question about Schneider-Kreuznach lens

wrote in message
...
hi,

I've got a Schneider-Kreuznach lens, Symmar 1: 5, 6/210, 1: 12/370

on my 4x5 camera. I know it's a standard 210mm lens, but what
does the 1: 12/370 part mean?


The Symmar is a (nearly) symmetrical design with both the individual cells
(in front of and behind the shutter) capable of forming an image, and the
two together cancelling out (well, nearly) many of the aberrations. A 'side
effect' of the symmetrical design is that it is also a "convertible" lens.

This means that you can remove one of the cells and use just the other as a
lens of somewhat reduced quality but longer focal length. In the case of
the Symmar design the results when 'converted' are better with just the rear
cell than with just the front one, and you will find that the front cell
unscrews from the shutter with a sturdier screw-thread than on most lenses,
precisely because it is designed to be removed and replaced in this way.
(You can remove the rear cell instead and get almost the same focal length
as with the front cell removed, but at slightly less bellows draw.) Symmars
in their original shutters normally have a second set of aperture markings
on the shutter for use when converted, and these are normally marked in
green, matching the green designation on the front ring of the lens.

With the 210mm f5.6, the converted focal length is 370mm, with a maximum
aperture of f12 - hence the markings you see. There should be a second
aperture scale that starts at f12 too, but if not you can ask here and
someone will tell you how to find where to mark the scale.

I have this lens too, and at 210mm it is very good. Converted it is less
so, but still very useable, and the converted lens is not a bad thing for
portraits.



Peter

hi,

I've got a Schneider-Kreuznach lens, Symmar 1: 5, 6/210, 1: 12/370

on my 4x5 camera. I know it's a standard 210mm lens, but what
does the 1: 12/370 part mean?

thanks,

tracy

The lens is a convertable lens. If you remove the front element it bcomes a
F12 370mm lens.
PCR
wrote in message
...
hi,

I've got a Schneider-Kreuznach lens, Symmar 1: 5, 6/210, 1: 12/370

on my 4x5 camera. I know it's a standard 210mm lens, but what
does the 1: 12/370 part mean?

thanks,

tracy

On Tue, 12 Sep 2006 20:52:21 -0400, "PCR" wrote:

The lens is a convertable lens. If you remove the front element it bcomes a
F12 370mm lens.

Thank you very much.

tracy

On Wed, 13 Sep 2006 01:04:23 +0100, "Bandicoot"
wrote:

The Symmar is a (nearly) symmetrical design with both the individual cells
(in front of and behind the shutter) capable of forming an image, and the
two together cancelling out (well, nearly) many of the aberrations. A 'side
effect' of the symmetrical design is that it is also a "convertible" lens.

This means that you can remove one of the cells and use just the other as a
lens of somewhat reduced quality but longer focal length. In the case of
the Symmar design the results when 'converted' are better with just the rear
cell than with just the front one, and you will find that the front cell
unscrews from the shutter with a sturdier screw-thread than on most lenses,
precisely because it is designed to be removed and replaced in this way.
(You can remove the rear cell instead and get almost the same focal length
as with the front cell removed, but at slightly less bellows draw.) Symmars
in their original shutters normally have a second set of aperture markings
on the shutter for use when converted, and these are normally marked in
green, matching the green designation on the front ring of the lens.

I checked it, and it does have the 1: 12/370 in green, but not the
second set of markings, It has one gray or silver set on the top,
going from 6.8 to 64, and from 400 to T (the T is green), and on the
bottom the aperture & F-stop markings are also in gray or silver, and
go in reverse order: T to 400, and 64 to 6.8.

Is the set on the bottom for the converted lens?


With the 210mm f5.6, the converted focal length is 370mm, with a maximum
aperture of f12 - hence the markings you see. There should be a second
aperture scale that starts at f12 too, but if not you can ask here and
someone will tell you how to find where to mark the scale.

I have this lens too, and at 210mm it is very good. Converted it is less
so, but still very useable, and the converted lens is not a bad thing for
portraits.


Thank you very much,

Tracy

PS I took a lcass but haven't used this camera in a while.

spake thus:

I checked it, and it does have the 1: 12/370 in green, but not the
second set of markings, It has one gray or silver set on the top,
going from 6.8 to 64, and from 400 to T (the T is green), and on the
bottom the aperture & F-stop markings are also in gray or silver, and
go in reverse order: T to 400, and 64 to 6.8.

Is the set on the bottom for the converted lens?

No, because it's the same as the one on the top (6.8 - 64). You need a
scale that goes from 12 to ?? (probably 64, maybe 128). By the way, the
T-400 scale is for the shutter.


--
Napoleon won the battle of Waterloo. The German Wehrmacht won World War
II. The United States won in Vietnam, and the Soviets in Afghanistan.
The Zealots won against the Romans, and Ehud Olmert won the Second
Lebanon War.

- Uri Avnery, Israeli peace activist
(http://counterpunch.org/avnery09022006.html)

wrote:
On Wed, 13 Sep 2006 01:04:23 +0100, "Bandicoot"
wrote:

The Symmar is a (nearly) symmetrical design with both the individual cells
(in front of and behind the shutter) capable of forming an image, and the
two together cancelling out (well, nearly) many of the aberrations. A 'side
effect' of the symmetrical design is that it is also a "convertible" lens.

This means that you can remove one of the cells and use just the other as a
lens of somewhat reduced quality but longer focal length. In the case of
the Symmar design the results when 'converted' are better with just the rear
cell than with just the front one, and you will find that the front cell
unscrews from the shutter with a sturdier screw-thread than on most lenses,
precisely because it is designed to be removed and replaced in this way.
(You can remove the rear cell instead and get almost the same focal length
as with the front cell removed, but at slightly less bellows draw.) Symmars
in their original shutters normally have a second set of aperture markings
on the shutter for use when converted, and these are normally marked in
green, matching the green designation on the front ring of the lens.

I checked it, and it does have the 1: 12/370 in green, but not the
second set of markings, It has one gray or silver set on the top,
going from 6.8 to 64, and from 400 to T (the T is green), and on the
bottom the aperture & F-stop markings are also in gray or silver, and
go in reverse order: T to 400, and 64 to 6.8.

Is the set on the bottom for the converted lens?


With the 210mm f5.6, the converted focal length is 370mm, with a maximum
aperture of f12 - hence the markings you see. There should be a second
aperture scale that starts at f12 too, but if not you can ask here and
someone will tell you how to find where to mark the scale.

I have this lens too, and at 210mm it is very good. Converted it is less
so, but still very useable, and the converted lens is not a bad thing for
portraits.


Thank you very much,

Tracy

PS I took a lcass but haven't used this camera in a while.

Hmm. You have a lens whose maximum aperture is f/5.6 in a shutter
whose aperture scale starts at f/6.8. Your lens cells have been moved
from the shutter they were originally delivered in into another
shutter. You might want to have the shutter's aperture scale replaced
with one that's right for your 210/5.6.

intersting.,..never knew that the lens is 2 part and can change to
magnify more.

Isn't this regarded as one of the sharpest lens'?

"2Capture" wrote in message
oups.com...
intersting.,..never knew that the lens is 2 part and can
change to
magnify more.

Isn't this regarded as one of the sharpest lens'?

Its a very good lens but the convertible feature required
some compromise in design. The later version was not made to
be convertible and has somewhat better correction. However,
many lenses can be used as "convertibles" provided the cells
will form an image. Symmars, Dagors, Convertible Protars,
are all essentially double meniscus lenses and either side
may be used alone. The image quality is not as good as the
combined lens and coverage is less.
The Zeiss Convertible Protar, and to some degree the
Convertible Symmar, have each cell corrected for coma, Dagor
cells do not. In a combined lens this aberration is
corrected by the symmetry. Coma causes spots of light to
become blured in a tear-drop shape away from the center of
the image. It is reduced by stopping the lens down. Dagor
cells don't get acceptably sharp at the corners until about
f/45. A Convertible Protar or Symmar will be sharp at
somewhat larger stops.
Convertible lenses were very popular in the days when
most LF images were contact printed because they are
economical. Some were sold in sets, for instance, the Zeiss
Convertible Protar (also made by Bausch & Lomb) was sold in
sets of up to four cells of different focal lengths which
could be used individually or in groups for a variety of
focal lengths.


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

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

"2Capture" wrote in message
oups.com...
intersting.,..never knew that the lens is 2 part and can change to
magnify more.

Isn't this regarded as one of the sharpest lens'?

Its a very good lens but the convertible feature required some
compromise in design. The later version was not made to be convertible and
has somewhat better correction. However, many lenses can be used as
"convertibles" provided the cells will form an image. Symmars, Dagors,
Convertible Protars, are all essentially double meniscus lenses and either
side may be used alone. The image quality is not as good as the combined
lens and coverage is less.
The Zeiss Convertible Protar, and to some degree the Convertible Symmar,
have each cell corrected for coma, Dagor cells do not. In a combined lens
this aberration is corrected by the symmetry. Coma causes spots of light
to become blured in a tear-drop shape away from the center of the image.
It is reduced by stopping the lens down. Dagor cells don't get acceptably
sharp at the corners until about f/45. A Convertible Protar or Symmar will
be sharp at somewhat larger stops.
Convertible lenses were very popular in the days when most LF images
were contact printed because they are economical. Some were sold in sets,
for instance, the Zeiss Convertible Protar (also made by Bausch & Lomb)
was sold in sets of up to four cells of different focal lengths which
could be used individually or in groups for a variety of focal lengths.


And Cooke has brought back the Series XV with the XVa.
http://tinyurl.com/hq9w3 (goes to Cooke Optics website)