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What are those dendrites on my lens

 
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zzffnn



Joined: 22 May 2014
Posts: 1661
Location: Texas USA

PostPosted: Fri Jan 26, 2018 5:10 pm    Post subject: What are those dendrites on my lens Reply with quote

I found these tiny separated dendrites / trichomes on top surface of top lens of my Schneider Componon S 50mm F/2.8 (inner surface of the top lens looked perfect, when I removed the lens and examined/cleaned both surfaces). Please kindly tell me what they may be.



They are not cracks. They kinda look like very superficial scratches, but with dendrite patterns. Xylene, 91% alcohol or hydrogen peroxide wipes did nothing to them.

Could those be mold damages, even though mold has been removed?

The lens looks almost perfect, when I examined it from the other side, against oblique light. That was likely why I did not find those dendrites, when I received the lens from Keh Camera last year. Keh did not mention those dendrites, when they sold me the lens. Images produced by the lens look good.

The dendrites don't look that obvious in person, the poorly focused photo makes them look a bit worse.

I only find issues, when I want to sell optics (I usually don't see issues, or I don't examine them carefully enough, when I receive them as buyer).
Crying or Very sad

I can upload a better image, if necessary, in a few days.

Thank you very much!

I am selling this lens by the way, because I prefer the convenient and fast automatic focus bracketing of my Olympus camera, with Raynox 150/250 over auto m4/3 lenses. This lens has been staying in a dry box since I received it.

Please feel free to message me for buying or trading it. I can take an self-corrected infinity 4x (e.g., Nikon BE Plan) or 10x objective as trade. Plus or minus money from either side.


Last edited by zzffnn on Fri Feb 09, 2018 2:28 pm; edited 2 times in total
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ray_parkhurst



Joined: 20 Nov 2010
Posts: 1217
Location: Santa Clara, CA, USA

PostPosted: Fri Jan 26, 2018 7:48 pm    Post subject: Reply with quote

Hard to tell from your photos if these are lens fungus. Need higher mag images.

Surface fungus can usually be cleaned with water. I have successfully cleaned lenses with heavy fungal growth simply by breathing on the lens surface to moisten the fungus, allowing it to soak for a minute or so (with more breaths if needed), then cleaning with a lens cleaning solution. The fungus comes off fairly easily, but if the colonies have damaged the lens coatings or etched the glass surface, you will still see the damage.

edited to add:

Here's are some images I made of some fungal colonies on a lens. There are a few different species present:



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zzffnn



Joined: 22 May 2014
Posts: 1661
Location: Texas USA

PostPosted: Fri Jan 26, 2018 8:52 pm    Post subject: Reply with quote

Thank you very much, Ray.

Fungus etching is what I fear for.

I will image them under microscope.

The things on my lens are not original fungus organisms for sure. As they don't go away, after many firm wipes of H2O2, alcohol or xylene.

Their shapes don't look like any of yours, though there are many different types of fungus for sure.

My shapes look like individual (separated) plant trichromes, like this: http://www.microlabgallery.com/gallery/Plant%20Hair945-12%202a.aspx
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phil m



Joined: 10 Aug 2014
Posts: 156

PostPosted: Mon Jan 29, 2018 6:44 am    Post subject: Reply with quote

If you could provide a more magnified image, Fan, it would be helpful.

I have seen some interl-lens structures similar to what you describe; something like plant hairs in the cement of some older doublets. The manufacturers were probably using newer cement technology at the time; just after balsam began to be replaced.

What I observed were definitely not fungus but had a whitish more crystalline structure, possibly due to uneven drying or curing.

The contamination resulted in a contrast reduction and seemed to be unrepairable, using any solvents available to me at the time. I have separated and re-cemented balsam fused lenses before.

I have heard that heat , around the temp. of boiling water can redissolve some of the synthetic cements and reset them.

Obviously, keeping the elements aligned correctly during any liquifying procedure is paramount. I have done that with small doublets successfully by placing them in a pill bottle between firm, sculpted pads of cork, using the convex plastic cap liner for some compression, then immersing the whole thing in 200 degree water for a while. I suppose a similar system could be arranged for large lenses.
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zzffnn



Joined: 22 May 2014
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Location: Texas USA

PostPosted: Mon Jan 29, 2018 5:17 pm    Post subject: Reply with quote

Theses photos were taken afocally with a B&L Stereozoom 7 scope. Sorry for the low contrast; I found them difficult to photograph without serious lighting tweaks and stacking. Those dendrites are mostly on lens periphery and not in one focus plane.

On sensor magnification is about 2x to 6x. Camera sensor is micro four thirds.

front lens view at around 2x (again those dendrites are on the front surface of front lens; the pink/purple light patch is reflection and the blue markings were made by me for location marking. When I reduced reflection by diffusion, the dendrites became harder to see):


front lens view zoomed to 6x and heavily cropped:


Back lens view at around 2x:


The blue markings were made by me.


Last edited by zzffnn on Mon Jan 29, 2018 5:26 pm; edited 3 times in total
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zzffnn



Joined: 22 May 2014
Posts: 1661
Location: Texas USA

PostPosted: Mon Jan 29, 2018 5:22 pm    Post subject: Reply with quote

Thank you very much, Phil.

Wouldn't cement residues reside in between lens elements, instead of on top of top lens top surface? I am pretty sure my "dendrites" are located on top lens top surface, because I have removed the top lens to examine its top and bottom surfaces.
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phil m



Joined: 10 Aug 2014
Posts: 156

PostPosted: Fri Feb 02, 2018 7:35 am    Post subject: Reply with quote

Yes. they would be inter-lens.
I don't suppose you would know, what kind of glass is being affected, would you? and the lens is quite old isn't it?
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zzffnn



Joined: 22 May 2014
Posts: 1661
Location: Texas USA

PostPosted: Fri Feb 02, 2018 8:00 am    Post subject: Reply with quote

Thanks, Phil. I don't know.

The entire lens looks quite good in appearance, though its original manufacturing date may be some 60 years ago. I don't know for sure.

I know the shape and diameter of the affected top lens and can draw it, if you need. Don't know how to call it or what exact kind.

I suspect damage left by fungus. Not sure.

Imagery from the lens looks good actually. There are about 12 of those dendrites, on the periphery (some spots in the first image were dust particles). I didn't even see them until last week.

I am keeping this lens. It works pretty well reversed for 1x-2x on sensor.
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zzffnn



Joined: 22 May 2014
Posts: 1661
Location: Texas USA

PostPosted: Sat Feb 03, 2018 12:28 pm    Post subject: Reply with quote

Any other advice or comments? Thank you.
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ray_parkhurst



Joined: 20 Nov 2010
Posts: 1217
Location: Santa Clara, CA, USA

PostPosted: Sat Feb 03, 2018 4:18 pm    Post subject: Reply with quote

zzffnn wrote:
Any other advice or comments? Thank you.


If the fungus cannot be cleaned, you should neutralize it. Leave it out for a few hours in direct sunlight and the UV will kill any active fungus growth, and the lens should be stable for use. Small colonies like this won't usually cause much loss of contrast. I have examples of the same lens with no fungus vs heavy fungus and can't tell much difference in image quality.
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zzffnn



Joined: 22 May 2014
Posts: 1661
Location: Texas USA

PostPosted: Sat Feb 03, 2018 6:34 pm    Post subject: Reply with quote

Thank you, Ray.

I have removed all the fungus, if there was any (I used to a microbiologist by trade). What remains there is not biologically active and is likely tiny damages left by fungus.

Indeed, as I mentioned in my first post, I have not detected any image degradation, surprisingly.
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ray_parkhurst



Joined: 20 Nov 2010
Posts: 1217
Location: Santa Clara, CA, USA

PostPosted: Sat Feb 03, 2018 8:59 pm    Post subject: Reply with quote

Lenses with light fungus, small scratches, etc are among the best values out there. They have almost zero monetary value (try to sell a properly-described lens with fungus on eBay...) yet image quality is really minimally-compromised. Just don't expect to ever recoup your investment, so pay accordingly.
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phil m



Joined: 10 Aug 2014
Posts: 156

PostPosted: Mon Feb 05, 2018 12:11 pm    Post subject: Reply with quote

zzffnn wrote:
Any other advice or comments? Thank you.


The analysis of glass types for chemical durability is a relatively recent study. Data goes back to around 1955 but the broader understanding of the phenomena is quite recent.
Some glasses obviously just naturally fell into a lower hydrolytic class but others would not have or could have been in an environment where natural aging or corrosion of the glass could be accelerated. The damage to your lens , could just be the result of the glass being subject to some corrosion processes.


Last edited by phil m on Mon Feb 05, 2018 5:00 pm; edited 1 time in total
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zzffnn



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PostPosted: Mon Feb 05, 2018 12:52 pm    Post subject: Reply with quote

Thank you very much, Ray and Phil. You are both very kind and helpful.
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