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12-07-2011, 04:11 PM   #1
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Tamron 17-50mm f2.8 Focus problem

I have a Tamaron 17-50mm f 2.8 lens, it is giving me a bit of grief.
At f 5.6 and above the lens produces a good sharp photo but below f4 the picture on the left side is very blurry and out of focus, I know I should expect a bit of softness at f2.8 but not this much and at f4 the picture quality should be better. Here's an example look at the little tree left side.

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12-07-2011, 04:56 PM   #2
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Normally I would say that the lens is busted; however, it looks like you focused the lens on the end of your house, and thus I'm tempted to say that this is a DOF issue. Try shooting a picture of a test chart.

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12-07-2011, 05:28 PM   #3
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I focussed on the chair which was about the same distance as the tree from where I was standing.
I have better photos but can't upload any more as I'm about on my limit. but you can see my post here with photos.
Tamaron 17-50mm f2.8 lens focus problems: Pentax SLR Talk Forum: Digital Photography Review
12-07-2011, 05:49 PM   #4
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This does not look like a DOF issue to me. The trees and shrubs on the right lie in the same plane as the tree on the left.
Likewise with the grass to the bottom of the frame. My Sigma 10-20mm has the same issue, and most likely is affected
by the lens element that controls internal focusing. You could try to shoot a series of the the same scene at the same f/stop and
manually change the focus point from near to far. You might see how sharpness/blur changes/varies from the left to right side.
A newspaper at a perpendicular angle would also make a good target, once again confirming focus at the center and then slightly
changing focus from near to far. If the lens is decentered, it will become obvious.

12-07-2011, 06:21 PM   #5
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Thanks about your tip about the newspaper, you can really see it. Top photo is f2.8 bottom one is f8, I had trouble holding camera square on to the paper so the top of f2.8 would have been worse. I must tape a page to the wall when the seller wants more proof of OOF.
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12-07-2011, 06:49 PM   #6
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Get the lens exchanged

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12-07-2011, 06:53 PM   #7
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This looks like a de-centering issue with the lens; that is, the left side is softer than the right side even though they both are in the same focal plane. Also, you have indicated that the focus point is on the chair which is on the left side; this is even more severe than if the focus point is in the center.
12-07-2011, 08:07 PM   #8
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QuoteOriginally posted by Adam Quote
Get the lens exchanged
Agreed!
As mentioned, it does appear to be de-centering issue. I had the same exact problem with this lens.
Looking at the OP's sample photos I can almost swear it's the same exact lens I returned for this very problem.

12-07-2011, 08:16 PM   #9
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QuoteOriginally posted by K57XR Quote
Agreed!
As mentioned, it does appear to be de-centering issue. I had the same exact problem with this lens.
Looking at the OP's sample photos I can almost swear it's the same exact lens I returned for this very problem.
Thanks, did you end up getting another Tamaron 17-50mm lens? I noticed that my serial number is 020536 I wonder is that old stock.
Just going to get back to the EBay dealer and ask for a refund as they state they have a 7 day refund policy.
12-07-2011, 08:34 PM   #10
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QuoteOriginally posted by ross Quote
Thanks, did you end up getting another Tamaron 17-50mm lens? I noticed that my serial number is 020536 I wonder is that old stock.
Just going to get back to the EBay dealer and ask for a refund as they state they have a 7 day refund policy.
It was actually the second copy I returned and decided against a third. The first one was excellent across the frame but there was some sort of white contaminant inside the front element sitting on the center of the inner glass. It wasn't dust but something bigger. I was surprised it didn't show up on pictures.
If you decide to get another copy I'd suggest buying it from a reputable store with plenty of stock where you can keep exchanging until you get a good one (plug---Adorma or B&H)
12-07-2011, 09:01 PM   #11
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I just got an e-mail from the dealer in Hong Kong he wanted to know how much would it cost to get a Tamaron Agent here to adjust the focus on the lens. So I phoned the service center in Australia which handles Tamaron Optics, he said if it was to do a realignment of the internal lenses or something to that effect, it would cost $110.
He also added they have the right gear to do such an adjustment, they purchased it from Tamaron.
I think I wouldn't mind sending it away to get checked out thoroughly for optical alignment , as there is no gaurantee if I get another one that that will be any better.
12-07-2011, 09:54 PM   #12
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What about Tamron's 6 year warranty on a new lens. I suppose you are not covered by purchasing via Hong Kong?
12-07-2011, 11:38 PM   #13
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I just phoned EBay and the guy has opened up a dispute case through Paypal apparently the buyer is protected for 45 days there abouts after purchasing an item. He said I'm entitled to a refund and wants me to fill out the clain form and they will take the matter up for me.
I just don't like the idea of me having to do the running around to get the lens fixed.
Just saw a Pentax 16-45mm lens for sale I might grab that, it can't be any worse than the Tamaron.
12-08-2011, 07:42 AM   #14
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The Tamron is a beautiful lens (better than the 16-45) so get it fixed or replaced. I have one I'm going to be selling soon if you get your money back.
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