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02-04-2014, 02:39 PM   #1
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Name this lens defect!

I have an old Focal (K-Mart) 80-200mm f/3.5 lens. The front element/group has a ragged, transparent, metallic band on the rim. I know it's not fungus. Are a couple of elements coming apart?

02-04-2014, 02:51 PM   #2
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Can you post a pic??
02-04-2014, 03:05 PM   #3
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Hard to say without a pic, could it be dried cleaning fluid or something like that? That stuff is quite hard to get off sometimes.
02-04-2014, 06:39 PM   #4
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Whatever it is, I shall name it "Tighelander" - congratulations!

02-05-2014, 12:25 AM   #5
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In this photo the defect is reflecting the light. At other angles, it's transparent. It's on the inside of the element/group. It's around the rim of the glass like a ragged fringe.
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02-05-2014, 04:00 AM   #6
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Possibly oil from separating helicoid grease that is creeping on to the elements ? or maybe schneideritis - where the black paint around the edge of an element degrades and lets light in through the edge, but that is usually more whitish spots?
02-05-2014, 04:08 AM   #7
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It would to have a lens diagram, is that a kitted group in front or just a single element?

You should be able to unscrew the retention ring around the front element/group and take it out for cleaning.
02-05-2014, 10:52 AM   #8
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I had a 400mm lens with a very similar fault see here
Tele-Astranar 400mm F6.3 Lens Reviews - Miscellaneous Lenses - Pentax Lens Review Database
pic in first review

The good news is that the effect on the pics wwas negligible.
I couldn't decide whether this was incipient separation of the doublet, or leakage/condensation of volatiles from the thread locking chemical (or st else..?). In any case I decided that any attempt to separate the doublet was more likely to cause damage than a fix.

02-05-2014, 01:50 PM - 1 Like   #9
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Based on the picture I would say it looks like cleaning fluid that seeped in from the top of the front element and never dried. If it did dry then it left some goop behind. Seeing that it is on the very outer edge of the glass I wouldn't worry about it. Even if it were haze in the center then the worst that happens is a loss of contrast. You would probably notice it in that case when shooting uniformly lit flat subjects of one color. In real life situations with varying colors and contrasts you probably won't notice a thing. Since it's off the edges I think you won't notice anything anyways.
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