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09-16-2010, 02:05 AM   #1
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Tamron 17-50mm Issue: Overexposure

Hi,
I just got my Tamron 17-50mm/2.8 back from a warranty repair for focusing issues. These are the technician comment on the receipt:

TESTED ON PROJECTION TOOL
ALL IN STANDARD ON ALL AREAS OF IMAGE
TESTED ON ALIGNMENT FOR G3 OPTIC - IN STANDARD
TESTED FOR FOCUS FOUND TO BE BACK FOCUSING
REMOVED AN REPLACED CIRCUITS AS NECESSARY
TO ADJUST TO CORRECT
PART: CIRCUIT E1 AP16-P90-00

However it seems there is a new problem now: Basically all photos with f > 2.8 are overexposed. The smaller the aperture the worse it gets. The issue is existent in all camera modes and settings. I have uploaded a few examples at different apertures here:

Tamron 16092010 - d3zzzz's Photos

Earlier today I have mailed Maxwell International Australia to get the technician to provide some feedback. But I thought someone here might have some valuable advice...

Thanks,
Chris



09-16-2010, 02:23 AM   #2
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Looks like the aperture didn't stop down at all as the DOF stays the same. Perhaps the rear lever was bent outward so it stuck with the camera? You might flip it with finger and see if the aperture blades stop down.
09-16-2010, 03:12 AM   #3
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Thanks for yiyr quick response, wlachan.

Ich just cheched the lever. It sits at the wrong end (Wide open apeture). If you flick it the blades stop down. Does that mean they assembled the spring that holds the lever incorrectly?
Attached Images
 
09-16-2010, 03:56 AM   #4
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Indeed the lever is at the wrong end. Does it move at all? Is it still spring loaded? If it moves but not spring loaded, it could be that the technician forgot to hook it back. If it is spring loaded, I cannot see what could cause that. However, you should be able to remove the rear black cover and see what happened. There is a good chance you might be able to correct it.


Last edited by wlachan; 09-16-2010 at 04:03 AM.
09-16-2010, 04:11 AM   #5
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Yes, the lever does move and it's spring loaded. You reckon I should remove the back cover? Never done that before. The lens is still under warranty. I might just send it back. But that means it will be gone for couple of weeks ... again.
09-16-2010, 04:15 AM   #6
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That's a tough call. Maybe you can peep inside with a flashlight by retracting the rear element (zooming) and see how the lever works?
09-16-2010, 04:33 AM   #7
Ash
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Sticky aperture lever?!? Check it by dismounting the lens after the overexposure problem becomes evident on the camera, and having a look at the aperture blades with your eye through the lens. Seeing an open lens means the lever is getting stuck and doesn't spring back to stop down the lens when needed.

Sorry mate, that's something that should be left to the repairers to do under warranty, but I didn't think any other Tamrons (other than the 70-200) was susceptible to this problem - let alone induced by a repair...

Hope you work things out in good time. A good 17-50 is a gem.
09-16-2010, 04:42 AM   #8
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Thanks for your advice, guys! Really appreciate it! I just sent another email to the technician. Seems obvious he made a mistake when puttting the lens back together. So I guess I'll send it back to get it fixed.

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