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Author Topic: visible grain on lens preventing autofocus  (Read 421 times)

mfrohman

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visible grain on lens preventing autofocus
« on: September 25, 2018, 09:17:07 PM »

Hi all,

I just purchased a Pentax k-1 with a PENTAX-D FA 28-105mm f/3.5-5.6 ED DC WR Lens. I'm noticing a really even fine grain visible through the viewfinder across the frame and it is not autofocusing correctly. I've tried another lens and don't have this problem with it so it seems to be the lens. The strange thing is the grain doesn't seem to show up on the photos.

any ideas? defective lens? or defective user?
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mlt1

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Re: visible grain on lens preventing autofocus
« Reply #1 on: September 26, 2018, 02:54:53 PM »

Try cleaning contacts on the lens, otw try another copy of the lens if possible.  This is a very sharp quick and accurate lens for the price.
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mfrohman

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Re: visible grain on lens preventing autofocus
« Reply #2 on: September 26, 2018, 05:14:54 PM »

thanks for the advice, just ordered some contact cleaner. Will report back.
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mfrohman

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Re: visible grain on lens preventing autofocus
« Reply #3 on: October 24, 2018, 08:55:17 PM »

I tried cleaning the lens and it didn't seem to help. Still won't lock autofocus and still seeing this fine grain through the viewfinder, even though it doesn't show on photos. Manual focus works fine. Any other ideas?
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Two23

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Re: visible grain on lens preventing autofocus
« Reply #4 on: October 25, 2018, 09:56:08 AM »

Grain  is most likely from the ground glass focus screen.


Kent in SD
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Telecaster

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Re: visible grain on lens preventing autofocus
« Reply #5 on: October 25, 2018, 03:34:37 PM »

Yep, the screen likely has a graininess to it that shows up at smaller apertures. Wonder if the lens is somehow operating in stop-down mode? I'd try to get a replacement copy of it.

-Dave-
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