The QC guy went to lunch with the inventor (small world!) whose son had
received my 'hunch' letter. I say hunch because I looked up the name of the
inventor in an online phone directory in the city where the inventor lived.
His son was the recipient of the letter, passed it to Dad, who passed it to
the QC guy over lunch.
The QC guy had accidentally and embarrassedly deleted my email request but
gladly replied.
It is a monochromatic lens...
Here's his cut & pasted reply.
It was used by Opti-Copy on the
"Imposer" camera which was designed to take color seperation negatives or
reflective black and white copy and project them onto a film mounted on an
x-y stepping table in order to make one piece imposed film flats ready to be
contacted onto plates for printing. The lens was very flat field and of the
highest resolution - we were able to reproduce a 150 line screen within +/-
1% dot value over a 15" x 21" image. The model that you have is an 8 element
lens, I have no idea where any drawings of the lens design went to after
Opti-Copy closed, so I can't help you on that. The lens was highly corrected
for 1:1 reproduction, but did a good job from 25% to 150% ratios if stopped
down to F:13.5 ( at 1:1 the "sweet spot" of the lens was F:9.5). This may
seem a little odd that the lens would be used at 1:1 to copy when other
"Step and Repeat" competitors (such as Meisomex or Dai Nippon Screen) would
contact print the negative to the plate, but projection was much faster as
time to load and expose each film was much shorter. Originally we used a 19"
Goertz or Schneider Apo Artar on the Imposer but in the early 80's had this
lens designed. It was first a 23" focal length but later we redesigned at
27" focal length. These lenses cost us about $13,000 per copy when ordered
in groups of 10 and we probably made over 500 imposers to use this lens.
Now for the bad news - Although the lens is very good at what it was
designed for, it is not a color corrected lens. In other words it was
designed for very high resolution using monochromatic light. I forget the
exact wavelengths it was designed to transmit, but it was in the green to
yellow wavelength as we were using film that was not sensitive to red
safelights. I did a test with one of these lenses and focused an image using
green light, then blue light and finally red light to project and found that
the focus distance would shift by almost a half inch at 1:1. I wanted to see
how the lens would preform at higher magnifications so I tested one on a
different camera we made that was designed for enlarging (this camera had an
overhead track 36' long and could project a 12 x 18 film using condensor and
point source light onto a 70" x 14' wide copyboard). At 8x magnifacation the
image was best described as "Mush" even using green light. These lenses
were like this, very good at what they were designed to do, but outside of
that were pretty useless. Sad to say, but the lens will probably not work
for your use.
I tested quite a few lenses while working for Opti-Copy and from the
information you supplied about making experimental large format cameras
would probably suggest using older Apochromatic process lenses of 450mm
focal length and longer for your use. These are names like Apo-Artar,
Apo-Ronar and the like. Most will be f:9 or f:11 four element symetrical
lenses and all will be optimised at 1:1 but do a fairly good job when
stopped down to f:22 when used at high magnifications (Stop down further and
diffraction will cause the image to soften). Remember that these lenses will
cover a much larger area at 1:1 than say at 10x or infinity focus.
Occasionally there will be a 47.5 inch "Red-Dot" Artar come up on e-bay
which would easily cover 18 x 20 at infinity. There are a few "wide angle" 6
element lenses of this type but 360mm seems to be the high focal length for
this style. Enlarger lenses such as Schneider Componon-S or Rodenstock
Rodagon-G were also made only to 360mm lengths and would only cover 8x10 or
streching it a little would cover 11 x 14. Of the Apo style symetrical
lenses, one of the better performers that I tested was the Apo-Germinar
which was a 6 element lens made by Jena - the East German factory of Zeiss.
These seemed to preform better at magnification than the others and are
often seen on e-bay also.
I hope it's good for something...
You guys told me so....
Murray
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