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Tokina 17mm F3.5 AT-X 17 AF - Fungus?

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Neildlr View Drop Down
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Post Options Post Options   Quote Neildlr Quote  Post ReplyReply Direct Link To This Post Topic: Tokina 17mm F3.5 AT-X 17 AF - Fungus?
    Posted: 06 March 2023 at 16:56
Hi everyone. I need some help please.

I bought this lens today and while it is in otherwise perfect condition, I can't tell if these marks on the very final element at the back are just some manufacturing scratches on the glass or if it is fungus?

It doesn't seem to affect the image quality.

Photo taken with a 70mm Macro, full res link below.

https://ibb.co/jrpDYNG



Edited by Neildlr - 06 March 2023 at 17:11
 



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Neildlr View Drop Down
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Post Options Post Options   Quote Neildlr Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2023 at 08:25
My apologies, I just realised that this post should probably be in the A-Mount Lens sub forum.

Can a moderator please move it?
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Snegren View Drop Down
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Post Options Post Options   Quote Snegren Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2023 at 08:59
Looks like fungus to me. Lens element easily removes as I see a slotted holding ring. Perhaps you can clean, but if you can return with refund you avoid disappointment when you can't clean. If you leave it it may grow until you cannot use the lens anymore.
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japp View Drop Down
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Post Options Post Options   Quote japp Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2023 at 10:10
i don't know if it actually is fungus, normaly fungus leaves some lines but this looks kind of like a bit of dust or something. and i would agree with Snegren's advice.
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Neildlr View Drop Down
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Post Options Post Options   Quote Neildlr Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2023 at 12:47
I tried to clean it with a lens pen first, then tried a very lightly damp cloth that I carefully pushed with a plastic toothpick. None of that worked.

Then I carefully felt it using the toothpick and it actually feels like the glass has been sanded or scuffed?
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Snegren View Drop Down
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Post Options Post Options   Quote Snegren Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2023 at 13:43
Sanded or scuffed would not make sense. Fungus can form acids that etch the glass. But, if you feel the glass is cleaned and the lens works well, problem solved isn't it.
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Neildlr View Drop Down
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Post Options Post Options   Quote Neildlr Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2023 at 13:52
I guess so. Its the first time I've ever seen this on a vintage lens (in the ones I've physically come across) so its just a bit odd.

I'll see if it gets larger or anything and then i guess we'll know.

I have seen reports that fungus can leave marks on the coatings even after being cleaned so maybe this lens has had fungus in the past?
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Post Options Post Options   Quote Snegren Quote  Post ReplyReply Direct Link To This Post Posted: 07 March 2023 at 20:40
Originally posted by Neildlr Neildlr wrote:

I guess so. Its the first time I've ever seen this on a vintage lens (in the ones I've physically come across) so its just a bit odd.

I'll see if it gets larger or anything and then i guess we'll know.

I have seen reports that fungus can leave marks on the coatings even after being cleaned so maybe this lens has had fungus in the past?

Your guess is as good as mine
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skm.sa100 View Drop Down
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Post Options Post Options   Quote skm.sa100 Quote  Post ReplyReply Direct Link To This Post Posted: 09 March 2023 at 09:11
Instead of illuminating the lens from the front, it's better to hold up a flashlight thru the back of the lens and take a picture with the exact element in focus.
Fungus leaves telltale lines and dots and when you flash a light thru the back of the lens, it can show up as tendrils.
It's quite normal that the pictures with the lens might be fine. The fungus could stay that way for years without growing, if it is fungus.
But since it's a recent purchase, you might want to return it just to make sure you didn't pay market price for what could turn out to be a dud.
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Sashi
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Post Options Post Options   Quote Neildlr Quote  Post ReplyReply Direct Link To This Post Posted: 09 March 2023 at 13:21
So I just had a good look as suggested, shining a large LED light through the front element and looking at the rear element. Still looks pretty much the same. No lines or tendrils. A few pieces of dust.

I think I got it for a pretty good price (about half what I see it go for on ebay) and in my country it is fairly uncommon to find good A-Mount lenses, especially primes. I also got this with a Minolta 24mm 2.8 which is in perfect condition, except for the scratches on the outside of the hood.

So, as long as these marks don't get any worse I'm very happy with the lens.
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