How to convert a Schneider lens?

I have a Schneider symmar 210 5:6 without a shutter. It's an old

one from the end of the sixties. It has got additional markings on

the lens, 1:12 370 in green. This means that it's convertible. So I

check the archives and various articles and they all say the

same thing. To convert it to the longer focal length, remove the

front element. But (and here comes the question) if I unscrew the

front element this leaves the apreture mechanism exposed!

There doesn't seem to be any way of removing any less. Am I

missing something here? Or rather WHAT am I missing?

Please help me

That's right. Take the front element off. Yes it does leave the shutter/aperature

mechanism exposed. Yes this is normal. Be prepared for the lens to be a little softer

than it is when both cells are on. Most people use it for B&W and use a coloured filter

to help minimize chromatic abberation.

I have also a Schneider Symmar - it's the 180/5.6-315/12 - and the same problem. I use it on my Linhof Technika V 6x9 (last model). When i unscrew the front element there is in no bellows extension a sharp image at the GG. But when i unscrew the rear element, i have a very sharp image at all distances. The bellows extension at infinity is circa 280mm. Could'nt be this a hint, that the lens gets her focal length of 315mm when the rear element is unscrewed?

There are two optical reasons for using the rear element, and

two practical reasons for using the front one.

 

First, the single cells of Symmars are themselves asymmetric,

and work best with their concave, inner faces towards the

subject. The other way round you get higher aberrations.

Second, having the stop in front of the cell reduces aberrations

more than if you put it behind the lens. So, optically, the best

arrangement is to have the aperture in front of the cell with the

cell's concave surface facing the subject. This is most easily

done by unscrewing the front element and using the rear one.

 

However, as Joakim pointed out, this leaves the aperture and

shutter exposed to the elements and the photographer's fingers.

It also means you have to extend the bellows further because the

optical centre of the single cell is behind the aperture position. If

you use the front cell, it protects the shutter and you get a free

short extension board so you can use less bellows extension.

The only practical downside is that you have to remove the

lensboard to remove the cell.

 

Play with the lens and its cells to see if the reduction in quality

from using the front cell is worth putting up with. I have 150, 210

and 360 Symmars and almost always take off the front cell so I

don't have to handle the half lens on a loose lensboard. The

only exception is the 360 beast, where the reduced bellows draw

of using the front cell becomes significant.

You don't need to remove the front element for any length of time, only long enough to make the photograph. So leaving the front element exposed for the brief time it takes to make the photograph shouldn't be a problem unless you're photographing in bad weather.

 

I have a different convertible lens and found a noticeable improvement when I placed a yellow filter in front of the aperture. On my lens the threads didn't accept any filter I owned so I just hand-held my largest filter (82mm) in front of the aperture while the photograph was being made. I don't know whether you can do this or not without having a shutter but I think it would be worth a try for the improvement that it seems to make (at least with my lens).

The first time I tried converting a Schneider 180mm Symmar, I removed the front element. The negs I got were terribly unsharp in the corners- no good. Then, many years later, on this forum I learned about the method of using only the rear element group. So I tried again, this time using the rear group only, and photographing the same scene with my 300mm Nikkor-M. The Nikkor was sharper, but the image from the converted Schneider was quite usable (both lenses were at f/32). Live and learn!

joakim

 

check out entry # 12 or 13 ..

 

http://www.schneideroptics.com/info/faq/large_format_lenses/

 

 

-john

Ok, I've got a question now. I have 2 Symmar lenses, a 150/265 and a 210/365. On

my Graphic View using the 210/365 lens there's not enough bellows draw to focus at

infinite when it's 'properly' converted. I can use it when I remove the rear element just

fine, although that does make for a very 'soft' focus. Since I just got the 150/265 and

I can properly convert it, it got me thinking, why can't I mount a filter (like a skylight

1A) in front of the shutter to protect it. So I tried to see if I could find a Series VI

holder with a 40mm thread (to screw into the front of the shutter), but apparently

they're not made/available.

 

I have a series VI slip on adapter that almost fits in the shutter, so I wraped some tape

around it to snug it up, and it works nicely. Then just for the heck of it, I tried putting

a +1 diopter portrait lens in the filter holder, and trying that with the 210/365, and

found with that combo I could in fact focus it on my camera, and the focal length

while no longer 365 was much closer to it than using the front element was (dispite

what folks say, the 2 elements (or groups, or whatever they're called) are NOT the

same, in effect the Symmar lenses are triple convertables)

 

So I guess my question is this: Is there any reason not to use the setup I described?

(using a +1 portrait lens in front of the shutter with the rear group)

Sorry for the long post :(

 

-Mike