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Lens Cell Cleaning



 
 
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  #1  
Old February 10th 11, 01:26 AM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/9/2011 10:41 AM, Cheesehead wrote:

And the rear has a ring holding it in place, which should be removable
easily with a spanner wrench.


I'm not sure what you are saying here but do NOT remove the glass itself
from it's mount but unscrew the whole cell from the shutter to clean the
front/inner surface and you can also clean the rear of the front element
while you are there by opening the shutter.

Stephey
  #2  
Old February 10th 11, 04:41 AM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 752
Default Lens Cell Cleaning


wrote in message
...
On 2/9/2011 10:41 AM, Cheesehead wrote:

And the rear has a ring holding it in place, which should
be removable
easily with a spanner wrench.


I'm not sure what you are saying here but do NOT remove
the glass itself from it's mount but unscrew the whole
cell from the shutter to clean the front/inner surface and
you can also clean the rear of the front element while you
are there by opening the shutter.

Stephey


If its a standard Triplet the back cell will be a single
lens so there is no need to remove the glass. The front cell
will have two elements. Usually in larger lenses there is a
threaded back cap on the cell but it may have a retaining
ring on the front which is more common for smaller lenses.
If a back cap its easy to remove. The elements are clamped
between concentric edges in the cell so are automatically
centered.
If the cap is too tight for removal with simple finger
grip use one of those rubber jar grippers. It won't mar the
surface. If you grip too tightly it will clamp it and make
it even harder to remove.
I agree with the others about cleaning but if the lens
is oily the standard optical cleaner is pure acetone
followed by dry isopropyl alcohol. Window cleaner like
Windex may streak the lens if not followed by alcohol. The
newer butyl alcohol "streak-free" cleaners are better.
While ammonia is alkaline and strong alkalies can
dissolve some kinds of glass there is no real danger from
the very dilte ammonia in Windex and similar cleaners.
If you use acetone be careful of the edge paint, if any,
and of the paint on the cell because it will dissolve both.
I do not recommend cleaning inside elements when in a
shutter because there is too much danger of getting the
cleaning fluid into the shutter, take the cell out.


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



  #3  
Old February 10th 11, 09:53 PM posted to rec.photo.equipment.large-format
David Nebenzahl
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Posts: 1,353
Default Lens Cell Cleaning

On 2/10/2011 12:47 PM Cheesehead spake thus:

I'm not absolutely certain about the Geronar formula. It is reported
to be a Tessar.
That said, the rear should be a single piece of glass. But it is not.
If it is a cemented piece, then it is not a true Tessar and the
fogging may be in the cement.
That would be bad.
I've not found the formula out there to describe the lens.
In the mean time I've been searching for a replacement rear cell.


It's not clear you've tried to remove and clean the rear cell; have you?
If not, you should. What've you got to lose? If in fact the cement is
clouded (which I think is probably unlikely), you've got to replace the
thing anyhow (or have it recemented), so why not just pull it out and
clean it? It ain't rocket surgery, you know.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
  #4  
Old February 11th 11, 02:20 AM posted to rec.photo.equipment.large-format
[email protected]
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Posts: 428
Default Lens Cell Cleaning

On 2/10/2011 3:47 PM, Cheesehead wrote:


I'm not absolutely certain about the Geronar formula. It is reported
to be a Tessar.


Not sure who told you that but it's not a tessar, it's a triplet. A
modern version of the classic cooke triplet. And a rather good one I
might add.

Stephey

  #5  
Old February 11th 11, 03:01 AM posted to rec.photo.equipment.large-format
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Posts: 428
Default Lens Cell Cleaning

On 2/10/2011 7:54 PM, Cheesehead wrote:

I have, of course, unscrewed the cell from the shutter and observed
that the fogging is inside the rear cell.


Hmm that's odd. It should be a single element so hard to imagine there
being fogging inside it?

Stephey

  #6  
Old February 11th 11, 03:14 AM posted to rec.photo.equipment.large-format
David Nebenzahl
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Posts: 1,353
Default Lens Cell Cleaning

On 2/10/2011 4:54 PM Cheesehead spake thus:

On Feb 10, 4:53 pm, David Nebenzahl wrote:

It's not clear you've tried to remove and clean the rear cell; have
you? If not, you should. What've you got to lose? If in fact the
cement is clouded (which I think is probably unlikely), you've got
to replace the thing anyhow (or have it recemented), so why not
just pull it out and clean it? It ain't rocket surgery, you know.


I have, of course, unscrewed the cell from the shutter and observed
that the fogging is inside the rear cell.


Well, did you try to clean the outer surfaces? Sorry, not clear from
your postings.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
  #7  
Old February 11th 11, 03:50 AM posted to rec.photo.equipment.large-format
[email protected]
external usenet poster
 
Posts: 428
Default Lens Cell Cleaning

On 2/10/2011 10:14 PM, David Nebenzahl wrote:
On 2/10/2011 4:54 PM Cheesehead spake thus:

On Feb 10, 4:53 pm, David Nebenzahl wrote:

It's not clear you've tried to remove and clean the rear cell; have
you? If not, you should. What've you got to lose? If in fact the
cement is clouded (which I think is probably unlikely), you've got
to replace the thing anyhow (or have it recemented), so why not
just pull it out and clean it? It ain't rocket surgery, you know.


I have, of course, unscrewed the cell from the shutter and observed
that the fogging is inside the rear cell.


Well, did you try to clean the outer surfaces? Sorry, not clear from
your postings.



I'm confused on his post as well. It's a triplet and as such the rear
"cell" would be a single element. I suppose the glass itself -could- be
bad and have fogging inside the single element itself? Or the coating is
screwed up?

Stephey
  #8  
Old February 11th 11, 04:03 AM posted to rec.photo.equipment.large-format
David Nebenzahl
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Posts: 1,353
Default Lens Cell Cleaning

On 2/10/2011 7:50 PM spake thus:

On 2/10/2011 10:14 PM, David Nebenzahl wrote:

On 2/10/2011 4:54 PM Cheesehead spake thus:

On Feb 10, 4:53 pm, David Nebenzahl
wrote:

It's not clear you've tried to remove and clean the rear cell;
have you? If not, you should. What've you got to lose? If in
fact the cement is clouded (which I think is probably
unlikely), you've got to replace the thing anyhow (or have it
recemented), so why not just pull it out and clean it? It ain't
rocket surgery, you know.

I have, of course, unscrewed the cell from the shutter and
observed that the fogging is inside the rear cell.


Well, did you try to clean the outer surfaces? Sorry, not clear
from your postings.


I'm confused on his post as well. It's a triplet and as such the rear
"cell" would be a single element. I suppose the glass itself -could- be
bad and have fogging inside the single element itself?


No, it could not. Glass itself doesn't fog, at least not under most
conventional terrestrial* conditions.

Or the coating is screwed up?


Is that lens even coated? Even if so, coatings don't generally fog.
Either the lens surfaces themselves are schmutzified (that's the
technical term), or it's a cemented element and the cement has gone bad.

If the latter, the elements can be separated and recemented. This
process has actually been described here by R. Knoppow. People like S.
Grimes can also perform this particular kind of alchemy.


* Sorry, been reading about black holes and other weird cosmological
phenomena, where anything can happen.


--
Comment on quaint Usenet customs, from Usenet:

To me, the *plonk...* reminds me of the old man at the public hearing
who stands to make his point, then removes his hearing aid as a sign
that he is not going to hear any rebuttals.
  #9  
Old February 11th 11, 06:03 PM posted to rec.photo.equipment.large-format
[email protected]
external usenet poster
 
Posts: 428
Default Lens Cell Cleaning

On 2/11/2011 8:27 AM, Cheesehead wrote:


that also has me puzzled. It is described as a Tessar, but I am only
going by what I can find.


Where did you see that? EVERY source I found, except people saying they
are guessing at the formula, like you are here, say it's a triplet.

http://www.apug.org/forums/forum44/1...8-geronar.html

http://www.hevanet.com/cperez/test/BigMash210.html

http://www.bhphotovideo.com/c/produc...nar_Copal.html

http://greenspun.com/bboard/q-and-a-...?msg_id=002Owe

http://en.wikipedia.org/wiki/Rodenstock_GmbH#Geronar

http://photo.net/large-format-photography-forum/003EZO

The rear cell *looks like* it has two elements in it.


Not sure how that is possible.

Stephey

  #10  
Old February 11th 11, 07:20 PM posted to rec.photo.equipment.large-format
Richard Knoppow
external usenet poster
 
Posts: 752
Default Lens Cell Cleaning


"Cheesehead" wrote in message
...
On Feb 9, 11:41 pm, "Richard Knoppow"
wrote:

If its a standard Triplet the back cell will be a single
lens so there is no need to remove the glass. The front
cell
will have two elements. Usually in larger lenses there is
a
threaded back cap on the cell but it may have a retaining
ring on the front which is more common for smaller lenses.
If a back cap its easy to remove. The elements are clamped
between concentric edges in the cell so are automatically
centered.
If the cap is too tight for removal with simple finger
grip use one of those rubber jar grippers. It won't mar
the
surface. If you grip too tightly it will clamp it and make
it even harder to remove.
I agree with the others about cleaning but if the lens
is oily the standard optical cleaner is pure acetone
followed by dry isopropyl alcohol. Window cleaner like
Windex may streak the lens if not followed by alcohol. The
newer butyl alcohol "streak-free" cleaners are better.
While ammonia is alkaline and strong alkalies can
dissolve some kinds of glass there is no real danger from
the very dilte ammonia in Windex and similar cleaners.
If you use acetone be careful of the edge paint, if any,
and of the paint on the cell because it will dissolve
both.
I do not recommend cleaning inside elements when in a
shutter because there is too much danger of getting the
cleaning fluid into the shutter, take the cell out.

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


I'm not absolutely certain about the Geronar formula. It is
reported
to be a Tessar.
That said, the rear should be a single piece of glass. But
it is not.
If it is a cemented piece, then it is not a true Tessar and
the
fogging may be in the cement.
That would be bad.
I've not found the formula out there to describe the lens.
In the mean time I've been searching for a replacement rear
cell.

I think you mis-typed, a Tessar _does_ have a cemented
rear component, a Triplet does not. I also don't remember
what a Geronar is but think it may be a Dialyte. Have to
look it up. If it is a Dialyte its a four element air spaced
lens. Both front and rear cells will have two lenses with an
air space between. There should be a back cap on both cells
allowing access to the inner surfaces.
If its actually a Tessary type and there is haze inside
the rear component its due to the cement being damaged. Most
old lenses were cemented with Canada Balsam. This has good
optical properties but is subject to damage from low
temperatures, which will make it milky. It also tends to dry
out at the edges unless very well sealed, so that its common
for CB cemented lenses to show a yellow ring of oxidation at
the edge. If this goes on long enough the cement at the
edges may crystalize. While a small amount of oxidation at
the edge (its not true separation) does little harm it can
cause problems if it progresses far enough. Most of these
lenses can be recemented. Modern cements are synthetic,
either binary cements similar to common epoxy or UV curing
cements. Some lenses built in about the 1950s have an
earlier synthetic cement of a type cured by heat. Some of
these show degradation or true separation due to problems in
the cementing process. I've seen a number of Kodak lenses
that seemed slightly hazy but on close examination with a
magnifier and correct light, it was evident that the cement
layer had become reticulated, having a sort of orange-peel
look. Some Zeiss lenses and some Wollendak lenses from this
period have actual large bubbles in the cement where it has
completely separated from the glass. All these can be
recemented if they are thought valuable enough. One can try
it at home using a makeshift method of centering but any
valuable lens should be submitted to someone like John van
Stelten who has the proper equipment to do it the right way.


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



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




 




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