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Old February 13th 11, 09:22 PM posted to rec.photo.equipment.large-format
Richard Knoppow
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Posts: 751
Default Lens Cell Cleaning

Lots of snipping here................................

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

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 thought a Tessar had four elements, the rearmost was a
cemented doublet.

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That is correct except that it is possible to have a
"reversed" Tessar with the cemented component in the front.
Also, some Tessar types have the iris in the front air space
instead of the rear even though the cemented component is in
the back.
However, the Geronar is a Cooke Triplet, a
three-element, air-apaced lens with no cemented surfaces.
Its of high quality and such lenses are capable of good
performance at moderate stops.


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Richard Knoppow
Los Angeles, CA, USA