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A 'crack' pattern on bokeh highlight. What is it?
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PostPosted: Tue Aug 30, 2011 2:03 pm    Post subject: A 'crack' pattern on bokeh highlight. What is it? Reply with quote

I just tested my Zuiko lens for it's bokeh highlight and I was surprised to see a 'crack' pattern on the circle.
I have observed the lens and I saw some kind of a layer in the inner rear part of the lens, it's not a bold black line like a hair, and I am sure it's not fungus.
Anybody can identify what it is? Crack? a peel of the coating?





Thanks.


PostPosted: Tue Aug 30, 2011 2:40 pm    Post subject: Reply with quote

IMO it looks nice.
Estetique aside, look for some oil on the blades.


PostPosted: Tue Aug 30, 2011 5:21 pm    Post subject: Reply with quote

I assume, it is something on the glas, not the blades


PostPosted: Tue Aug 30, 2011 6:13 pm    Post subject: Reply with quote

there must be something on the rear lens...


PostPosted: Tue Aug 30, 2011 7:09 pm    Post subject: Reply with quote

NikonD wrote:
there must be something on the rear lens...


+1 ... Something like a small hair ...


Edit: Looking at your signature, i just noticed that the Zuiko lens that you have used for testing is either the 85/2 or the 100/2 ...
After all, now i'm quite sure that this is a rare kind of "fungus pilorum", extremely dangerous for your other lenses ... So, if you don't want it to infect your other lenses, feel free to send it to me (free of charge, of course), so that it can reach my bin of infected lenses Wink ...


PostPosted: Wed Aug 31, 2011 3:35 am    Post subject: Reply with quote

Thanks All for the reply.

@Indiana: it's an old tricks .. doesn't work for me ... hahaha Very Happy

Well, at first I thought it was a hair, but for what I saw it looks something like a kind of glue as if I put a hair-size transparent glue on the lens.
A white transparent hair? Smile


PostPosted: Wed Aug 31, 2011 10:55 am    Post subject: Reply with quote

I would search for a hair near the iris blades - this would be sharp in the bokeh. Probably in a lens group near the iris the glue is broken -separation.


PostPosted: Wed Aug 31, 2011 7:03 pm    Post subject: Reply with quote

nixland wrote:

@Indiana: it's an old tricks .. doesn't work for me ... hahaha Very Happy


Well, at least i have tried Wink ...

Now, what about showing a (possibly macro) picture of the lens wide open, so that we could try to guess what kind of evil is harassing it ?


PostPosted: Thu Sep 01, 2011 4:08 am    Post subject: Reply with quote

indianadinos wrote:
nixland wrote:

@Indiana: it's an old tricks .. doesn't work for me ... hahaha Very Happy


Well, at least i have tried Wink ...

Now, what about showing a (possibly macro) picture of the lens wide open, so that we could try to guess what kind of evil is harassing it ?


I am working at remote area right now till next week and I didn't bring my macro lens or ext. tube.
I'll try to shot the hair-like mark with my macro lens next week (wednesday).


PostPosted: Wed Sep 07, 2011 4:42 pm    Post subject: Reply with quote

Finally got it with my macro lens.
I ask a lens repairmanm he just examined it using flashlight and finally he gave up to identify what it is. Maybe something to do with the coating he said.

Here is the shot. I increase the contrast in PP.



PostPosted: Wed Sep 07, 2011 7:15 pm    Post subject: Reply with quote

Well, i'm far from being an expert, but this doesn't really look like a coating damage to me ...

But i can be wrong ...

Have you tried opening the lens and looking at the surface of the "damaged" element ?


PostPosted: Thu Sep 08, 2011 1:05 am    Post subject: Reply with quote

indianadinos wrote:
Well, i'm far from being an expert, but this doesn't really look like a coating damage to me ...

But i can be wrong ...

Have you tried opening the lens and looking at the surface of the "damaged" element ?


Not yet. I never disassemle a lens before Smile


PostPosted: Thu Sep 08, 2011 6:40 am    Post subject: Reply with quote

Don't hesitate. Most likely there are disassembly instructions available somewhere. Get some precision screwdrivers, a lens wrench an some other tools an you are ready to go Smile


PostPosted: Thu Sep 08, 2011 9:18 am    Post subject: Reply with quote

Not sure if it is good to open the lens:
Seems not to be the hair, from the pictures.
I don´t think it is lens coating, but even it is - one can not simply repair a lens coating. It could be even hard or impossible to get the rest of the coating away.
If it´s a separation (glue or canada balsam error) it could be repaired - but that is not easy. On my DIY directory are some tutorials about such work. My own try was not with a good result up to now.

So if you make primarly images without big bokeh circles, it would be better not to try a repair as a lens repair beginner with a lens that one like.


PostPosted: Thu Sep 08, 2011 2:30 pm    Post subject: Reply with quote

Thank you All for the advices.

I am thinking for selling this lens.