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07-15-2016, 12:24 AM   #1
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Manual focus lens issue

Hi forum,

I am in need of expertise from the wider community. I am hoping someone cant point me in the right direction of what the issue might be.

I have a 100mm f2.8 manual focus lens that doesn't focus correctly. I'm all over little things like the focus grouping not replaced in the right position after being opened etc.

However the lens I have is currently focusing on what seems to be two points. One far off and one closer to the camera.

At infinity all objects in the distance are blurry and when adjusting the focus closer to the camera slightly the objects at infinity become sharp, however the image at a mid distance of approx 10m (30ft) are fairly soft and the image at a closer distance of approx 2-3m (6-9ft) are sharper again. I also are unable to sharpen up the mid distance image by adjusting focus although the lens functions correctly mechanically.

Because of work I will do a more comprehensive test of the focus with a tripod and take video to post before I open the lens up after the weekend but any provided would be great.
Thanks in advance.

07-15-2016, 03:41 AM   #2
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QuoteOriginally posted by Louicio Quote
Hi forum,

I am in need of expertise from the wider community. I am hoping someone cant point me in the right direction of what the issue might be.

I have a 100mm f2.8 manual focus lens that doesn't focus correctly. I'm all over little things like the focus grouping not replaced in the right position after being opened etc.

However the lens I have is currently focusing on what seems to be two points. One far off and one closer to the camera.

At infinity all objects in the distance are blurry and when adjusting the focus closer to the camera slightly the objects at infinity become sharp, however the image at a mid distance of approx 10m (30ft) are fairly soft and the image at a closer distance of approx 2-3m (6-9ft) are sharper again. I also are unable to sharpen up the mid distance image by adjusting focus although the lens functions correctly mechanically.

Because of work I will do a more comprehensive test of the focus with a tripod and take video to post before I open the lens up after the weekend but any provided would be great.
Thanks in advance.
I have not experienced these issues that you are experiencing. I do know someone who did have these same problems. It seemed that one or two of the optics slipped loose from the adhesives. He did the calibrations and after that he would have great focusing, but shortly the problem returned. The last time I spoke with him he ended up donating the lens to his favorite charity because repairs were much more expensive than what the lens was worth. I do not know if this helps, I hope it does, so good luck with that.

Regards,

Antonio
07-15-2016, 04:00 AM   #3
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Which lens is it?
07-15-2016, 07:10 AM   #4
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Is there anything loose (shake the lens does it rattle)? On the occasions I've had funny focus issues it's been due to a loose element.

08-01-2016, 10:14 AM   #5
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Thanks everyone who replied. Just thought I'd follow up with the outcome. Pulled the lens apart (its a Nikon E series 100mm f2.8) and turns out a small metal ring used to space and hold one of the glass elements was inserted backwards allowing it to move and the element was crooked. Replaced correctly and cleaned the glass and works like a treat now! winning!
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