Will this effect photo quality

connorgeoff · Aug 4, 2019

I just received a lens (Mamiya G 50mm) and on the back glass there is clearly something present (either balsam seperation or fungus)

From the photo attached does anyone know how this/if this will effect image quality.

I will test the lens, but in the essence of time I am looking for input from your past experiences

Thanks

KN4SMF · Aug 4, 2019

Photgraphing lens flaws effectively is very difficult. I don't see anything but normal reflections. But if you have to ask the question, you already know the answer. Do you have to wear glasses to see, like me? If so, you know what it is to have dirty glasses. Same thing.

RalphLambrecht · Aug 4, 2019

connorgeoff said:
I just received a lens (Mamiya G 50mm) and on the back glass there is clearly something present (either balsam seperation or fungus)

From the photo attached does anyone know how this/if this will effect image quality.

I will test the lens, but in the essence of time I am looking for input from your past experiences

Thanks

this will make no visible difference in image quality but, I'd clean it anyway.

billbretz · Aug 4, 2019

That sure looks like a palm or fingerprint to me (and easily cleaned).

Grim Tuesday · Aug 4, 2019

I assume the thing you are referring to is on the bottom of the rear element? Is it on the outside of the rear element? If you can clean it off, do that. If it's on the inside I'm honestly not sure what it is. It doesn't look like any kind of fungus I've ever seen and it barely looks like haze or separation.

Most lens issues (fungus, scratches) have minimal-if-any effect on image quality but this is a rare one that actually might just because it's big and on the rear element.

connorgeoff · Aug 4, 2019

Thank you for the insights so far.

It is not a fingerprint, whatever it is, it is on the interior.

2 questions:
When I test the lens are there any particular shots I should be taking?

If this does not have an effect on photos, how long would it be until is does? I assume these types of issues get worse over time

BAC1967 · Aug 5, 2019

Rear element problems have more effect on image quality than front element problems.

reddesert · Aug 5, 2019

I'm not sure what surface we are looking at in the picture. It does not look like fungus, which is a sort of spidery growth across the surface of an element. It looks like white spots on the black paint or coating at the edge of an element, internal to the lens. If so, this is something often called "Schneideritis" (occasionally Fuji-itis) in the world of large format lenses, a flaking or speckling of the light absorbing paint. If so, it's unlikely to affect image quality; it might affect flare if there is a way for light to fall on the surface. Whether you decide it's not worth bothering about or warrants returning the lens is your decision.

connorgeoff · Aug 5, 2019

Thank you for the replies.

@reddesert I'm very interested in your schneideritis observation. It is actually really hard to tell if the specks are on the wall or the element. I have attached more photos that do show that there seems so be an 'edge' where it stops, which would back up schneideritis.

The only problem is, that 'edge' seems to vanished when you move the lens around. You can see how it vanishes on the first photo also.

I am Interested in your perspective on the new photos. Again thanks

Ian C · Aug 5, 2019

In the photos of your post #9 the lens appears clear. The only untoward thing I can see is the tiny white spots that form on edge of the glass disks (often referred to as “Schneideritis”). These are benign. The edges of glass elements are coated with an opaque black coating whose purpose is to absorb light to prevent internal reflections from the edges.

As the material ages, it sometimes develops small white areas, often in the form of bubbles. It's also possible for these bubbles to be present and visible on a newly-manufactured lens.

It’s annoying to see, but has no effect upon the results. Here is what Nikon has to say of this:

https://www.nikonimgsupport.com/na/NSG_article?articleNo=000028608&configured=1&lang=en_SG

RalphLambrecht · Aug 5, 2019

connorgeoff said:
Thank you for the insights so far.

It is not a fingerprint, whatever it is, it is on the interior.

2 questions:
When I test the lens are there any particular shots I should be taking?

If this does not have an effect on photos, how long would it be until is does? I assume these types of issues get worse over time

If it is on an interior glass element, you have to have it professionally cleaned but, I'm not sure you'll notice a difference. take a few, for you typical, shots and see if you notice any ill effects.

AgX · Aug 5, 2019

To me it is neither finger prints nor Schneideritis. But sparkling of the painted rim of a lens element.

Your case is a very mild one and typical for most lenes.

But Schneideritis and rim sparkling are hard to differenciate in a photo of a lens of which we do not have at least a same model sample in hand.
Schneideritis affects the proper rays, rim sparkling only those rays that already gone astray.

jim10219 · Aug 5, 2019

Schneideritis. It ruins resale value, not photos.

Alan Gales · Aug 5, 2019

jim10219 said:
Schneideritis. It ruins resale value, not photos.

Yep. It's great if you want a lens at a budget price. Bad if you are the Seller.

AgX · Aug 5, 2019

Am still surprised that some of you are that sure of Schneideritis. I still see no proof of that in the photos.

connorgeoff · Aug 5, 2019

Thanks all, despite what this is, it sounds like this will not effect photo quality anyway.

I have taken some test shots and will post the results once processed

AgX · Aug 6, 2019

If it is Schneideritis the effect in worst will be as if the respective two lens elements would stand seperate and were not coated at their facing sides. And this all only in a sprankled manner and only at their circumference... In theory a minime reduction of contrast (a fraction of a fraction) is to be expected and that only as long not stopped down.
To be more precise: even a properly cemented pair of lens elements has some reflection at the contacting faces as the cement itself has a different breaking index, and in the two lens elements may vary in breaking index too, though this all is not as pronounced as a space with air or even vacuum.

connorgeoff · Aug 6, 2019

I got some film back today and quickly scanned the test photos i took, key notes below:

1. There does not seem to be significant impact on normal images.
2. When the sun is hitting the lens there does seem to be some slight haziness, look specifically at the colour change on the fence in photo 2 (1914003) (this is my opinion, I could be seeing things).
3. When directly shooting into the sun there is a clear ring that imitates the rear lens issue perfectly (same edge like cut-off, very similar actual size on the negative). I would usually expect flare from this angle, but this semi ring shape is clearly from the rear element issue.

For me this is an issue, happy to be told otherwise though, thats why I am posting here after all.

Thanks

AgX · Aug 6, 2019

I cannot relate that ring artefact to the issue with your lens. Maybe others make me wiser.

MattKing · Aug 6, 2019

AgX said:
I cannot relate that ring artefact to the issue with your lens. Maybe others make me wiser.

I agree. Anything at the plane of the artifact isn't going to image as a sharp, defined object. Any affect from it will be an overall affect - generalized flare and loss of contrast.
By the way, at the risk of pedantry, I believe that we are discussing whether the artifact will affect (not effect) the quality of your photos.

AgX · Aug 6, 2019

MattKing said:
Anything at the plane of the artifact isn't going to image as a sharp, defined object.

Yes, but there can be effect other than giving an image of the lens-element surface itself.

Namely, images and ghost images of extremely strong light sources. And with the sun in the photograph we got such source. And even such narrow ring is one of such ghost images. These are dampened by antireflective layers.
My doubt though is, that just the sprankled reflective patches at the circumference at a doublet (if that is the kind of artefact at all !) can produce or strengthen that ring.

But we going very academic now, especially without having that lens in hand.

connorgeoff · Aug 6, 2019

It might be hard to tell without holding the lens, but I will try and describe:

The speckling occurs in a ring about 5mm wide around the rear glass.

Moving from outward in: the speckling is disparate and becomes more concentrated as it moves toward the centre. So much so that at in the inner 0.5mm of the ring there is almost absolute coverage of speckling.

After this intense concentrated coverage of speckling there is a hard stop, and the glass is completely clear.

That hard edge/stop of speckling is where this bizarre flare is created. (You can see this 'edge' on the photos of the lens)

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