| Author |
Message |
    
P. A.
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 09, 2004 - 04:45 am: | 
|
I occasionally come across lenses that have a multitude of tiny white (probably actually clear or translucent) 'spots' on them, which usually only show up when you look directly through the lens.
I've got an Agfa Clack with this problem on the inside of its meniscus lens. I can't tell if it's some sort of damage to the coating, or fungus or what. Does anyone know?
I've tried using Windex, generic 'lens cleaning' fluid (probably alcohol) and hydrogen peroxide on the thing, but nothing will remove it. I had a filter once with this problem, and I finally removed it with acetone, but I'm reluctant to put that on a lens for fear of ruining the coating.
Does anyone have any insights? |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, May 09, 2004 - 10:02 am: |
|
This sounds like one of the many appearances of lens fungus. Methods of removing it have recently been discussed here - just search the archives for 'fungus'. |
Brian Wallen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, May 10, 2004 - 12:22 am: |
|
There is an illustration of advanced fungus on this page:
http://www.staff.uiuc.edu/~b-wallen/BN_Photo/GenTechLenses.htm
If you can get the lens elements under a low-power microscope, you can see if they have a kind of webby, frostlike structure characteristic of fungus. If fungus eats through the coating, it will leave spots after the fungus itself is removed, but those are usally clear--just the absence of the coating.
I've had good luck with ammonia and lighter fluid removing fungus. I'd be very wary of acetone. |
David Nebenzahl
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, May 10, 2004 - 10:45 am: |
|
Acetone is perfectly safe to use and won't harm lens coatings. Another method of attack is the canonical application of cold cream--yes, that's right: ordinary Pond's, left on the glass for some time, then cleaned off.
I'd suspect that spots on a lens as you describe are not fungus; Brian correctly described fungus, which usually leaves a characteristic spider-webby appearance behind.
And in the worst case, even if the coating is gone from the front element in spots, the lens will still be perfectly usable. Just a little more prone to flare from backlit subjects is all. |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 11, 2004 - 02:14 am: |
|
David, fungus may appear in many appereances. I once had some tiny whitish spots on a lens which had beens stored in a cold humid room for years. The spots could not be cleaned off with solvents such as lighter fluid etc but went off easily with a little vinegar. Actually it depends whether fungus will damage the coating or not. I had severe cases of lens fungus where it could be removed without leaving any traces, and some seemingly less severe cases (of just a few threads of fungus) where it had grown into the coating and left some bright reflecting (but perfectly transparent) traces.
The snow flake like structures are very common but not the one and only appereance of fungus. |
|
