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Old Mar 29, 2007, 5:14 PM   #1
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I plan to purchase one of these three lens in few weeks, the Tamron 17-50mm F2.8, Sigma 18-50mm F2.8 and Tokina 16-50mm F2.8, for now the Tokina doesn't have the the minolta AF mount, the price will be very high if they do compare with other two.

I have to make the choice between the Tamron and Sigma, I am only concern for the over all picture quality.

I need recommandation from all of you. Thanks
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Old Mar 29, 2007, 7:10 PM   #2
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The users at DYXUM.Com seem to prefer the Tamron over the Sigma, and Popular Photography gave it their Editor's Choice Award.
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Old Mar 29, 2007, 7:25 PM   #3
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Have you seen the user reviews for these lenses here?

http://www.dyxum.com/lenses/results.asp?IDLensType=3

If cost is not an issue the Carl Zeiss 16-80mm is starting to become available. Nice range but you give up f/2.8 of the Tamron and Signa.

I have a Tamron 17-50mm and really like it.

--FrankD
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Old Mar 30, 2007, 5:57 PM   #4
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I ordered the Tamron yesterday. Thank you.
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Old Apr 5, 2007, 5:43 PM   #5
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I received the Tamron 17-50mm F2.8 today and try it right away, but I discovered some problems:

At 17mm and 50mm both at wide open F2.8, the pictures are sharp, but anywhere between the pictures are not sharp at all until step down to F5.6.

Do I have a bad lens? I am thinking to send it back for another lens.
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Old Apr 6, 2007, 6:50 AM   #6
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lsifs wrote:
Quote:
I received the Tamron 17-50mm F2.8 today and try it right away, but I discovered some problems:

At 17mm and 50mm both at wide open F2.8, the pictures are sharp, but anywhere between the pictures are not sharp at all until step down to F5.6.

Do I have a bad lens? I am thinking to send it back for another lens.
Isifs,

I shot some pictures of a lens test chart used my Tam 17-50mm. Shot at 17mm, 22mm, 30mm and 50mm at f2.8. There is no appreciable difference between them other than camera alignment. My test method is a little crude (camera on tripod, test chart taped to the side of a box) and it is difficult to maintain perfect geometric alignment.

It sounds like you may have received a bad copy of the lens.

What are you using for a test subject?



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Old Apr 6, 2007, 7:38 AM   #7
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Isifs,

Another thought. Have you read this thread?

http://www.stevesforums.com/forums/v...=84&page=2

If you are changing your zoom setting without re-focusing it might be a problem.
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Old Apr 7, 2007, 11:07 AM   #8
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Thanks for advice, I will try again with enought light and use tripod to avoid the hand shakes.
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