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03-17-2010, 01:47 PM   #1
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Sigma 18-50 or 17-70?

Hi,

I'm looking to upgrade my kit lens to something faster & sharper. I've been looking at the Sigma 18-50 2.8 & the 17-70 2.8-4.5. I have read the reviews and they both seem to rate well. The extra 20mm of range aside, is there anyone that has owned both and could give me an opinion about sharpness, & color differences between the 2?

Thanks!

George

03-18-2010, 04:23 AM   #2
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The first thing that pops out at me is the speed of each lens. The 18-50mm has a constant aperture of F2.8, which means it allows more light and lets you use a faster shutter speed indoors. The 17-70mm has a variable maximum aperture that gets smaller (larger number) as you zoom in, thereby slowing your shutter speed for the same shots. That's an important consideration depending on where you intend to use the lens most.

You could also consider the Pentax 17-70mm which has a constant maximum aperture of F4 and is very highly regarded as far as image quality goes.
03-18-2010, 06:43 AM   #3
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the 18-50 f2.8 is also a higher quality lens. Probably more sturdy and will have better IQ. Course it costs a bit more too. If your happy with the zoom from your kit then stick with the 18-50. You'll find while the extra bit of zoom helps, you'll end up using the extra stop of light a lot more
03-18-2010, 07:46 AM   #4
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Original Poster
Thanks for the replies. I was leaning towards the 17-70 for the extra reach but having that constant 2.8 really seems like it would be as or more useful. Any idea why Sigma doesn't say that their teleconverters are compatible with these shorter lenses? It seems like they can be used on every lens except for these short zooms.

I've read a lot of great stuff about the Tamron 17-50 2.8 as well. I get caught up in the minutia of this stuff & it's hard to make a decesion.

Thanks again!

George

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