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05-22-2010, 10:54 AM   #1
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Pentax 17-70mm f/4 or Sigma 18-50mm f/2.8 or sigma 17-70mm f/2.8-4?

hi, guys,

i am completely new here but I am not that new of Pentax

Just wanna upgrade from the 18--55 kit lens, which one of the three do you think is better? Personally I like Pentax Lens, but it's a bit expensive, and sigma's f/2.8 seems to be better.

My main use is to shoot portraits and landscapes and my main problem with the kit-lens is it's in door performance, which brings a lot of blur...

thank you!

05-22-2010, 11:14 AM   #2
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I'd go with the sigma 17-70, as it's faster than the Pentax, and since it's sdm only, you don't want to risk any failures.
05-22-2010, 11:17 AM   #3
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I would go with the Sigma because it is by far the sharpest lens that I have ever used.
05-22-2010, 12:20 PM   #4
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The 18-50 is probably your best choice if you want to avoid blur in your images. I also advice you to learn how the SR works best, to ensure best sharpness.

Last edited by KjetilH; 05-24-2010 at 01:34 AM.
05-22-2010, 12:24 PM   #5
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Oh, and if you have a camera with SR then you don't need to get an OS lens anyways, I was talking about the original Sigma 17-70mm as well.
05-22-2010, 02:08 PM   #6
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Firstly, if you're trying to compare the little 18-55 with an f/2.8 lens, then it's unfair. The 18-55 is probably the best kit lens around. Once you get into f/2.8 territory, then it's another world of lenses altogether.

I'm certainly no fan of Sigma's glass, but their 18-50 and 17-70 aren't bad choices - I wouldn't call them the sharpest lenses available in this focal range, but they do perform well. The 17-70 offers you a slightly broader focal range, useful for portraits, but the 18-50 has the constant f/2.8 aperture that I think is more important.

If I were looking for such a lens, I'd also consider the Tamron 17-50 f/2.8, which I would rate better than the Sigma 18-50 f/2.8
05-23-2010, 04:12 PM   #7
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Interesting thread.
Just to add, what do you chaps think of the older Sigma 17-70 2.8-4.5?
I checked the favourable reviews in the lens database.

Looking at this for a cheapish upgrade to my kit lens, and the macro capability is attractive.

Don't want to hijack the thread, but thanks.

05-23-2010, 11:24 PM   #8
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Original Poster
thank you guys for the suggestions!

personally, i believe sigma ones are kinda better for the f/2.8, but i don't wanna risk to change 3--4 lenses to get a good copy so I'd go with the pentax 17--70. Also the pentax lens produces pentax-looking pictures which is VERY important. I guess the sigmas provide canon-like pictures.

i persuaded myself that what i really like is a pentax body+a pentax lens
05-24-2010, 05:30 AM   #9
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The Sigma 17-70 has many perks that the Pentax lacks. There are litteraly hundreds of topics in this forum about it.

Long story short, the three listed lenses are excellent by themselves. I believe the Sigma is the best purchase, however, for a general lens.

If you DO want a fast lens, then there's only one option on your list, really.

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