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[OM] Re: How best to determine effect of fungus on final print

Subject: [OM] Re: How best to determine effect of fungus on final print
From: "Wayne Culberson" <waynecul@xxxxxxxxxxxxxxx>
Date: Sun, 4 Dec 2005 14:27:21 -0400

> Over the last two years I've accumulated a supply of fungus infected OEM
> and 3rd party 35mm lenses, primes and zooms, in mounts for all of the
major
> brands including Olympus.  Some of the fungi are the small, circular
> looking kind, some are spider webby and other look like splotches.  Some
> lenses have only one or two elements affected while others show more
> extensive damage.
>
> Would it be preferable to use color or b&w print film?

In testing lenses, it seems that print film isn't really the way to go
because of the way most auto print machines "correct" the color, the
variations of printing process, and because the resolution of print films is
often less than what the lens can produce. Slide film seems the more
accepted way, but is also more expensive I suppose. Putting the lenses on a
digital body might be cheaper, if you have one.
>
> Would it be better to take photos of a monotone surface? Something like an
> off white or gray piece of fabric or a wall painted in a neutral color?
My
> thinking is there'd be no other "subject matter" to mask the fungus.
>
> What size print would be necessary to allow one to see the fungus?  4x6,
> 8x10, 11x14, larger?
>
> Would a small, medium or large aperture be better?
>
> With zooms would it be better to use the short, mid or long focal length?

It doesn't seem like it would be a test that would really tell you much
unless you shoot at all apertures, especially the largest ones, and at least
the two extremes of the zoom lenses. Most people testing lenses shoot a test
chart, or map, or something like a brick wall. But then they aren't looking
for the effects of fungus. Again though, if you don't shoot something like
these, I can't see that the tests would have much meaning.
>
> For zooms with a macro or close up feature would this setting show fungus
> better?
>
> Any thoughts, opinions, personal experiences appreciated.
>
> Gary

It would seem the best test might be to test the lens before and after
cleaning the lens, but otherwise under the exact same conditions. Then
report back to us if the fungus really had much degrading effect. I can't
seem to think fungus could do anything positive. But then I suppose if the
fungus infected lens gave some special look that you liked, you'd have to
try regrowing the fungus :-)

Two evenings ago I was reassembling a Vivitar 28-90/2.8-3.5 Series 1 lens.
When I got it all back together and looked into the front element, I was
disgusted with myself for being so careless as to have left an obvious
fingerprint on the inside edge of the front element group. It was really
obvious when viewing against the blackened interior. Anyways, I at first
reasoned that it wouldn't matter much, as it was only about 1/4 inch in on
one edge, and was obviously out of the optical path except when the lens was
zoomed almost to, or to, its 90mm setting. I tried reasoning myself into
just leaving it alone, but then knew I'd never be happy, so I took it apart
again to clean the fingerprint. Well, the fingerprint wasn't so obvious when
it was apart, but the frustrating thing is it wouldn't clean off. On closer
inspection, it was fungus, not a fingerprint, and a different sort of fungus
than I'd seen before. I remembered Clint's suggestion of using nose grease,
which removed it with no problem, and after cleaning the area further with
alcohol, I could see no permanent damage.

I was glad I hadn't left it alone, as it might have spread. So the question
is, Why not clean the fungus from the lenses? I don't think I'd ever be
happy using a fungus infested lens. I know some say it doesn't spread from
one lens to another, but I don't even like to attach one to a camera body.
And even if the lens tests good with it's present fungus, it doesn't mean
much as the garden in the lens will likely keep progressing anyways. Just my
opinion.

Wayne





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