What's this on the glass?

[raining_macondo]

Hi, RFFers,



Would you please help me recognize what's this on an internal surface, I have circled it out in the picture, it's like a nebula-shaped thin patch of droplets(or solid)? Is it removable? Will it affect image quality?

I have seen this from other lenses too I remember. This lens obviously has been opened before.

 

[TenEleven]

This seems as it could be three things, that from my experience look like this. However a visual will only tell you this much - the proof is in the pudding - aka when you try to clean it.

1. It could be some sort of coating damage - either by excessive wiping or fungal etching (this is my best bet)
2. Some sort of alteration in the cement, if this is indeed a bonded element - it would help to know more about this lens and its history
3. Some sort of residue that could be possibly wiped off, however I do not think it's out-gassing of oil from the aperture blades as that usually has a much more regular shape and distribution

 

[raining_macondo]

TenEleven

Thanks a lot for your reply.

The thing is recently I don't have access to any tools, and I will either keep it or return it soon. I am thus trying my luck here.

This is a 60's MOG Trioplan, no cement. This patch looks as if an aggregation of indistinct dried droplets, with several bigger ones having much more clear space around them (which is why it looks uneven in the picture). At first I believed it was just cleaning liquid residual left by cleaning pad, but then there should have been more streaks and the texture more even. So I am confused, too.

 

[TenEleven]

Yeah I'd try the lens first. It's the only way to know for sure.
I also like to keep some cheaper not-perfect lenses around - especially for using in "dangerous" environments such as the beach or in light rain.

I've found that the effect of such impurities really depends on the lens design and where on the lens (which glass surface) the imperfections are. I have some lenses that look pretty bad and can't be cleaned - yet - the effect is completely invisible compared to a "good" copy. Yet on the other hand I have some lenses where there are only seemingly minor imperfections but the effect on the depiction is strangely large.

 

[Sonnar Brian]

Agree with everything stated- the only way to know for sure is to open the lens and try to wipe the marks off. It is probably just haze- but you never know if it is something etched into the glass until having access to it.