Cheesehead wrote:
Cheesehead wrote:
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.
--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey
http://counter.li.org
^^-^^ 12:20:01 up 24 days, 20:55, 3 users, load average: 4.74, 4.81, 4.76
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 thought a Tessar had four elements, the rearmost was a cemented doublet.
--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey
http://counter.li.org
^^-^^ 12:20:01 up 24 days, 20:55, 3 users, load average: 4.74, 4.81, 4.76