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08-17-2013, 01:45 PM   #1
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Weird swirl pattern inside lens

Can anyone tell me what this swirl pattern is?

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08-17-2013, 02:01 PM   #2
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Kinds looks a lot like a finger print. Cant wipe it off? Could be some oil residue
08-17-2013, 02:25 PM   #3
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It looks a bit like it could be the dreaded fungus.
08-17-2013, 02:27 PM   #4
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Looks like you are showing off your nifty fifty

08-17-2013, 02:43 PM   #5
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I had a lens with what looks like the same condition as your lens:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/219686-swirly-...r-element.html

I think it was a case of eroded lens coatings:

http://www.techarp.com/showarticle.aspx?artno=194&pgno=6

I don't think much can be done about it, but it didn't really affect the IQ of the lens. The only thing was that it made flare even worse, but a hood eliminated it completely.
08-17-2013, 03:00 PM   #6
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It is definitely on the inside of the lens, and it has no effect on IQ. I think I'll go with the suggestion of lens coating coming off.
08-22-2013, 03:29 PM   #7
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QuoteOriginally posted by djam Quote
It is definitely on the inside of the lens, and it has no effect on IQ. I think I'll go with the suggestion of lens coating coming off.
I have a very similar looking thing in my 100mm f4 macro, though not as visible, and I am told by an experienced Pentax lens repairer that it is element separation, or particularly failure of the compound used to secure two elements of a group together. It's not an adhesive as such, apparently a balsam based material.

It is repairable, (at a cost that may make it not worth while), but means separating the two elements using heat, and then re-assembling, after cleaning in a really clean environment.

David
08-22-2013, 03:59 PM   #8
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QuoteOriginally posted by djam Quote
It is definitely on the inside of the lens, and it has no effect on IQ. I think I'll go with the suggestion of lens coating coming off.
Yeah it does kinda look like degradation of the coating. Had a similar issue with a Kiron lens before...I don't remember it affecting IQ much, the thing to look for though is in the bright bokeh highlights (eg. let's say christmas lights in the BG). I remember the exact same pattern from the lens coating would replicate in every single one of the highlights.

08-22-2013, 04:42 PM - 1 Like   #9
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Looks like fungus to me.
08-23-2013, 12:36 PM   #10
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The cement used is Canadian Balsam. Also used to cement binocular lenses together, which is why I know about it, I repaired them in the military. It's applied and removed by heat, I can't remember how hot but above car trunk in Texas temp and below making pancakes...anyway it's not cheap, mainly because it has to be done in a very clean environment, almost a white room, and the lenses have to be well centered with each other after finishing, which took me 4 tries my first time. And specialized equipment is required to do the alignment. Fortunately I didn't have to do a 3 lens eyelens element, just a 2 lens objective lens.
08-23-2013, 12:51 PM   #11
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Thanks Paleo. I haven't noticed any trouble with image quality, but I did notice some flare when I tested for that, but as long as its not fungus and the images are sharp I am not going to worry about it.
08-23-2013, 01:00 PM   #12
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I'll throw in another vote for coating failure, and you're right to not worry about it. It takes a lot more to ruin a lens than most people realize. Take a look at this thread:

https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/231454-guess-lens.html

Or this one:

https://www.pentaxforums.com/forums/lens-clubs/40521-dead-lens-club.html
08-23-2013, 01:50 PM   #13
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That is great info. Thanks for sharing.
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