Stain at the back of a lens. Fungus?

Lemur · Feb 7, 2023

What is it?

Could it be cleaned?

Does it affect the image?

xkaes · Feb 7, 2023

That's an inadequate photo for evaluation. What should we be looking at? We need a closer shot with an arrow or description of what is the "stain".

Huss · Feb 7, 2023

and take the lens cap off so we can also see through it. Show some pics at different angles too

Don_ih · Feb 7, 2023

If it's something you're thinking of buying, look for something else. Never buy a lens with a rear-element problem.

abruzzi · Feb 7, 2023

hard to tell but it kind of looks like separation to me in a crescent from 1 o'clock to 7 o'clock.

Lemur · Feb 7, 2023

Hello, thank you.

It is a lens I want to sell. It is an “inexpensive” Sigma zoom lens, but I could sell it for 100-150 dollars if it is in good condition.

Tomorrow I will try to take more photos without the lens cap.

But I guess the stain is more visible with the lens cap because there is more contrast in that way.

The photo above is with direct sunlight, and we see texture in the stain. But usually, with a softer light, the stain looks more like this:

And I read the word “haze”… could this be haze?

I don’t know if it is separation. I just saw a video and learnt about separation. I can say that I don’t see rainbow-like colors… Tomorrow I will look better.

__Brian · Feb 7, 2023

You would need to disassemble the lens to determine of it is just haze that can be cleaned, or if it is permanent damage to the glass. With this defect, it will only sell for a fraction of what it would normally sell for. Having it professionally cleaned is more than the lens is worth.

Huss · Feb 7, 2023

That looks like lens separation.

Sirius Glass · Feb 7, 2023

Huss said:
That looks like lens separation.

I agree that is is lens separation.

250swb · Feb 9, 2023

Separation, it's dead.

Huss · Feb 9, 2023

I would sell it as a 'special effects' lens. Spin it - this lens is a one of a kind, with unique lens separation that will make your photos stand out.

beemermark · Feb 9, 2023

It's paint loss (propably never thoroughly painted at assembly) used for the interior flocking. Won't affect anything.

retina_restoration · Feb 9, 2023

beemermark said:
It's paint loss (propably never thoroughly painted at assembly) used for the interior flocking. Won't affect anything.

No, this is clearly balsam separation of the cemented elements.

reddesert · Feb 9, 2023

Sometimes lens element separation that looks very reflective at a glancing angle has little effect when viewed straight-on, as image forming light passes through the lens. Sometimes it is highly visible face on and then it is likely to scatter light and cause reduced contrast and increased flare. So for example, the second to last picture straight on with the red circled area concerns me more than the last picture. But either way, the lens is not in "good" condition so you would have to try it and/or pass it on to someone who likes to experiment.

xkaes · Feb 9, 2023

Exactly. It may or may not be a problem -- so test it. Also, it may or may not get worse in time -- so I'd dump it.

BMbikerider · Feb 9, 2023

I will go along with balsam separation as well. If you look at the lens with both caps off with the diaphragm blades open and shine a directional bright light through from the front to the back or back to front, you may also see quite bad haze (like a foggy veil) with a halo, or what look like swirling cleaning marks which are not visible without the light.

How do I know this? Well I have just had to condemn a Nikon 35/70AFD F2.8 lens because of this which is irreparable separation.............Oh yes it can be repaired......but the cost which will be more than the lens is worth. It will be cheaper to buy another. (If I can find one)

Lemur · Feb 21, 2023

Hello. Thank you for the comments!

So, it seems that most people think it is about separation.

Here are other photos:

So basically, repairing this separation is very expensive and it is not worth the money considering the lens, right? Anyway, I could ask a lens repair service in my city.

And does this separation progress gradually or it always stays like this?

Lemur · Feb 21, 2023

Can you see the photos? Sometimes I can, but when I refresh the page sometimes I see just a symbol and a text without the image.

xkaes · Feb 21, 2023

That's a much better shot.

It doesn't matter if it is separation or fungus -- it's NOT worth fixing or using. And no matter what it is, it's going to get worse anyway.

Lemur · Feb 21, 2023

Here are some quick photos.

They are taken with a Fujifilm XT3 and a Nikon to Fuji adapter.

This lens was never very sharp. I bought it used like 15 years ago. I think this stain was not present, I guess I would have seen it.

Recently I compared it to an old manual Nikon 200 mm to make a video shot with my Fuji XT3. And the Nikon was much sharper and contrasty and it showed much better colors. The image of the Sigma was also greenish.

But that could be the case even if the Sigma was in perfect condition. So I don’t know how much this “separation” is affecting the image.

Lemur · Feb 21, 2023

I am not seeing the images. I don't know what is happening. My Internet connection is working very slow and I don't know if the forum interface is working correctly.

Sirius Glass · Feb 21, 2023

It appears that with that lighting there are no artifacts. Now check it in bright sunlight and with bright sunlight coming directly into the lens.

xkaes · Feb 21, 2023

One factor that needs to be considered is the aperture of the lens for the photo. Wide open the results would be worse compared to stopped down because the problem is worse on the edge(s). So if you always stop down the lens, it might be usable -- but the separation or fungus will get worse and worse over time, and so will the results.

But if you were always wanting a soft-focus lens, keep it, and use it opened up.

fiska · Feb 21, 2023

Looks like separation; also I don't think it's very hard to take off the bottom element. You need a rubber opener but it could be cheap. Like 25 dollars US.

Chuck1 · Feb 22, 2023

It actually looks like separation and dust (or a pre-fungal haze) (which could be just dust (but might turn into the snowflake or super fine hairy fungus- as dust is how fungal spores get in there and would then bloom with just a trace of moisture? that's my understanding-please correct me if I'm wrong-anybody )
In high school(before digital) I worked the counter at my local camera repair shop (which was reputable) they would not have been willing to uncement,clean and recement that group of elements in an off brand lens, If they would be willing to try it with a holy-grail(rare and expensive) lens it would have been at the clients risk
if you're looking to sell, it's not worth much and the market is way down, if ebay is an economic indicator, things don't look good.
It could produce a beautiful flare(at the magic angle of incidence-that is both BS and true- with an image that shows motion (or a second flash curtain sync)-techniques I have seen successfully at a critique, but the practitioner was tight lipped as to the process-basically they were stunning images (and I wanted to be able to do that)
good luck

Stain at the back of a lens. Fungus?

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