Schneider dust & cleaning

I was looking @ a used Symmar 135mm the other day.
It was cheap because ...
.... when looking straight through it there was a dust on the elements.
But the dust wasn't dark. Rather it sparkled.
Is this from the glues & would it be practical to clean it?

Collin (always looking for a bargain) Brendemuehl

Collin Brendemuehl wrote:
I was looking @ a used Symmar 135mm the other day.
It was cheap because ...
... when looking straight through it there was a dust on the elements.
But the dust wasn't dark. Rather it sparkled.
Is this from the glues & would it be practical to clean it?

Collin (always looking for a bargain) Brendemuehl

A large format lens comes in two groups, each of which is screwed into
the shutter. Either can be removed and you ought to be able to clean
dust from the exposed surfaces. But you certainly don't want to take
either group further apart to get at the internal surfaces. That would
have to be done by an expert in a clean room. In any case, such dust
is only going to produce some flare, which may lower contrast slightly,
but otherwise is probably inconsequential.

Having said that, let me add that I have taken apart a Mamiya C3 180 mm
lens which had some crud built up on the internal elements, and I
managed to clean them and put the lens back together. But I was
willing to sacrifice that lens if I messed up. also, since the it is a
TLR double lens, I got to practice on the taking lens first. I wouldn't
try it with any of the large format lenses I actually plan to use
extensively.

"Collin Brendemuehl" wrote in message
om...
I was looking @ a used Symmar 135mm the other day.
It was cheap because ...
... when looking straight through it there was a dust on
the elements.
But the dust wasn't dark. Rather it sparkled.
Is this from the glues & would it be practical to clean
it?

Collin (always looking for a bargain) Brendemuehl

Can you tell where the "dust" is? The speckles _might_ be
small voids in the cement or something metallic. It could
also be small pits in the glass due to etching from fungus
or condensed moisture. Use a loupe and flashlight to examine
the surfaces. These will also show if the speckles are on an
inside surface.
As far as cleaning, it depends on what you are dealing
with. However, in general, its possible to clean all the
lens surfaces. Symmar lenses have retaining rings on both
outside elements. They are not difficult to remove unless
the barrel is dinged. Symmars often have spacers under the
front element. Lift the element out with sticky tape so you
can keep track of what is under it. The f/5.6 Symmar is a
Plasmat lens. The outside component is two elements cemented
together, the inside component a single element. Some of the
newer lenses are more complex, see the drawings on the
Schneider of America site at http://www.schneideroptics.com
Typically, older lenses can get hazy inside. The haze
cleans off easily with lens cleaner or alcohol. Sometimes
one finds flakes of the anti-reflection paint inside the
cell. These also clean off easily but you should inspect the
inside of the cell to see where the paint came from. Another
common problem with Schneider lenses from the mid 1950's and
later is flaking edge paint on the elements. When the lens
is assembled this looks like bubbles around the very edge of
the lens. It does little if any harm but if the lens is
disassembled for cleaning the old paint should be cleaned
off and replaced. The best anti-reflection paint is Krylon
Ultra-Flat Black. This is available in spray cans. Spray
some into a small container and apply it with a brush.
If the lens is pitted there is nothing that can be done.
The pits are generally too deep to repolish the lens plus
such repolishing is expensive.
The flashlight and magnifier are musts when examining
lenses.

--
---
Richard Knoppow
Los Angeles, CA, USA

"Richard Knoppow" wrote in message
link.net...

"Collin Brendemuehl" wrote in message
om...
I was looking @ a used Symmar 135mm the other day.
It was cheap because ...
... when looking straight through it there was a dust on
the elements.
But the dust wasn't dark. Rather it sparkled.
Is this from the glues & would it be practical to clean
it?

Collin (always looking for a bargain) Brendemuehl

Can you tell where the "dust" is? The speckles _might_ be
small voids in the cement or something metallic. It could
also be small pits in the glass due to etching from fungus
or condensed moisture. Use a loupe and flashlight to examine
the surfaces. These will also show if the speckles are on an
inside surface.
As far as cleaning, it depends on what you are dealing
with. However, in general, its possible to clean all the
lens surfaces. Symmar lenses have retaining rings on both
outside elements. They are not difficult to remove unless
the barrel is dinged. Symmars often have spacers under the
front element. Lift the element out with sticky tape so you
can keep track of what is under it. The f/5.6 Symmar is a
Plasmat lens. The outside component is two elements cemented
together, the inside component a single element. Some of the
newer lenses are more complex, see the drawings on the
Schneider of America site at http://www.schneideroptics.com
Typically, older lenses can get hazy inside. The haze
cleans off easily with lens cleaner or alcohol. Sometimes
one finds flakes of the anti-reflection paint inside the
cell. These also clean off easily but you should inspect the
inside of the cell to see where the paint came from. Another
common problem with Schneider lenses from the mid 1950's and
later is flaking edge paint on the elements. When the lens
is assembled this looks like bubbles around the very edge of
the lens. It does little if any harm but if the lens is
disassembled for cleaning the old paint should be cleaned
off and replaced. The best anti-reflection paint is Krylon
Ultra-Flat Black. This is available in spray cans. Spray
some into a small container and apply it with a brush.
If the lens is pitted there is nothing that can be done.
The pits are generally too deep to repolish the lens plus
such repolishing is expensive.
The flashlight and magnifier are musts when examining
lenses.

--
---
Richard Knoppow
Los Angeles, CA, USA

"Collin Brendemuehl" wrote in message
om...
I was looking @ a used Symmar 135mm the other day.
It was cheap because ...
... when looking straight through it there was a dust on
the elements.
But the dust wasn't dark. Rather it sparkled.
Is this from the glues & would it be practical to clean
it?

Assuming this is really just dust and not something else, it may not be
important. All lenses seem to have a fair amount of dust in them. If you
hold a flashlight at one end of a brand new lens and look through the other
end you'll probably be shocked at the amount of dust you see floating around
in there. At least I was when a salesman at a camera store performed this
little demonstration for me.

On Wed, 10 Mar 2004 04:23:15 GMT, "Richard Knoppow"
wrote:


If the lens is pitted there is nothing that can be done.
The pits are generally too deep to repolish the lens plus
such repolishing is expensive.

If it's determined the pitting is causing image degradation and you
want to continue using the lens put some of that flat black paint or
india ink into the pits to block the light from being refracted
through them, assuming the pits are few and large enough to be
manipulated in this manner. A wood toothpick or a very fine sable
brush can be used for the application.
Do this with the understanding that it will cut the light transmission
of the lens to some degree and some testing will need doing to
determine what is called T-stops to keep exposure dead on. The amount
of correction will vary over the aperture scale depending on the
location of the painted areas.