Separation or fungus?

[Roger Hesketh]

I am assuming this has to be separation given that it is located within the rear group of a lens of Tessar design. It does however look to my untutored eye rather dendritic. More so than the picture shows. I have thankfully been free from either apart from a little crystalline separation on some Gundlach Turner Reichs I have so do not know what to make of this. I would appreciate your opinions.




Also I wonder if anyone recognises the focusing mount this lens,the same lens, is mounted in.



The Dallmeyer catalogue says it will cover quarter plate which is probably rather conservative give it is 6" lens which they also say will cover an angular field of 50 degrees. Every one of these lenses I have seen pictures of is mounted in a focusing mount for motion picture use and this one appears to be too, but different from any of the others I have seen. The lens board is part of the mount. Just curious that's all. Thanks in advance.

Roger

[Leigh]

We need a much clearer, well-focused image in the first case.

- Leigh

[Roger Hesketh]

We need a much clearer, well-focused image in the first case.

- Leigh

You're right I do beg your pardon. It looked sharp enough to my beer fuddled mind late last night but was clearly beyond the close focusing capabilities of the digital compact I was trying to use and my ability as a photographer to capture. In truth even a well focused image does not impart much more information as the lens flaws are clear, very nearly transparent, and when the lens is tilted to make the flaw visible to the camera all the fine detail is lost. In the clear light of day it would appear to me to just be a balsam flaw but an unusual one.



This picture is not much better. Could a moderator please delete this thread. Sorry for wasting everyone's time.

[IanG]

It's not separation, it looks organic in it's growth, theirs different fungi/mold attacks.

I have a similar size plain sunken mount Dallmeyer 6" f3.5 lens, mines just marked as a Press lens, it's on a Dallmeyer light weight press camera (a re-badged Ensign).

Ian

[Steven Tribe]

The original photo was more than good enough!

Usually described as "fern/coral" growth in the balsam layer! In spite of appearances, it is a crystalline chain reaction. That is, something is being precipitated from the aging balsam which grows in much the same way as a snowflake does. There is no evidence of it having bacteriological or fungii catalyst cause - But it is possible.

There are no evil effects on glass and it disappears along with old balsam.

You are certainly not wasting our time!

[hoffner]

Thanks Steven,
for the good words to the OP. I had the suspicion it was ageing balsam but having not experience enough I didn't vociferate about it. But as much I know that even if the OP took pictures with the lens it would not show up. These defects are surprisingly forgiving.

[Leigh]

As a comparison...
Fungus generally appears as thin tendrils, radiating from the original point of infestation.

There's a current thread about fungus with some photos: http://www.largeformatphotography.in...ghlight=fungus

- Leigh

[Jim Noel]

Definitely fungus.
The focusing mount is likely off a film pack camera, but I have no idea as to which one.

[Fotoguy20d]

I like Steven's answer personally (not that I know if he's correct or if the correct answer is fungus). I have a Wolly Tele-Optar which has a "snowflake" like that in the front cement pair. I'd always assumed it was fungus but Ive owned the lens for a couple of years and it hasn't grown (despite being locked up in a UV safe box) or changed in that time so maybe not.

Dan

[Francisco J. Fernández]

yes, are fungi.

spores are in the air when the lenses were assembled. cement is tight for years (balsam of Canada and other substances) but one day, a slight separation between the layers of lenses.
allows entry from a little water (humidity) and spores grow following several patterns. threads, dendritic, and others. They feed on balsam and mineral layers Multi Coated, or Coated ... when the water runs out, the fungus is stops growing. but the food brand is forever on the surface of the lens.

Why the shape looks growth crystal? because this feeding pattern on glass, and the fungus is eating balm minerals besides other salts.

dendritic shapes commonly grow in the way of animals, plants and minerals.

It is a growth that uses the space available.

Following is a fractal growth patterns . that occurs from molecules to galaxies . at all scales (part of the golden sequence, or Fibonacci sequence. Phy number ... the number of God).


When the lenses are removed , are detached from them, drawing patterns are more continuous . Son of sinusoidal edges ... and usually have very frequently Newton rings , which are sometimes colored .