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07-11-2010, 02:18 AM   #1
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Downsizing; which 17-70mm to buy...

I've been putting this of for too long. Last year, I travelled to Vietnam with the K100D, 18-55 and 55-300 lenses I had at the time. It was the first trip I used an SLR on, and it was great. But... the 18-55's reach was, at times, too short, it had too much vignetting at wide-angle and the sharpness was not very good, except when stopping down to f/8, which I did most of the time.

I could have bought a 17-70 after the trip, and I thought about it, but in the end, I went a different route. I bought a Pentax-A 50mm f/1.7 prime, a Tamron 28-75mm f/2.8 zoom, and (after having tried a superzoom) a Pentax-DA 16-45 f/4 zoom. I also upgraded to a K-7 and sold my K100D and 18-55, along with a few 52mm filters I bought along the way.

About a month ago, I travelled to Romania with the body and 3-zoom set, and took some great pictures. I really liked the image quality I got. But... I don't like having to carry three lenses around. A 2-zoom set was ok, but a body and 3 lenses (which also happen to weigh more individually) in my beltpack was, at times, not so comfortable.

So, I want to downsize. But I really don't want to give up much of the image quality, especially after having upgraded to the K-7. The 50mm prime was a good buy. It's not as convenient as a zoom, and sometimes it gives me a hard time focusing (have to get a decent focusing screen for the K-7). But it's small, light and very fast. However, the 16-45 and 28-75 are a different story, with a combined weight of over 900 grams.

So, I'm kind of back to where I was last year, wanting a 17-70. But, like I said, I want it to replace the 16-45 and 28-75. So it should be a good-quality lens. I have looked at the Sigma and Pentax lenses, and from a value perspective, the Sigma wins. f/2.8 at the short end, semi-macro abilities... this looks good. But, according to Photozone reviews, the Pentax beats the Sigma in terms of sharpness. And I really don't want to have to stop down the lens to get acceptable sharpness, because I don't want to go over f/4 or f/4.5 for portraits.

I know that graphs and numbers in reviews often don't tell the whole story. It's just that I keep thinking "the Pentax must be sharper/better/etc.". Is it, significantly so? Or did Photozone just get a bad sample and am I worrying over nothing?

07-11-2010, 03:17 AM   #2
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If you want to sell your Tamron, I am in the market for one

Regarding your choices, I would avoid Pentax SDM lenses and go to Sigma anyway.
07-11-2010, 04:08 AM   #3
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I've heard of SDM lenses failing, but I figured you probably won't here from people whose SDM lenses work fine. Have you experienced a failing SDM drive yourself?
07-11-2010, 05:01 AM   #4
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the answer to "which 17-70" depends solely on personal preference. for example, i have the pentax lens so i am going to say - go with pentax because it rocks! while someone who has a sigma lens will tell you - sigma rocks so go with that lens!
so at the end of the day it's your money and you'll have to make the decision, regardless of what anyone else says.

as far as SDM failures go, sure, it is possible that it will fail and you will have to have the lens repaired but the same could be said about sigma HSM and canikon whatever-they-call-their-ultrasonic-drives.

the bottom line is that all newer lenses contain electronics that are prone to failure. it's a fact that you have to except, live with, not worry about too much, and just enjoy using your lens instead.

good luck!

07-11-2010, 05:59 AM   #5
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QuoteOriginally posted by pb_red Quote
the answer to "which 17-70" depends solely on personal preference. for example, i have the pentax lens so i am going to say - go with pentax because it rocks! while someone who has a sigma lens will tell you - sigma rocks so go with that lens!
so at the end of the day it's your money and you'll have to make the decision, regardless of what anyone else says.

as far as SDM failures go, sure, it is possible that it will fail and you will have to have the lens repaired but the same could be said about sigma HSM and canikon whatever-they-call-their-ultrasonic-drives.

the bottom line is that all newer lenses contain electronics that are prone to failure. it's a fact that you have to except, live with, not worry about too much, and just enjoy using your lens instead.
While I am also considering the non-HSM version of the Sigma lens (because it's lighter, smaller, focuses closer and I already have body-based SR), you are absolutely right and I'm not going to worry over if's and maybe's concerning SDM/HSM.

I think I would rather have the Pentax lens. It gets better Photozone ratings, the zoom/focus rings turn in the right direction and it's a genuine Pentax lens. But... it costs so much more. And they don't get offered a lot second-hand. Plus the Sigma has better macro abilities.

I might buy either one if I spot a good offer though.
07-11-2010, 10:32 AM   #6
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QuoteOriginally posted by starbase218 Quote
While I am also considering the non-HSM version of the Sigma lens (because it's lighter, smaller, focuses closer and I already have body-based SR), you are absolutely right and I'm not going to worry over if's and maybe's concerning SDM/HSM.

I think I would rather have the Pentax lens. It gets better Photozone ratings, the zoom/focus rings turn in the right direction and it's a genuine Pentax lens. But... it costs so much more. And they don't get offered a lot second-hand. Plus the Sigma has better macro abilities.

I might buy either one if I spot a good offer though.
Starbase... who much do these lenses cost in Europe? A quick check of B&H in New York reveals the Pentax 17-70mm f/4 is offered for US$479.99... the Sigma 17-70 f/2.8-4.5mm DC is US$369.00 and the Sigma 17-70mm f/2.8-4 DC OS HSM is US$449.00. I understand European prices are often higher... but it seems these three lenses shouldn't be that far apart.

17-70mm Lens for Pentax
07-11-2010, 03:06 PM   #7
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According to kieskeurig (Dutch pricewatch site), the Pentax 17-70 f/4 can be found for €470, the Sigma 17-70 f/2.8-4.0 for €340 and the Sigma 17-70 f/2.8-4.5 for €280. It seems the Pentax is significantly more expensive here than in the US.
07-11-2010, 06:58 PM   #8
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QuoteOriginally posted by starbase218 Quote
According to kieskeurig (Dutch pricewatch site), the Pentax 17-70 f/4 can be found for €470, the Sigma 17-70 f/2.8-4.0 for €340 and the Sigma 17-70 f/2.8-4.5 for €280. It seems the Pentax is significantly more expensive here than in the US.
Yikes, that is significantly more. Given that you already have the DA 16-45 with a constant f/4 aperture, I would have no problem going with the less-expensive Sigma 17-70 f/2.8-4.5, especially considering you have image stabilization in the camera body. That f/2.8 at the wide end combined with the lower price makes it a pretty attractive proposition. But I notice that this lens is "temporarily unavailable" at B&H. I hope that really means "temporarily" and doesn't mean its going out of production. Maybe you should act sooner rather than later.

Meanwhile, if you're interested in the more-expensive Sigma 17-70 f/2.8-4 DC OS HSM... make sure before you buy that the Pentax-mount version includes HSM. There are some Sigma HSM lenses that don't include that feature in the Pentax mount. One example: the 30mm f/1.4 prime. I'm not saying that's the case with this lens... I'm just saying make sure you're getting HSM if you're paying more for that Sigma.


Last edited by Biro; 07-11-2010 at 07:08 PM.
07-11-2010, 08:19 PM   #9
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I have the Sigma 17-70 2.8-4.5

I find the 2.8 at 17mm handy indoors as I don't have any other lenses yet. Also the 1:2 "Macro" is great.
As a walkaround I find the 70mm still a little limiting and in the same sentence not significanly longer than 50mm. Having said that the 70mm on APSC does nail across the road shots . Have you considered the Sigma 18-125?
One thing that threw me on the Sigma from first use is the focusing noise so if that worries you then go the Pentax.
07-24-2010, 12:14 PM   #10
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Well, I've decided and bought the Pentax version. I pre-ordered both and compared them at the shop. The Pentax was significantly sharper, particularly in the center but also in the corners, at f/4.5 at 70mm. Even at f/4, it was still sharper than the Sigma at f/4.5. Since I consider large-aperture performance at 70mm important, I choose the Pentax. Also, I feel colors were slightly better with the Pentax. It was far more expensive, but since I intend it to replace the 16-45 and the 28-75, I feel the higher price tag is justified. Besides, I got two years warranty (which I consider insurance just in case the SDM fails).
07-25-2010, 03:22 AM   #11
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QuoteOriginally posted by starbase218 Quote
It was far more expensive, but since I intend it to replace the 16-45 and the 28-75,
What? You bought the 17-70 to replace your 28-75? I'm thinking about doing the opposite, replacing my 17-70 with 28-75...
07-25-2010, 03:38 PM   #12
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QuoteOriginally posted by simico Quote
What? You bought the 17-70 to replace your 28-75? I'm thinking about doing the opposite, replacing my 17-70 with 28-75...
Damn, I should have known... we could have swapped!

I might actually keep the Tammy for now. But the 16-45 is for sale.
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