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06-11-2012, 07:02 PM   #1
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please advise..

Hi all, I am thinking about buying either Tamron AF 90mm f/2.8 SP Di macro or Sigma AF 70mm f/2.8 EX DG macro. Originaly I was going to buy pentax 55-300, but was told that if I crop the picture from either of the two other lenses, I would get a better result, better IQ. Would you agree? Which of the two would you recomend? Thanks, regards Danny

06-11-2012, 07:16 PM   #2
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QuoteOriginally posted by zdeneczech Quote
Hi all, I am thinking about buying either Tamron AF 90mm f/2.8 SP Di macro or Sigma AF 70mm f/2.8 EX DG macro. Originaly I was going to buy pentax 55-300, but was told that if I crop the picture from either of the two other lenses, I would get a better result, better IQ.

"Digital zoom"?

I don't think so, especially at 300mm.
06-11-2012, 07:18 PM   #3
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Between the zoom and those primes they are totally different applications. What are your needs?
06-11-2012, 07:22 PM   #4
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You will be able to crop more with the 90mm, but not enough to compare with the 55-300 @ 300mm. They are very different lenses, so you need to think about what you want the lens for. If you are shooting macros or short tele portraits, the Tamron would be excellent and can do things the 55-300 can't. However, if you aren't shooting macro and you prefer more of a walk around, wildlife, or sports lens, then the 55-300 would be a lot better. There are better sports lenses than the 55-300 in terms of f-stop and autofocus speed, but they are a lot more expensive and a lot heavier.

06-11-2012, 07:52 PM   #5
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QuoteOriginally posted by zdeneczech Quote
Hi all, I am thinking about buying either Tamron AF 90mm f/2.8 SP Di macro or Sigma AF 70mm f/2.8 EX DG macro. Originaly I was going to buy pentax 55-300, but was told that if I crop the picture from either of the two other lenses, I would get a better result, better IQ. Would you agree? Which of the two would you recomend? Thanks, regards Danny

Not even close. Whoever told you this is completely full of sh*t.
06-11-2012, 08:01 PM   #6
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As has been said, those are totally different lenses, and whomever advised "digital zoom" is just wrong. Cropping for enlargements works IF we compare a lens to that same lens with a teleconvertor (TC) added. So if you thought to use the Tamron 90 with a 2x TC, you would probably get better results WITHOUT the TC, just by cropping. But a shot taken with the DA55-300 at 300mm would look MUCH better than a cropped shot from the Tamron.

Again, it depends on your needs. If you are posting pictures on Facebook, image quality (IQ) is not so important. If you wish to make small prints, like around 10x15cm, IQ doesn't matter so much. But for any larger print or display, IQ *does* matter, and you do *not* want a "digital zoom" effect.
06-11-2012, 08:03 PM   #7
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QuoteOriginally posted by zdeneczech Quote
Hi all, I am thinking about buying either Tamron AF 90mm f/2.8 SP Di macro or Sigma AF 70mm f/2.8 EX DG macro. Originaly I was going to buy pentax 55-300, but was told that if I crop the picture from either of the two other lenses, I would get a better result, better IQ. Would you agree? Which of the two would you recomend? Thanks, regards Danny
Not a chance.

I suspect you are confused between putting a TC on a lens vs cropping an image from that same lens. Then it could be close, but in the case you describe, cropping a 90mm lens to 300mm, then the 300 will be better in almost ever case imaginable.
06-12-2012, 01:20 AM   #8
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You could debate about cropping from DA*200/2,8 compared to DA55-300 and that could make sense. But in case of these two short tele it is complete nonsense.
DA55-300 is quite sharp at the long end. Sharper than most other xx-300 zooms.

06-13-2012, 07:27 PM   #9
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55-300

Thanks guys, well I am just trying to avoid lugging too many lenses with me. Ill have 16-45, 35mm, and either tammy 90, sigma 70 or pentax 55-300. But it seems that because I like to take pictures of animals, birds etc I will have to buy 55-300 and buy sigma or tammy later, Danny
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