View Full Version : Question on convertible Symmars

Joe Smigiel
16-Jan-2015, 21:07
There's a thread over on APUG about remounting convertible Symmars from Sinar DB mounts into shutters. After reading through it, I posted a question in that thread that I'll repeat here:

When remounting a Plasmat like a Symmar, is the spacing between front and rear groups critical? I imagine there is an optimum spacing, but I also suspect remounting DB lens groups into a modern shutter that has the same threads would give acceptable results. For that matter, if one had a number of convertible Symmar cells of different focal lengths that fit the same shutter, wouldn't a casket set of sorts be possible from the various groups? I think the 150mm,180mm & 210mm all fit a modern #1 shutter, and the 240mm, 300mm & 360mm fit a #3, while the 80mm, 100mm, and 135mm fit a #0.

Anyone mixed and matched them?

I'm curious if it is practical even though perhaps not optimal. For that matter, couldn't later Symmars (Symmar-S series for example) marketed without the "convertible" designation also be used as single groups or mixed focal length groups, maybe even with older element groups?

Dan Fromm
17-Jan-2015, 07:49
Joe, some years ago I measured some Copal Polaroid Press #1 shutters and found to my horror that the tube lengths were a little longer than the #1 standard. I had a 6/4 plasmat -- not a jes' plain Symmar -- that I wanted to put in one, so asked my friend Eric Beltrando (visit his site www.dioptrique.info) what his ray tracing program thought. He said that plasmats aren't particularly sensitive to spacing errors and that an error of the magnitude I was thinking of making (< 1% of focal length) should have no effect on my images.

As for making casket sets containing Symmar or, for that matter, G-Claron, cells, its been done. Jim Galli is a strong advocate of doing this with dagor type G-Clarons. Two problems. Shutter sizes limit which cells can be used. Small gains from combinations that are physically possible, for example, half of a 100 plus half of a 135 equals something around 120.

Berthiot used to sell casket sets based on Eurygraphe cells. Dagor type. I can't paste the page in here, but if you'll go to http://cnum.cnam.fr/CGI/redire.cgi?M11121 , click on EXPORTS, click on PDF and go to p. 33 you can see what they offered before they started cutting back.

17-Jan-2015, 08:17
Schneider sold a sort of casket set of Symmars for a short time. I had a quick look but can't remember what year they advertised them. I think I scanned an advert for a similar thread a few years ago. It was around the same time their adverts and data listed the 90mm f6.8 Angulon as convertible lenses.


Len Middleton
17-Jan-2015, 08:17

I find the casket set concept intriguing, but looking at the relative recent offering from Wisner with his plasmat set for 8x10, found the combination limited, and a drop in performance when used as a single element.

With the current Wisner 8x10 set offering on feeBay, of lens elements 350, 400, 500, & 600mm, that represents a maximum range of combined units of 227mm to 333mm. According to the Wisner catalogue, combined performance is coverage of 80 deg and resolution of 60 lines/mm @ f22. A single element performance drops to 30 deg and 45 to 50 lpmm @f32 to 45.

It seems like a lot of effort for relatively short steps in focal length, that could easily be covered with complete lens assemblies. I can see value if travelling light in eliminating the weight and weight (plus cost) of multiple shutters. There is of course the additional risk to the lens elements in transport. and installing and removing them in he shutter while in the field

Will be interested in what you find out.



Oren Grad
17-Jan-2015, 10:03
It's going to be a pain to find it with the search engine, but we've had a bit of discussion here over the years on using newer plasmats, particularly the Symmar-S, as convertibles. My vague recollection is that it's certainly physically possible but the performance losses relative to using the FLs as intended get greater with each new generation. Also, the usual caveats apply about risks of swapping cells on the fly, losing shims, etc. Mixing cells across generations is likely to be more problematic - the optical designs did change.

17-Jan-2015, 21:00
I think the 135/235 is in a 1 not a 0. I accumulated a collection of the convertible symmars to make a travel casket set. Never got around to figuring out the FL combinations or trying it out.


18-Jan-2015, 03:17
I think the 135/235 is in a 1 not a 0. I accumulated a collection of the convertible symmars to make a travel casket set. Never got around to figuring out the FL combinations or trying it out.


The 135mm Symmar & the S have always been in a #0 shutter, they are quite small lenses.


Mark Sampson
18-Jan-2015, 20:30
Perhaps the Wisner casket set was not a sales success because the (apparently limited) flexibility it offered wasn't worth the price. I wonder how many were actually made/sold?