What is THIS ?

[luigi bertolotti]

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Never seen on  any of my many lenses... 🤔

Front element of my APO TELYT 135 , after about one month during which the lens stood - unused - into my normal Leitz leather bag, with both caps.

 Apparently, the "sign" is on the back surface of the front element (which is single - not a coupled group) - the front surface looks and feels unscratched, as it must be.

The lens still "works right" evenif I haven't yet made specific comparision with another "clean" 135 (haven't another AT, of course... 😁 but will compare towards TElmar and or TElmarit)

Two phone pics from different angles.

 

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[AndreasG]

Does the second lens move forwards while focussing? The damage looks like after a mechanical impact on the internal lens surface.

[UliWer]

From the spot‘s spread on the first picture I‘d guess it is fungus. Though the white dots on the second look as if something mechanical had hit the lens - which would be very odd if it’s at the rear side of the lens element. 

[wizard]

No, certainly no mechanical damage. It looks like some kind of residue, could be due to condensation within the lens. I fear, however, that this may be fungus, as on the first image it seems as if the coating layer has been etched away by fungus. I do not think you will notice any effect on image quality, but the front element should be cleaned soon to avoid further damage or fungus spreading.

[pgk]

As ever it is difficult to be specific without seeing the lens however to me this looks like either physical damage followed by coating degradation, or possibly contamination by something which is causing a residue (damp?) to spread. It does not look like fungus which spreads in obvious tendrils. Nor is it likely to be caused by the second element as if it was the damage would be central where they would meet first (I doubt that they could anyway). At a guess, either the front element may have been damaged sometime in the past, obviously after it was coated, and the conditions in your bag may have been such that the damage has now become more obvious and has revealed itself and become noticeable. Or, something has been sat within the lens and has now moved and is now obvious and is causing an issue with the coatingg due to deliquescence. I would get it looked at, probably by Leica because unfortunately, if I am right, it might at worst need a replacement front element and I doubt that anyone else can supply one. If its contamination then it will simply need a good clean although you still need to know what has caused it.

[250swb]

I think it's probably fungus. I've always been leery of storing lenses in leather cases but that may not be the trigger for fungus. It's all around us and inside all our lenses, but it needs the right environment to start growing, a little humidity and darkness is a typical scenario. And it comes in many forms, not all appear as tendrils, some forms look like a powdery deposit. 

[luigi bertolotti]

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Thanks to all : me too thought about fungus... and the leather bag, for several reasons took some very warm days, though never in full sun : does someone know if the front element of the AT 135 is easy to dismount with not too arcane tools ? I would like to give a look by myself before traveling to Milan where is the nearest good lab...

[UliWer]

I actually looked at my Apo-Telyt - and I shouldn‘t dare to try removing the front element. I’d rather recommend to send it directly to Wetzlar. It will perhaps take several months until you get it back. This lens lives and dies on precise adjustment. 

[wizard]

vor 31 Minuten schrieb luigi bertolotti:

does someone know if the front element of the AT 135 is easy to dismount with not too arcane tools ?

I am pretty sure the front ring may be unscrewed using suitable pliers (there is always the risk of scratching the front lens in the process though. Happened to one of my lenses even at Leica in Solms, they then exchanged the front lens element for free), and once unscrewed, access to the front lens element should be easy (it might simply fall out when the lens is reversed). Since this is an expensive lens, I personally would not try to open it myself.

P.S.: I happen to have my own Apo-Telyt right here, and just had a look at it. The construction is different from the usual screw-in ring. There is a very small screw visible at the front of the lens, which seems to go through a front ring. No idea what happens if you unscrew that tiny screw. Maybe the ring can then be removed, but maybe there is another element that will have to be removed, too, before the front lens element may be taken out.

Edited November 6, 2023 by wizard

[AndreasG]

I got another theory:

Moisture in the lens

Lens stored vertically with the front lens down

Condensed moisture builds a small puddle in the concave front lens

Water dissolves the coating, maybe together with fungus

The puddle dryes slowly and leaves the white, somehow crystalline residue

 

Edited November 7, 2023 by AndreasG

[Erato]

19 hours ago, luigi bertolotti said:

Thanks to all : me too thought about fungus... and the leather bag, for several reasons took some very warm days, though never in full sun : does someone know if the front element of the AT 135 is easy to dismount with not too arcane tools ? I would like to give a look by myself before traveling to Milan where is the nearest good lab...

APO TELYT 135 is a great lens. Send it to Leica for a brand new coating(refurbish) if estimated cost is reasonable.

[luigi bertolotti]

10 hours ago, AndreasG said:

I got another theory:

Moisture in the lens

Lens stored vertically with the front lens down

Condensed moisture builds a small puddle in the concave front lens

Water dissolves the coating, maybe together with fungus

The puddle dryes slowly and leaves the white, somehow crystalline residue

 

Very probable you are spot on : The lens was indeed into the bag, vertical front down (with cap)...and for my lack of attention it stood like this - bag closed , surely also in warm and humid environment.

 

[Ronazle]

Yes, it does look like a patch of damaged coating.  I suspect if that is the case, Leica would just replace the front element and align it properly and at their leisure add it to a recoating group.  The only (so I think, not a fact) time it is profitable or wise to re-coat a front element is when they (the front element is no longer available and the lens is valuable) are no longer available.  To re-coat the old coating has to be removed and the glass polished prior to re-coating.  If the degradation has depth, the required polishing could be too extreme for treatment by re-coating. Nothing I have said is a particularly rigid fact, just my previous experience with a 50mm Summicron that did get a rather expensive recoating.  Best of luck on the lens....by all means let us know the outcome and please tell me if anything in the foregoing I wrote is in error. Regards, Ron

Edited November 10, 2023 by Ronazle
clarity