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Old Apr 11, 2005, 9:10 AM   #1
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The performance of myTamron 28-75 Di lenshas me worried. From time to time I've had images that seemed soft even though I'd taken care to use Center Point only focusing, locked on target and close inspection ruled out camera motion. The lenswassent to Tamron Service Center for correction of a front focus problem and I asked them to calibrate the lens before returning it.

I decided to do a controlled test so the Canon 10D was mounted on a tripod, set to ISO100 and f/6.3. Lenses were set to 50mm and were focused, using Center Point only, to a distant tree studded hill about 2 miles away. Three lenses were used, the Tamron 28-75 Di, Tokina 24-200 and a Canon 50mm f/1.8.

The tests results showed the Tamron was much softer than the other two lenses.

After printing and inspecting the results the only thing I could think of to try was blow out the camera's interior in the faint hope that dust may some how be causing a problem with the focus sensor and run a pencil eraser over the Tamron's lens contacts.

I repeated the test the next day and now the Tamron was nearly as sharp and the Canon f/1.8. It's hard for me to believe what I did corrected the problem.

Any ideas?

Glenn














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