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01-10-2011, 12:21 PM   #1
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Sigma 17-70 vs Tamron 28-75

I need some advice as I prepare to purchase a good solid walk-around lens. I'm new to Pentax and DSLR, having only recently purchased a k20d with an older kit (Samsung-label) 18-55 lens. I also purchased a M 50 1.7 and am slowly learning about manual focusing. I am moving up from a Panasonic FZ50 ultrazoom (35-420mm equivalent) and analyzing my pictures, I took a lot wide open at 35mm and many of my best "portraits" and people shots were taken around 100mm. I did use the long end some, and I plan to get a DA (L or not) 55-300 at some point to cover longer telephoto.

I think I've read every review here on the following lenses:

Tamron 28-75 2.8
Tamron 17-50 2.8
Sigma 17-70 2.8-4
Sigma 24-60 2.8
as well as the Pentax 16-50 and 18-135
As I do take a lot of indoor shots, I think I need the 2.8 aperture with my k20 to keep in reasonable ISO range. The Sigma 17-70 range seems ideal, but I worry that the long end won't be fast enough for indoor portraits, etc. On the flipside, everyone loves the Tamron 28-75 and the upper end would be fine, but is 42mm equivalent too wide? Is the Sigma 24-60 the middle-ground?

Seems like absolute IQ-wise, everyone would choose the Tamron 28-75 of this group, how much of a dropoff are we talking about to the Sigma 17-70? Undoubtedly I am over-analyzing this purchase, but I know I am on the beginning crest of LBA and want to make the right decision. After these two zoom purchases, I can see some primes coming my way (as $$ allow), perhaps the FA77, 35mm macro, 21mm, or 15mm - so I'd like to be "covered" in FL via zooms for the future. All opinions and recommendations appreciated, and thanks for all the great info here!

01-10-2011, 12:40 PM   #2
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A few things... Yes, you are overanalyzing things, but don't feel bad, we all do it. It's part of being a forum member.

Also, it's interesting to see how many of us (myself included) jumped into a Pentax DSLR straight from a Panasonic FZ.

I've had the older Sigma 17-70 for a little over a year. The 70 end is a little slow. I'm looking at trading it for a Tamron 17-50 as you may have read in another thread.

For indoor portraits, the FA50/1.4 is great. It's a good portrait length, but I personally would prefer something a bit wider.

I'm a bit confused about your question of the 28mm of the Tamron being too wide? Too wide for what?
01-10-2011, 12:42 PM   #3
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I know what I suggest... Tamron 28-75mm. The Sigma 17-70mm wouldn't be fast enough for me.
01-10-2011, 01:03 PM   #4
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I own both the Sigma 17-70 and the Tamron 28-75. For my money the 28-75 is a much superior lens. The Tammy is sharper, faster for most of it's range, and has better bokeh. I primarily use the Sigma when traveling or when making lens changes would be a particular pain. I also own the Tamron 17-50 and lately that lens has developed softness wide open to about f/4.0 or so. Don't know why. It will be going back soon. However b4 it's latest problems, I ranked it higher than the Sigma 17-70 also and for the same reasons mentioned above. I think either the Tamron 17-50 or the 28-75 is a better lens than the sigma. I personally would go with the 28-75 because I think those focal lengths are more versitile, but your preferences may vary.
For a good indoor prime I cannot recommend the new DA 35mm f2.4 more highly. It is a beautiful lens and is actually closer to f/2.2 in reality. It is both fast enough and wide enough for good indoor shots.

NaCl(hope that helps)H2O

01-10-2011, 01:26 PM   #5
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Thanks for the quick help... I guess those of us former Panasonic FZ-ers just always have to be a little different, and can see beyond the name on the front of the camera.

Sorry, lavascript, I meant is the Tamron 28-75 wide enough for me? 42mm vs the 35mm I am used to.

I think I'm leaning to the Tamron 28-75 at this point, I'll always have the kit 18-55 for the wide end if needed, and a wide prime may be first. Speaking of primes, having held a 12x zoom for so long, will I ever come around to using my feet for framing pics? I keep reaching for the zoom on the 50mm to get in tight on a portrait. Maybe I'm just not used to being as close to the subjects... With a main Pentax allure being the primes, I've got to figure it out.

Perhaps if I had a k5 and could easily go to 1600 or 3200 ISO I could live with the 17-70 on the long end, but I think it's off the list now. Thanks again for the input!
01-10-2011, 01:50 PM   #6
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if you can find a good copy of the Tamron, it should work well, but indoors, you'll find 28mm isn't wide enough. If they made a 24, it'd be a lot better.

Just MHO. Went through 3 copies of the Tamron and they had BF/FF/ghosting issues. Went through 3 copies of the Sigma and 2 of the 3 had decentering issues.

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