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06-27-2012, 07:21 AM   #1
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Tamron 17-50 Focus Behavior...

I've had my Tamron 17-50 for about 4 years now on both a K10d and K5. Up until a couple of weeks ago it had been perfect. It was sharp and focused on what I expected it to. All of a sudden a couple of weeks ago, everything became soft with it. I don't mean extremely soft, but just enough.

I've trying to figure out exactly what is wrong or what the symptoms are, but it is hard to narrow it down. On landscape shots everything is just soft (infinity focus, any aperture). Testing on close up shots (minimum focus distance) it seems to be front focusing relatively badly. I've played around with different focal points to verify that is occurring.

All other lenses focus fine, and I have not focus adjusted any lens. I've tried focus adjusting this specific lens and there is a bit of an improvement but just a bit. At wide open apertures the focal point is now at the furthest point in the DOF. It might be ok, but I am still puzzled at what could have occurred to make this occur. The lens was always so sharp for me, at least as sharp as a zoom could be. Now, I think it may be worse than my kit lens.

06-27-2012, 07:28 AM   #2
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Have you tried to focus manualy?
06-27-2012, 07:34 AM   #3
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You need to determine whether it is just a focusing issue,
or whether some other effect is in play (e.g. decentering after a shock).

I would suggest using contrast-detect focusing in live view.
If the photos then look sharp, it's a focusing issue.
Otherwise, there's a more serious problem.

If the lens has the 6 year Tamron warranty,
you should be able to get it fixed.
06-27-2012, 07:56 AM   #4
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Thanks for the suggestion... I'll check that out. That's the type of information I was looking for... I'll have to check on the warranty, too.

06-27-2012, 09:37 AM   #5
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Anothing thing to try is turning off SR. My old K100D intermittently had this issue and some of the photos came out soft.
07-25-2012, 11:41 PM   #6
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I have a similar issue with mine on my K-30. Front focus heavily, differing amounts and different zoom levels and much less at extreme closeups near minimum focal distance. My K20D was able to have accurate focus with in-cam adjustments, but only for 17mm or 50mm they needed different amounts. The k-30 with full adjustment is out still at all zooms and focus distances.

I've sent mine into our local tamron service dept last week, who told me today they were unable to fix it with shims or any standard adjustment and would have to speak with Tamron agents overseas. Oh and mine was 2nd hand from on here and I have no warrenty details

I think I would also like to try the contrast auto-focus tests, to see if it is the phase vs physical lens issue.
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