swisspace wrote:
> How do I tell the difference, i just looked at the front element in
> bright light and you dont see anything yet when i looked before it has
> light spots that looked as if they could be fungal blooms, but having
> not seen an infected lens before I don't know how to tell.
-------------------------------------
Look through the lens from both ends using a flashlight pointing toward
your eye from the opposite end. This is a very severe test so look
through some of your other lenses that you *think* are OK as well.
You'll probably spot all sorts of dust and debris some of which may be
small black paint flecks. The dust and debris may be unsightly but does
no optical harm of any consequence.
Fungus will show itself as a spidery web or as an irregularly shaped and
possibly irregularly colored grayish blotch. Remember if you need
glasses for reading that the distance from your eye of the defects
you're looking for may not be withing the focusing ability of your eye.
Also, the apparent distance will be different from the actual distance
since you're looking through one or more lens elements.
A small amount of fungus will not do any optical harm of conseqence
either except that it may very well grow in the future. It also eats
coatings under the glass and may etch the glass itself since it produces
acid byproducts. The biggest harm is to your wallet. Even if there's a
tiny spot of fungus which is of no optical consequence the lens becomes
next to worthless.
Chuck Norcutt
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