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01-18-2018, 06:01 PM   #1
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Join Date: Aug 2011
Location: Michigan
Posts: 103
A new kind of lens oddity?

I just received an FA 20-35 that I bought, and I noticed something right away that I have not seen before or heard about as a type of issue. There seems to be some glue or sealant around the inside of the front element that is not evenly applied. This can be seen by looking from the front, but mainly by looking at the front element from an angle. There are also a few spots of the substance that are not connected to the bead around the edge. See pictures below. Has anyone seen this kind of thing before? I am not sure that it is even a problem. I have not taken many test shots yet. I am mainly wondering if it is indicative of some larger issue.

Thanks for any insights.

01-18-2018, 06:58 PM   #2

Join Date: Jan 2011
Location: New York
Posts: 4,517
It looks black in the photos. Maybe it's some sloppily applied lens blackening? The outside circumferential edge of elements is sometimes painted black; it improves contrast because it stops reflections from bouncing around.

In your last photo, looking along the 1:00 to 3:00 positions, the markings look mirrored. There are 4 matching pairs of marks. I can't tell if the marks are on 2 separate pieces of glass, or on 1 piece of glass and reflected off another piece.
01-18-2018, 07:28 PM   #3
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Join Date: Aug 2011
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Original Poster
The duplicated marks you see in the head-on shot are reflections. In that picture I believe that the inner most marks are the direct view and the outer marks are their reflections.

I guess it could be blackening. Regardless of what exactly it is, it seems to beg the question about whether the lens is been worked-on in the past. The lens has some wear, but I don't see any direct evidence that it has been disassembled. I have also wondered if the glue/sealant/blackening could have worked itself out of where it is supposed to be due to temperature extremes?
01-19-2018, 05:18 AM   #4
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I'm not sure what that is, but I did check my copy of that lens and I didn't see anything similar on it.


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