scratch / fungus ?

Adalbert · Post by **Adalbert** » Mon Nov 12, 2018 3:25 pm

Hello everybody,
Does anybody know if this fungus inside of the lens (rear side) can affect the quality of the image?

1x

4x

Thank you in advance.
BR, ADi

JohnyM · Post by **JohnyM** » Mon Nov 12, 2018 3:41 pm

Doesnt look like fungus. Can you magnify more?
Shouldnt affect IQ in any way than slight lost of conrast locally.

ray_parkhurst · Post by **ray_parkhurst** » Mon Nov 12, 2018 5:07 pm

I agree with JohnyM, doesn't look like fungus, but it's not likely to affect the image.

Adalbert · Post by **Adalbert** » Tue Nov 13, 2018 2:24 am

Hello Johny, hello Ray,
It is not easy to take the photographs of that because it is inside of the lens not on its surface.
But I will try :-)
BR, ADi

ray_parkhurst · Post by **ray_parkhurst** » Tue Nov 13, 2018 7:10 am

Here's a pic of lens fungus between elements that I took at ~6x. Shows multiple species.

Adalbert · Post by **Adalbert** » Tue Nov 13, 2018 7:41 am

Hi Ray,
Many thanks! It looks like a snowflake :-)
I can see a small grain of dust inside my lens, it is not on its surface.
BTW, the second photographs in following thread has been taken by the usage of this lens:
https://www.photomacrography.net/forum/ ... highlight=
BR, ADi

Adalbert · Post by **Adalbert** » Tue Nov 13, 2018 1:37 pm

Hi,
And a little bit more magnified:

BR, ADi

ray_parkhurst · Post by **ray_parkhurst** » Tue Nov 13, 2018 5:04 pm

Looks inorganic to me. If it's between the lens elements, then it may be a manufacturing defect. For sure, it's so small that you probably won't see any impact on IQ.

Adalbert · Post by **Adalbert** » Wed Nov 14, 2018 9:06 am

Hi Ray,
It is 1mm below the surface, inside of the lens

BR, ADi

ray_parkhurst · Post by **ray_parkhurst** » Wed Nov 14, 2018 9:30 am

Adalbert wrote:Hi Ray,
It is 1mm below the surface, inside of the lens
BR, ADi

If you are concerned about the small potential degradation in contrast due to light diffusion from the defect, you can put a small "dab" of black paint onto the lens element to cover the area. This will slightly reduce the maximum aperture (for instance, from f4.00 to f4.01) but will block light from hitting the defect and diffusing to unwanted areas. This is the same type of trick folks use for scratches, ie marking the scratch with a sharpie so that light does not pass through it.

ChrisR · Post by **ChrisR** » Wed Nov 14, 2018 3:26 pm

If you turned your yellow arrow into black paper, and extended it to cover the defect, you might see a difference.
I would bet not much, though!

Adalbert · Post by **Adalbert** » Thu Nov 15, 2018 8:59 am

Hi Ray, hi Chris,
OK, I’ll check it.
BR, ADi

Pitufo · Post by **Pitufo** » Thu Nov 15, 2018 11:24 am

Speaking of fungal growth, this is part of a microscope that landed in front of me today. It had been used at sea (!). Most of the optical surfaces were like this. Surprisingly, it seemed to clean up well (IPA wasn't that good but Zeiss Lens wipes worked much better).

Apologies for the image quality. An over-sharpened mobile phone crop..

Scarodactyl · Post by **Scarodactyl** » Fri Nov 16, 2018 6:46 pm

Yeah, it's amazing but every now and then you get lucky and it just wipes off. I guess not every species produces etchants, maybe seafaring fungus have different priorities.

Adalbert · Post by **Adalbert** » Fri Nov 30, 2018 8:40 am

Hello everybody,
It is a small scratch, which has been detected by the test with a toothpick :-)
Should I try to "fill" it with UV adhesive or synthetic resin ?
BR, ADi