Metrogon cell spacing revisited HELP

I know there are some folks who will howl about 'why bother' or worse.
Whatever... Most of you are busy shooting film, so don't waste your
time griping about this. I posted this in the hopes it will be of use,
as well as helping me figure out the best spacing, and I would like to
properly interpret some apparent discrepancies.

Street wisdom on Metrogon cell spacing for barrel or other use is as
follows.

"0.2 inches for 6" cells"
"0.287 inches for 12" cells". Second wisdom 'pearl is 1.365" between
flanges.




I always assumed the 0.2 and 0.287 meant back flange spacing, so
I took measurements to see if it matches & to contemplate significance
of this relative to a 12" Metro cell set I just got, but have no
shutter body to measure.

I have a 6" set of Metrogon and 6" Eastman Kodak Topogon cells, both in
K17 variants.

I realized I had a B&L and Kodak cell combined when I took
measurements, so that is not reported here until I repeat it.

I just did the 12" cell pair tonight. Something doesn't add up.

I used a calibrated digital depth micrometer and stand at work with
0.0001" resolution and gauge blocks so I believe my measurements. I
rounded to 0.0005" because I had some 'tilt' showing up one one
surface. I suspect it's because I'm measuring relative to a surface
that doesn't need to be precision. (I had to balance each cell on
blocks because the glass protrudes further in front than the flanges.

12" front cell of 303.25 mm set aluminum rear flange protrudes 0.5828"
(let's say 0.5825") beyond the back-of-cell mounting surface (into the
shutter body cavity direction).

12" matched rear cell is marked FD 10.954" and protrudes 0.4828" (let's
say 0.4825") beyond the back-of-cell mounting surface.

0.5825+0.4825 = 1.065" = total cell metal protrusion into barrel or
shutter.

Reported flange spacing of 1.365" leaves 0.300" difference. Urban
legend says 0.287" "between cells", and I have make assumptions about
what that means.

So, I see two interesting differences. 0.1000" depth difference between
front and rear cells, and a 0.013" difference which is significant in
optics but how does one put that into perspective?

Many say the Metrogon is symmetrical, but I believe the patent says it
is not, actually 5-element (including one glass plate) vs 4 element for
Topogon. This may explain the difference. I believe for the 6" both
Metrogon and Topogon conform to same MIL/Camera spec and are
interchangeable in K17 shutters.

Metrogon has lower distortion than Topogon. Maybe the 5th element
achieved a required focal position shift to maintain
retro-compatibility and interchangeability with existing shutter/camera
specs.

I also took flange to iris and flange to shutter measurements on the 6"
shutter to see if iris or shutter leaf spacing was centered.

It would be interesting if anyone can comment on iris position, spacing
etc. for shorter infinity distances than 19.8 km! (That is, is there a
better setup for terrestrial work like landscapes and architecture.

My 12" cell set came with with B&L's resolution test data. Kind of like
a lens Dead Sea Scroll of sorts.

Thanks

Murray

I have the prescription for the Metrogon and will post it to you
when I get home tomorrow.
The Topogon is a Zeiss design. I didn't know that Kodak made a lens
using this name. It may or may not be the same as the Zeiss lens.
The distortion of the Metrogon _is_ less than the Topogon but I am
uncertain if its the additional element that corrects it. The
calculated performance of the Metrogon is generally superior to the
Topogon. Kodak had an outstanding optical department during the days it
was run by Rudolf Kingslake so I suspect they had their own version of
the Topogon with perhaps better performance than the original Zeiss
version.

--
Richard Knoppow

I have the prescription for the Metrogon and will post it to you
when I get home tomorrow.
The Topogon is a Zeiss design. I didn't know that Kodak made a lens
using this name. It may or may not be the same as the Zeiss lens.
The distortion of the Metrogon _is_ less than the Topogon but I am
uncertain if its the additional element that corrects it. The
calculated performance of the Metrogon is generally superior to the
Topogon. Kodak had an outstanding optical department during the days it
was run by Rudolf Kingslake so I suspect they had their own version of
the Topogon with perhaps better performance than the original Zeiss
version.

--
Richard Knoppow

OK- thanks.

1) I'm a few steps short of understanding how to scale a lens
prescription from that given in , for example a patent, to another f.l.

2) I assumed I shouldn't scale measurements from a 6" shutter body to
the 12" flange spacing requirement (not having one to meaure) because
with the larger format, there might be other issues than just scaling.
The 0.2 and 0.287 numbers didn't imply any such linear scaling either.

3) I call the Eastman Kodak (RR s/n, 1955) one a Topogon because it has
the Zeiss aerial lens patent number on the front. I was trying to
conspicuously distinguish from the assumption it was merely a Kodak
version of a Metrogon. It does conspicuously say Eastman Kodak and not
Aero-Ektar. I suppose having a patent number on it doesn't mean it
conforms exactly to that patent but uses enough of it to require
acknowledgement,royalties, whatever. I would guess it would be odd for
Kodak to have their own 'orphan' aerial design that worked in the K-17
shutter/camera series. It doesn't actually say Topogon on it. GEH was
unfamiliar with it, but I only get accurate answers from them when a
regular staffer replies. I wonder if the non-helpful answers came from
student interns :O).

Oh, I haven't looked at any of the Metrogon-like patents lately, so I
don't remember if the Zeiss one actually uses the Topogon name in the
patent, or if I got that from web descriptions.


I remember thinking the 6" lens was kind of 'beady-eyed' when I first
got it, but the 12" is astonishing to look at, at least for me, even
more so than the 309 or 610 mm A-E lenses.

Thanks

Murray

OK- thanks.

1) I'm a few steps short of understanding how to scale a lens
prescription from that given in , for example a patent, to another f.l.

2) I assumed I shouldn't scale measurements from a 6" shutter body to
the 12" flange spacing requirement (not having one to meaure) because
with the larger format, there might be other issues than just scaling.
The 0.2 and 0.287 numbers didn't imply any such linear scaling either.

3) I call the Eastman Kodak (RR s/n, 1955) one a Topogon because it has
the Zeiss aerial lens patent number on the front. I was trying to
conspicuously distinguish from the assumption it was merely a Kodak
version of a Metrogon. It does conspicuously say Eastman Kodak and not
Aero-Ektar. I suppose having a patent number on it doesn't mean it
conforms exactly to that patent but uses enough of it to require
acknowledgement,royalties, whatever. I would guess it would be odd for
Kodak to have their own 'orphan' aerial design that worked in the K-17
shutter/camera series. It doesn't actually say Topogon on it. GEH was
unfamiliar with it, but I only get accurate answers from them when a
regular staffer replies. I wonder if the non-helpful answers came from
student interns :O).

Oh, I haven't looked at any of the Metrogon-like patents lately, so I
don't remember if the Zeiss one actually uses the Topogon name in the
patent, or if I got that from web descriptions.


I remember thinking the 6" lens was kind of 'beady-eyed' when I first
got it, but the 12" is astonishing to look at, at least for me, even
more so than the 309 or 610 mm A-E lenses.

Thanks

Murray

In article .com,
Richard Knoppow wrote:

The distortion of the Metrogon _is_ less than the Topogon but I am
uncertain if its the additional element that corrects it. The
calculated performance of the Metrogon is generally superior to the
Topogon. Kodak had an outstanding optical department during the days it
was run by Rudolf Kingslake so I suspect they had their own version of
the Topogon with perhaps better performance than the original Zeiss
version.

I believe, but cannot prove, that there were members of the Aero-Ektar
family with different designs than the common Xenotar-like design we
know from the radioactive 7" lens, presumably meant for different
purposes. I have seen one Aero-Ektar that was quite physically wide
and had a steep curve to its front element, very Metrogon-like; I wonder
if it was a mapping lens? I think it was 6" -- I have another 6"
Aero Ektar, however, that does seem to be the same general design as
the famous 7" (it too is a very odd lens: it dates to the 1950s from
its serial number, but it is multicoated).

Unfortunately I think a lot of information on these lenses died with
Kingslake. Are any other members of the 1940s/1950s Kodak design team
still alive?

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to be
abandoned or transcended, there is no problem." - Noam Chomsky

In article .com,
Richard Knoppow wrote:

The distortion of the Metrogon _is_ less than the Topogon but I am
uncertain if its the additional element that corrects it. The
calculated performance of the Metrogon is generally superior to the
Topogon. Kodak had an outstanding optical department during the days it
was run by Rudolf Kingslake so I suspect they had their own version of
the Topogon with perhaps better performance than the original Zeiss
version.

I believe, but cannot prove, that there were members of the Aero-Ektar
family with different designs than the common Xenotar-like design we
know from the radioactive 7" lens, presumably meant for different
purposes. I have seen one Aero-Ektar that was quite physically wide
and had a steep curve to its front element, very Metrogon-like; I wonder
if it was a mapping lens? I think it was 6" -- I have another 6"
Aero Ektar, however, that does seem to be the same general design as
the famous 7" (it too is a very odd lens: it dates to the 1950s from
its serial number, but it is multicoated).

Unfortunately I think a lot of information on these lenses died with
Kingslake. Are any other members of the 1940s/1950s Kodak design team
still alive?

--
Thor Lancelot Simon

"The inconsistency is startling, though admittedly, if consistency is to be
abandoned or transcended, there is no problem." - Noam Chomsky

"Thor Lancelot Simon" wrote in message
...
In article
.com,
Richard Knoppow wrote:

The distortion of the Metrogon _is_ less than the
Topogon but I am
uncertain if its the additional element that corrects it.
The
calculated performance of the Metrogon is generally
superior to the
Topogon. Kodak had an outstanding optical department
during the days it
was run by Rudolf Kingslake so I suspect they had their
own version of
the Topogon with perhaps better performance than the
original Zeiss
version.

I believe, but cannot prove, that there were members of
the Aero-Ektar
family with different designs than the common Xenotar-like
design we
know from the radioactive 7" lens, presumably meant for
different
purposes. I have seen one Aero-Ektar that was quite
physically wide
and had a steep curve to its front element, very
Metrogon-like; I wonder
if it was a mapping lens? I think it was 6" -- I have
another 6"
Aero Ektar, however, that does seem to be the same general
design as
the famous 7" (it too is a very odd lens: it dates to the
1950s from
its serial number, but it is multicoated).

Unfortunately I think a lot of information on these lenses
died with
Kingslake. Are any other members of the 1940s/1950s Kodak
design team
still alive?

--
Thor Lancelot Simon


Kodak certainly made other aerial lenses. The well known
Aero Ektar was designed for night recconaisance using flash
bombs. Its a Biotar type with seven elements. Kodak also
made an earlier Tessar type lens called the Aerostigmat. I
have no specific information on mapping or survey lenses
from Kodak although I am pretty sure they made them.


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

"murrayatuptowngallery"
wrote in message
oups.com...
I know there are some folks who will howl about 'why
bother' or worse.
Whatever... Most of you are busy shooting film, so don't
waste your
time griping about this. I posted this in the hopes it
will be of use,
as well as helping me figure out the best spacing, and I
would like to
properly interpret some apparent discrepancies.

Street wisdom on Metrogon cell spacing for barrel or other
use is as
follows.

"0.2 inches for 6" cells"
"0.287 inches for 12" cells". Second wisdom 'pearl is
1.365" between
flanges.




I always assumed the 0.2 and 0.287 meant back flange
spacing, so
I took measurements to see if it matches & to contemplate
significance
of this relative to a 12" Metro cell set I just got, but
have no
shutter body to measure.

I have a 6" set of Metrogon and 6" Eastman Kodak Topogon
cells, both in
K17 variants.

I realized I had a B&L and Kodak cell combined when I took
measurements, so that is not reported here until I repeat
it.

I just did the 12" cell pair tonight. Something doesn't
add up.

I used a calibrated digital depth micrometer and stand at
work with
0.0001" resolution and gauge blocks so I believe my
measurements. I
rounded to 0.0005" because I had some 'tilt' showing up
one one
surface. I suspect it's because I'm measuring relative to
a surface
that doesn't need to be precision. (I had to balance each
cell on
blocks because the glass protrudes further in front than
the flanges.

12" front cell of 303.25 mm set aluminum rear flange
protrudes 0.5828"
(let's say 0.5825") beyond the back-of-cell mounting
surface (into the
shutter body cavity direction).

12" matched rear cell is marked FD 10.954" and protrudes
0.4828" (let's
say 0.4825") beyond the back-of-cell mounting surface.

0.5825+0.4825 = 1.065" = total cell metal protrusion into
barrel or
shutter.

Reported flange spacing of 1.365" leaves 0.300"
difference. Urban
legend says 0.287" "between cells", and I have make
assumptions about
what that means.

So, I see two interesting differences. 0.1000" depth
difference between
front and rear cells, and a 0.013" difference which is
significant in
optics but how does one put that into perspective?

Many say the Metrogon is symmetrical, but I believe the
patent says it
is not, actually 5-element (including one glass plate) vs
4 element for
Topogon. This may explain the difference. I believe for
the 6" both
Metrogon and Topogon conform to same MIL/Camera spec and
are
interchangeable in K17 shutters.

Metrogon has lower distortion than Topogon. Maybe the 5th
element
achieved a required focal position shift to maintain
retro-compatibility and interchangeability with existing
shutter/camera
specs.

I also took flange to iris and flange to shutter
measurements on the 6"
shutter to see if iris or shutter leaf spacing was
centered.

It would be interesting if anyone can comment on iris
position, spacing
etc. for shorter infinity distances than 19.8 km! (That
is, is there a
better setup for terrestrial work like landscapes and
architecture.

My 12" cell set came with with B&L's resolution test data.
Kind of like
a lens Dead Sea Scroll of sorts.

Thanks

Murray

Lenses scale linearly. Many prescriptions are
standardized at 100mm and dimensions given for that focal
length. For other focal lengths the distances, thicknesses,
radiuses, are simply multiplied or devided by the ratio of
the actual focal length to the nominal FL in the
prescription.

The Topogon was designed by Robert Richter of Zeiss and is
covered in USP 2,031,792
The Metrogon was designed by Wilbur Rayton of B&L and is
covered in USP 2,325,275
Here is the prescription from the patent:


Radius Thickness Index/V No.

OBJ: INFINITY
INFINITY AIR
S1: 16.477175
4.409950 1.61,57.2
S2: 19.764592
0.801809 AIR
S3: 21.147715
1.974455 1.61,57.2
S4: 25.156756
0.952148 AIR
S5: 13.109577
0.691560 1.72,29.3
S6: 10.894580
7.416733 AIR
STO: INFINITY
8.759763 AIR
S8: -10.894580
0.651470 1.72,29.3
S9: -13.169713
1.513415 AIR
S10: -26.399563
7.887796 1.61,57.2
S11: -18.080794
80.028314 AIR
IMG: INFINITY

The spacings and curvatures above are based on a focal
length of 100.0 mm
Spaces are measured from the center of each element to the
center of the next.
For this lens the distance from the center of the front
element to the stop is given as 7.416733mm and from the stop
to the center of the rear lens 8.759763mm so the total
spacing from apex to apex is 16.176496 mm. If you have a 6"
lens, i.e. 152mm, the spacing will be 1.52X the above value
or 24.58827392 mm. For practical purposes this can be
rounded off to 24.6mm. It is convenient to measure the apex
distances from the iris. The thickness of the iris should be
taken into account but it is usually thin enough to be
neglected.

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

"murrayatuptowngallery"
wrote in message
oups.com...
I know there are some folks who will howl about 'why
bother' or worse.
Whatever... Most of you are busy shooting film, so don't
waste your
time griping about this. I posted this in the hopes it
will be of use,
as well as helping me figure out the best spacing, and I
would like to
properly interpret some apparent discrepancies.

Street wisdom on Metrogon cell spacing for barrel or other
use is as
follows.

"0.2 inches for 6" cells"
"0.287 inches for 12" cells". Second wisdom 'pearl is
1.365" between
flanges.




I always assumed the 0.2 and 0.287 meant back flange
spacing, so
I took measurements to see if it matches & to contemplate
significance
of this relative to a 12" Metro cell set I just got, but
have no
shutter body to measure.

I have a 6" set of Metrogon and 6" Eastman Kodak Topogon
cells, both in
K17 variants.

I realized I had a B&L and Kodak cell combined when I took
measurements, so that is not reported here until I repeat
it.

I just did the 12" cell pair tonight. Something doesn't
add up.

I used a calibrated digital depth micrometer and stand at
work with
0.0001" resolution and gauge blocks so I believe my
measurements. I
rounded to 0.0005" because I had some 'tilt' showing up
one one
surface. I suspect it's because I'm measuring relative to
a surface
that doesn't need to be precision. (I had to balance each
cell on
blocks because the glass protrudes further in front than
the flanges.

12" front cell of 303.25 mm set aluminum rear flange
protrudes 0.5828"
(let's say 0.5825") beyond the back-of-cell mounting
surface (into the
shutter body cavity direction).

12" matched rear cell is marked FD 10.954" and protrudes
0.4828" (let's
say 0.4825") beyond the back-of-cell mounting surface.

0.5825+0.4825 = 1.065" = total cell metal protrusion into
barrel or
shutter.

Reported flange spacing of 1.365" leaves 0.300"
difference. Urban
legend says 0.287" "between cells", and I have make
assumptions about
what that means.

So, I see two interesting differences. 0.1000" depth
difference between
front and rear cells, and a 0.013" difference which is
significant in
optics but how does one put that into perspective?

Many say the Metrogon is symmetrical, but I believe the
patent says it
is not, actually 5-element (including one glass plate) vs
4 element for
Topogon. This may explain the difference. I believe for
the 6" both
Metrogon and Topogon conform to same MIL/Camera spec and
are
interchangeable in K17 shutters.

Metrogon has lower distortion than Topogon. Maybe the 5th
element
achieved a required focal position shift to maintain
retro-compatibility and interchangeability with existing
shutter/camera
specs.

I also took flange to iris and flange to shutter
measurements on the 6"
shutter to see if iris or shutter leaf spacing was
centered.

It would be interesting if anyone can comment on iris
position, spacing
etc. for shorter infinity distances than 19.8 km! (That
is, is there a
better setup for terrestrial work like landscapes and
architecture.

My 12" cell set came with with B&L's resolution test data.
Kind of like
a lens Dead Sea Scroll of sorts.

Thanks

Murray

Lenses scale linearly. Many prescriptions are
standardized at 100mm and dimensions given for that focal
length. For other focal lengths the distances, thicknesses,
radiuses, are simply multiplied or devided by the ratio of
the actual focal length to the nominal FL in the
prescription.

The Topogon was designed by Robert Richter of Zeiss and is
covered in USP 2,031,792
The Metrogon was designed by Wilbur Rayton of B&L and is
covered in USP 2,325,275
Here is the prescription from the patent:


Radius Thickness Index/V No.

OBJ: INFINITY
INFINITY AIR
S1: 16.477175
4.409950 1.61,57.2
S2: 19.764592
0.801809 AIR
S3: 21.147715
1.974455 1.61,57.2
S4: 25.156756
0.952148 AIR
S5: 13.109577
0.691560 1.72,29.3
S6: 10.894580
7.416733 AIR
STO: INFINITY
8.759763 AIR
S8: -10.894580
0.651470 1.72,29.3
S9: -13.169713
1.513415 AIR
S10: -26.399563
7.887796 1.61,57.2
S11: -18.080794
80.028314 AIR
IMG: INFINITY

The spacings and curvatures above are based on a focal
length of 100.0 mm
Spaces are measured from the center of each element to the
center of the next.
For this lens the distance from the center of the front
element to the stop is given as 7.416733mm and from the stop
to the center of the rear lens 8.759763mm so the total
spacing from apex to apex is 16.176496 mm. If you have a 6"
lens, i.e. 152mm, the spacing will be 1.52X the above value
or 24.58827392 mm. For practical purposes this can be
rounded off to 24.6mm. It is convenient to measure the apex
distances from the iris. The thickness of the iris should be
taken into account but it is usually thin enough to be
neglected.

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