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11-02-2010, 08:54 PM   #1
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Uneven coating discoloration deep in an old lens...

Bought a Kiron 70-210mm f/4 from that auction site, and true to the pictures the front and rear elements are pristine, however one element deep in the lens (probably the element in front of the aperture blades) has iridescent spots/discoloration which wasn't visible in any auction photos. I can only see it by shining a desk lamp or flashlight directly down into the lens at the proper angle. Perhaps there was some moisture in the lens at one point? I'm not sure, haven't seen anything like it in other old lenses...

Anyone have any ideas how much of a priority I should make it to try to get that element cleaned up, how feasible it is, how much it might cost, and where I might send it to?

11-02-2010, 09:17 PM   #2
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I don't know how to solve it, but I would first take some photos. If you don't see the effect of the discolouring, I would not worry.

Just my 2 cents.
11-03-2010, 10:28 AM   #3
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I'd suggest you try the lens under different conditions to see if there's any problems with the IQ. Also Kirons are known have to have oily aperture blades which is caused by the degredation of the grease in the focus helicoid. Maybe some of that oil is on the element?
11-03-2010, 12:36 PM   #4
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QuoteOriginally posted by ovim Quote
I'd suggest you try the lens under different conditions to see if there's any problems with the IQ. Also Kirons are known have to have oily aperture blades which is caused by the degredation of the grease in the focus helicoid. Maybe some of that oil is on the element?
Yes when I get the chance to take it out, I plan to see what the effects are... I figure that if it is isolated to one element like I think it is, it might not be immediately evident or evident under all conditions because the effects would primarily have to do with the reflectivity/transmissiveness for that one element, which would affect efficiency and/or flare.

There are some minor marks on the aperture blades that make it appear like something happened to them at one point, but no oil that I can see, and they are snappy. I'll try to take some pictures as well (a good way to make use of my new tripod/ballhead).

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