Re: B&L Stereozoom 7 Objectives

On Aug 27, 1:59 pm, Richard J Kinch <ki...@xxxxxxxxxxx> wrote:
Joe writes:
Thanks to all who have replied so far (and to those who will reply in
the near future).

Well, now I've encountered something quite similar today with spoiled
lenses.

I received a couple of old enlarger lenses today. On inspection, the
front surface had a kind of smeared look, like a film of clear grease,
but hard and resistant to cleaning. I did the usual cleaning, which
didn't seem to take it off, and finally disassembled the lens to get the
glass element out. After some increasingly aggressive cleaners
(starting with butyl cleaner, then naptha, xylene, CLR, and finally
potassium hydroxide) I managed to clean the smear off, revealing an
etched area where the smear had been.

I suspect this is a type of fungal adherent and damage. It was in an
annular pattern that mostly spared the center of the lens, as if it grew
on contaminants that were at the edge of the lens that's hard to clean.
This is not the usual spidery-filamentary growth you see inside a lens,
but a kind of surface *** that appears like a creeping mycelium
(http://en.wikipedia.org/wiki/Mycelium).

I'm still trying to figure out this lens fungus business. This guy
seems to have some respectable scientific analysis, versus the
superstition that a lot of photographers harbor:

http://www.mypentax.com/Fungus.html

No doubt lens fungus is a real problem, but it still baffles me that
lenses have this peculiar vulnerability to it, to the point of utter
ruin. In advanced cases, the fungus isn't just there to be cleaned off,
but has etched and ruined the optical surface.

I've seen this kind of damage a lot here in the southeast. Its common
to see older camera lenses from the coastal regions with damage from
bacteria or molds. They grow on the coating material, appearantly,
and the damage is impossible to get rid of.

I haven't seen this on microscope lenses, there is a huge difference
in the use of microscopes and cameras.

Thanks

Kevin Cunningham
SMS

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