Bigma internal focus adjustment.

Started Mar 28, 2005 | Discussions thread
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Roy
Roy
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Bigma internal focus adjustment.
Mar 28, 2005

After seeing Drips post on Sigma adjusting his Bigma I decided to try to do the same to mine. To whoever is interested that their copy isn't as sharp as Drips this might be the answer. The very rear element is adjustable. You remove the rear black plastic cover between or around the element and the contacts (three screws). Pull the cover off gently. Then you are able to turn that element tightening or loosening maybe 1/4 turn or more whatever it takes. In my case loosening a 1/4 turn made mine almost as sharp as my 120-300 (really close almost inperceptable, I used this lens to tell when I had it) but definitely a huge difference in sharpness. Yours might be 1/8 either way but if it is close I wouldn't mess with it. I just suspect this is all Sigma does probably hooked to a machine to test it. When you think you have it replace the cover which holds it from turning and that's it. I did the 1/4 turn unscrew saw how sharp it was and that's it, I didn't want to get buggy. Anyway do it at your own risk, I can only say it made a big imrpvement at ALL focal lengths on my Bigma which only is amplified by the extender and makes my Bigma much sharper than my 80-400 OS now.

Good Luck
Roy

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