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04-14-2008, 10:59 AM   #1
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Tamron 28-75mm f/2.8 Focusing Issue

I have had this lens now for maybe 3-4 months and I have been noticing that it apears not as sharp as many of the sample I have seen here in the message boards. I have a K10D, generally use program mode for general shooting and center-point focusing, etc. I understand the issues with the cameras in-camera jpeg compression processing, but this seems excessive. My Tamron 18-250mm puts out sharper image than this currently.

What sort of tests can I preform to check for focusing problems (fron-back focus)? Photo examples attached.

Any info will be greatly appreciated.

Thanks

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Last edited by Scout Pro; 04-14-2008 at 11:10 AM. Reason: Wrong image
04-14-2008, 11:17 AM   #2
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i performed several tests on my lens and posted up the results on this forum, except that was about 6 months ago and i deleted them all. But here are a few suggestions: you could take a picture of a ruler. What you would do is place the ruler on a table, stand at one end of the ruler - this is the position that you will test your lens. Then, zoom in close enough so that you see maybe 4-6 inches that spans the length of the frame. Take a picture, at a 45 degree angle to the ruler. Focus on a number, and take a picture. It would help to use a tripod. open the aperture to 2.8. and use the 2 second timer to release the shutter. That way, it would eliminate any human-related shaking. When you pull up the image on a computer, the number you focused on should be sharp, and the numbers away from it should be blurred.

When i did this test, i focused on the '6', and when i pulled up the image on a computer, the number '8' was sharp....
04-15-2008, 10:43 AM   #3
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Original Poster
Ting,

Thanks for the help, I will try this out soon. What did you do about your issue, etc.???
04-15-2008, 07:46 PM   #4
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oh man, that is a long story. in short: i bought the lens over ebay, it is from japan. so i sent it back, then it was returned good as new. had to pay shipping twice. but that was, like a said half a year ago, and the lens is still amazing, no regrets.

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