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05-10-2013, 06:33 PM   #1
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Help, focus on 70-300 not working

Hello. As the title states I am having focusing issues with a Tamron 70-300mm I picked up from the PO Box today.
The lens is going on my relatively new K30 (also my first DSLR). Past about 150mm, auto focus doesn't lock on. The camera just keeps attempting to focus with no lock, even though the lens travels through what appears to be a focused point.
Manual focus works all the way out to 300mm.

Any ideas?

05-10-2013, 09:04 PM   #2
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Does the image seem dark when viewed through he viewfinder? If so, the aperture blades may be stuck and the camera is having a hard time focusing due to the limited light.
Happened to me with a 70-300 sigma.
05-11-2013, 02:55 AM   #3
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If I remember correctly the Tamron is not constant aperture.

Could it be that in the conditions you checked it in the smaller f-stop at the longer end just didn't allow enough light through for focus lock?
05-11-2013, 01:02 PM   #4
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Original Poster
The image appears normal through the viewfinder. I can easily see the image focus as the camera hunts to lock a focus point.
I was unable to lock on to anything at 5.6. It was cloudy outside but at 2 in the afternoon, not terribly dark.

When fully zoomed, the camera allows me to select 4 for an aperture setting even though the lens should max out at 5.6 at 300mm. Perhaps my problem is connected somehow to this?

05-13-2013, 04:00 PM   #5
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I checked today and the focusing works with live view. Still, no dice with the viewfinder.

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