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08-29-2008, 02:57 PM   #1
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Sigma 17-70 or Sigma 18-50 EX F/2.8

Hello I am a long time lurker, but am considering buying a new lens and wanted some advice. I am considering one of the above lenses as I am sick of the kit lens that came with my k10 (in truth I use the short end of the pentax f 35-105 as it operates as a "normal lens" and has the macro function) and feel it is worth an upgrade. I enjoy taking photos of landscapes, architecture, the occasional night shot and so long zooms are not really an issue ( I have the 70-200 if needs be anyway for the 15 minutes of interest I have in trying to take pictures of birds once everywhile - wish they would stay still). Both lenses are near enough the price of each other but am finding it difficult to choose between them and so need some help!

**** Also the Tamron 17-50 has been suggested as an alternate, so thoughts on that if there are any! Many thanks!!

ps// If you want to throw me and recommend another lens alltogether please feel free but only in the price range of the above two.

pps// many thanks!

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Last edited by; 08-29-2008 at 04:05 PM.
08-29-2008, 03:16 PM   #2
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I have both the Sigma 17-70 and the 18-50 2.8 Macro. I kept the 17-70 because it is such a sharp lens and I use it as a walk-around lens on my K200. The 18-50 has become my favorite lens for indoor shooting because of the constant 2.8 in lower light conditions. I also used it on a recent trip to Alaska to shoot sunsets.

You can't go wrong with either one, it just depends if you want the 2.8 for the whole range of the lens. The 18-50 I have is the newer one with the Macro designation.

This sunset shot was taken with the Sigma 18-50Macro at 10:18 in the evening so the lighting was very low.

08-29-2008, 03:28 PM   #3
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My next 'big' trip is Japan and I expect I will want to shoot indoors in temples, museums etc and the constant f2.8 would be great for that. I don't think I would miss the extra 20 at the long end, nor the 1 at the short end. But if the difference in quality is not too different between the two then the 17-70 is more versatile... Argh! driving me bonkers
08-29-2008, 06:53 PM   #4
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I got the Tamron 17-50 f2.8 and boy is that a sharp lens. I also have the 50mm f1.4 from Pentax and I still think the Tamron is sharper. The focus ring is nice and fat, great for manual focusing. However, if you are going to need 20 more mm on the long end, then you should pick out the 17-70. Otherwise, get a 1.4x Tamron teleconverter with te 17-50.

08-29-2008, 10:53 PM   #5
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All three lenses you mention are good.
I think any of them will suit your intended use well.
08-30-2008, 09:27 AM   #6
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probably leaning on the one of the Sigmas because of the addition of the Macro function. Not full decided though!
08-30-2008, 12:04 PM   #7
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is the tamron constant 2.8?
08-30-2008, 12:19 PM   #8
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Brian, please see PM I sent, thanks,
FHPhotographer (Brian L)

08-31-2008, 04:23 AM   #9
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I used to have sigma 17-70 but sold it with my K100D to my friend. I was considering buying Pentax DA* 16-50, but at my test shots Sigma 18-50 beat it at any focal lenght wide open (using K10D) and since I had shooting coming up in few days I bought Sigma 18-50, though with little hesitation. Well, some 600-700 shots later I'm very pleased with it. I previously thought that Sigma 17-70 was sharp, but little did I know, 18-50 is sharper yet. Most important for me is that it's sharp right from f2.8.

Sharpness, clarity, contrast and colors are visibly better than with 17-70. At times the image quality scarily approaches my FA50 f1.4. 18-50 bokeh is smoother than that of a 17-70, weight, feel and handling is about the same. There have been few times when I wish I had longer reach than 50 and better magnification (17-70 has 1:2, 18-50 1:3), but within its range the 18-50 clearly tops 17-70 for image quality. 17-70 itself is remarkable lens and you can't go wrong with it, but constant f2.8 does come handy, especially when it's sharp across the range.

I don't shoot brick walls or test charts so others may have different opinions though.
08-31-2008, 03:32 PM   #10
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After much agonising and the counsel of my (patient) friend I went for the Tamron, like someone has said they are all good lenses but the slightly better IQ reports and the extra few mils at the short end sold it for me.

Thanks for the advice!
08-31-2008, 07:46 PM   #11
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Congrats. You will enjoy the Tamron as I have. It is easily the sharpest lens in my arsenal.
08-31-2008, 08:22 PM   #12
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I have the sigma 18-50mm EX f2.8 macro - it is one of my favorites specially for night shots indoor. The constant f2.8 is important for flash photography; I don't know about the sigma 17-70mm - most review I have seen were good to excellent if you can get a good copy. Well, if the sigma 17-70mm is also EX glass(supposedly means better grade) and you need more on the long end, I would suggest you go for that one instead of the 18-50mm (sigma or tamron). For me, I don't need that since I have a 77mm Ltd prime along with this lens for night flash photography.

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