Summicron 40mm Fungus?

Rororob · Sep 9, 2016

Hi,

i sucsessfully cleaned and lubricated the focussing mechanism of my Summicron C 40mm. While doing this, i thought i check out the lens elements and pointed a light through it. Well - because the lens takes sharp pictures and is contrasty even in tough light conditions ( i use a shade ) i thought it´ll be okay. But then i saw this on the inside of the rear lens (photographed through the front lens):

Im not quite sure what that is. It looks like scratches - but its defenetly on the inside (i think I´m the first one opened it). So i guess its a sort of fungus. The other lens elements show little haze on the borders. When i look through it, without a light it looks perfectly clean.

I took out the rear element and i can unscrew a ring of the back of it but thats it. Has anybody a tip, how to reach the last of the 2 rear element lenses? The first one - a cemented duplet is clean. It looks like its pressed and/or glued in.

I think about leaving it like it is, because it takes good pictures - but im afraid it will get worse. So if its a managable cleaning i will do it.

Thank you,
Robin

shutterfinger · Sep 9, 2016

Can you post some pictures of the rear element removed from the lens assembly?

Theo Sulphate · Sep 9, 2016

Looks like scratches to me. Fungus is organic and has an appearance of either fractals (like snowflakes) or "worm crawling".

If you're not the original owner, maybe the lens has been apart before and someone cleaned it improperly.

Welcome to APUG.

Alan W · Sep 9, 2016

Very straight lines lead me to believe its not fungus.If the lens is satisfactory,as you say,I wouldn't mess with it anymore.Results,and not looks,are what count.

paul ron · Sep 9, 2016

is that on the inside of the rear cell?

if it is.. fungus!

Rororob · Sep 10, 2016

thats what I thought as well. The lines are so straight, it can't be fungus... But on the other hand no one can scratch such a tiny surface like this. It would be circular or all in one direction and also in the middle of the lens.
So I guess it's a strange form of fungus. It's inside the lens. Lens was pretty dirty (dust, sticky grease) and all rings spanned extremely tight with no marks, wear etc.

Here are some pictures of the element.

The affected lens

The unaffected duplet. One ring can be screwed out.

Rororob · Sep 10, 2016

The gap for the spanner wrench is to get the group out, not to open the group itself...

shutterfinger · Sep 10, 2016

On the side of the group with the ring looks to be solid casting. The ring appears to be for spacing.
On the spanner slot side there is an inner ring. The inner ring most likely screws in holding the cells in place. A form of thread locker was likely used so apply nail polish remover between the inner and outer rings and let it sit for a few minutes before attempting to unscrew it. Rubber strap wrenches or a rubber stopper that contacts only the inner ring's inner surface may be needed to unscrew the inner ring. The only other assembly technique was to crimp the cells in place. The group barrel does not look crimped on either end.

Grytpype · Sep 11, 2016

I'd have said it could be coating damage due to over-aggressive cleaning by someone who has been into the lens before you, though it's a bit worrying that it seems to be worse near the edge, where fungus likes to start! I agree that the straight lines are very unlike fungus.

If it was fungus, you would normally be able to see it easily when you look straight through. If it's just some missing coating, it probably won't have a huge effect on pictures.

paul ron · Sep 11, 2016

how could it possibly be over zealous cleaning?
then the question begging to be asked.. why inside a cell and nothing on the outside glass? who cleans inside more than outside? If it was that aggressive cleaning, then the OCD user would have sanded the outside coatings as well.

Fungus grows in many shapes n forms, straight and webbed... shape is not a determining factor, where its happening is more important in this case. Typically inside the lens is where it starts.

being its close to the edges, it may not have as much an impact on your image other than flare n a soft focus when shooting wide open. Use a hood.

shutterfinger · Sep 11, 2016

I have encountered similar on the inside of a rear lens cell. Once disassembled I sat the affected cell in sunlight for 24 hours over 2 days then cleaned it. The cell looked new from all angles with magnification (loupe) once cleaned.

Summicron 40mm Fungus?

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