[LargeFormat] funky plasmat

[Richard Knoppow]

----- Original Message ----- 
From: "LNphoto" <LNphoto@twmi.rr.com>
To: "f32" <largeformat@f32.net>
Sent: Sunday, October 12, 2003 1:38 PM
Subject: [LargeFormat] funky plasmat


> Since the LS is slow I 'd thought I'd throw this out to
whoever was out
> there.
>
> I was bottom feeding on ebay when I came across this
>
> http://home.twmi.rr.com/lnphoto/plasmat.jpg
>
>
> Now it came with a camera, which was worth the auction, so
I'm not
> expecting much from this lens
>
> but can anybody have a reasonable explanation why it looks
like both
> cells are attached to the front?
> Does anybody have any references about Plasmats?
>
>  From searching post auctions I found (a much better) 9
7/8"  14 1/4"
> set.   Well the back cell looks like it might say 14"
>
> but I can't make out the front.
>
> I fear that the front cell is no more than the rim, but
can't see any
> evidence of it.
>
> Les
>
>
  I also find the photo puzzling. Its hard to read the
printing on the "rims". One looks like it may say Ross on
it. Ross built lenses under license from Zeiss so its
possible they built them for Meyer also
  The Plasmat was derived from the Dagor by air spacing the
inner elements. This gives the designer an additional
surface and a "bending" to work with. The Dagor has an
inherent problem with excessive zonal spherical aberration,
this is the cause of the familiar focus shift. By air
spacing the inner lens its possible to greatly reduce the
zonal. The Plasmat is also capable of very low astigmatism.
I don't know the quality of the original Plasmats but the
generic type has become the standard for most modern large
format camera lenses, copy lenses, and nearly all enlarging
lenses. It was not too popular at the time of its invention
because the additional surfaces increse the flare so the
type had to await the availability of good anti-reflection
coating for its virtues to be recognized and applied.
  Hugo Meyer sold Plasmats in sets but the mountings were
conventional. I can't make sense of the double looking rim
either.
  The Plasmat was designed by Paul Rudolph, the inventor of
the Tessar, Protar, and other lenses. Kingslake says he lost
his fortune because of WW-1 and had to come out of
retirement. He prefered to work for a smaller company than
Zeiss so joined Meyer. He designed the Plasmat and some
other related lenses for them. From what Kinglslake says
some of these designs may not have been too good. The name
Plasmat suggests a "plastic" image, that is one with some
softness, so, while the Plasmat type is capable of extremely
good correction its possible that Rudolph's design did not
achieve this potential.
  We will be awaiting with 'bated breath to learn what this
actually turns out to be.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@ix.netcom.com