di II LD Aspherical (no experience with Tamron)

I do not consider the two obvious candidates from Pentax:
- 17-70mm f/4 SDM (because it is f/4 & because I haven't seen enough reports about its performance)
- 16-50mm f/2.8 DA* (It is pricy and replacing a poor copy in my country is too much of a headache; too risky).

I know many members have the lens in question. I wonder if they are happy with it ON THE K20D.

Thanks...

11-10-2008, 03:43 PM   #2
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I have the Siggy 17-70 and it's my main lens for my K-20d. I've never had issues with it's performance, and my AF is more accurate with it than with my Pen 28-105 (which I had to calibrate, unlike the Siggy, which worked right off the bat). It is a bit heavy, and it's only f2.8 on the wide end, but it's my go-to lens for when I know I have to get the shot.
11-10-2008, 04:51 PM   #3
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I am happy with my Sigma 17-70 on my K20D, but then I've never "checked" it. I just use it. Haven't noticed anything untoward.
11-11-2008, 04:32 AM   #4
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Just got my Sigma 17-20 yesterday for use with my K20D, but can't speak with any authority on its points, good or bad yet. It started raining here, so it may be a few days before I get a chance to really give it a workout. Soon as I do, I'll post my findings, etc. here.

-Morg

11-11-2008, 04:37 AM   #5
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I am VERY happy with it on the K20.


John
11-11-2008, 06:47 AM   #6
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Using it, loving it. It's my only autofocus lens (I'm using MF marvels for the rest of my kit) and I can vouch for its image quality, build quality, reliability.

The Sigma is actually f4,5 at 70 mm, based on your comment about the Pentax 17-70 being "only" f4 I thought you might not know that the Sigma is not a constant aperture. At 70 mm in very low light it CAN struggle if you don't know how to work with your AF system (provide contrast, for instance). Great for macro, even though it's not a 1:1 enlargment. Reading the reviews of the various lenses you're looking at in the user database of this website will let you know what people think about the lens.
11-11-2008, 07:15 AM   #7
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I got the Sigma 17-70mm recently and it is a very versatile lens, I dare say a little more versatile that the DA 16-45mm that I used to have. Pretty sharp lens on my K20D and the variable aperture is a minor issue. Don't know about the sensor outresolving bit, but to me the picture quality is good. Being a Sigma, go and test before you buy.
11-11-2008, 03:35 PM   #8
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I had the 17-70 on my K10D and now it is on my K20D and the IQ is very good, I would say better on K20D, but it is perhaps also the sensor

11-11-2008, 04:41 PM   #9
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QuoteOriginally posted by bdery Quote
The Sigma is actually f4,5 at 70 mm, based on your comment about the Pentax 17-70 being "only" f4 I thought you might not know that the Sigma is not a constant aperture.
But as soon as you move down from 70 it goes to f4, and then further down of course you can even get to f2.8, wonderful.
11-12-2008, 12:42 AM   #10
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Original Poster
Thank you all!

And, "fs999" thank you for your comment which really helped clearing my -perhaps unfounded- suspicion. Good to hear that the lens functions at least as good on the K20D.
11-12-2008, 01:08 AM   #11
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Thank you all!

And, "fs999" thank you for your comment which really helped clearing my -perhaps unfounded- suspicion. Good to hear that the lens functions at least as good on the K20D.
11-12-2008, 01:10 AM   #12
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The K20D & Sigma 17-70 make a great team. Very impressed with lens considering the low price. The only fault is the lens creep...but that can be fixed/serviced.
11-12-2008, 02:42 AM   #13
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QuoteOriginally posted by dazman Quote
The K20D & Sigma 17-70 make a great team. Very impressed with lens considering the low price. The only fault is the lens creep...but that can be fixed/serviced.
All Sigma 17-70s have a locking mechanism on the zoom ring to prevent the possibility of lens creep. On my copy I don't even need to use it as I don't have lens creep.
11-12-2008, 04:13 AM   #14
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QuoteOriginally posted by creampuff Quote
On my copy I don't even need to use it as I don't have lens creep.
Lucky you. After a service mine has gone from bad creep to half as bad creep. Wish the lock would work at every FL, not just 17mm. Still a great lens for IQ.
11-12-2008, 07:28 AM   #15
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I don't get creep as long as I don't put the hood on. When the hood is on, it definitely creeps when pointed down...
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