[LargeFormat] Whole lot O lenses!

[Richard Knoppow]

----- Original Message ----- 
From: "Craig Koshyk" <craig@prairieview.ca>
To: <largeformat@f32.net>
Sent: Friday, February 06, 2004 7:55 AM
Subject: [LargeFormat] Whole lot O lenses!


>
> Hi All,
>
> I just came across a bucket full of old process lenses at
a local shop.
> The shopkeeper and I are curious about them.
>
> Any info (use, history, current value etc.) anyone could
provide would
> be greatly appreciated.
>
> So here's the list
>
> 1. 19 Inch Goertz Apo Artar (red dot, f11) ( Will this
lens be usefull
> for my 8x20 if I can get it mounted in a shutter?)
>
> 2. Apo Nikkor's:  there is a 900mm,  a 610 mm, a 600mm,
and a 480mm all
> are mounted in devises that look like the came off the
front of a
> process camera.
>
> 3. Goetz Apo Artar 47 1/2 inch (!!) Red Dot Artar f15
(this thing looks
> like something one would lob into a trench during the
first world war)
>
> 4. Goertz Apo Tessar 900mm (another monster howitzer
shell!)
>
>
> Tnanks
>
> Craig Koshyk
>
> Vouloir c'est pouvoir
>
  the Apo Artar and similar lenses have specified coverage
angles of around 48degrees a infinity focus. In practice
this can be stretched to around 55 degrees meaning the lens
will cover an image circle of a diameter about equal to its
focal length. The sharpness does fall off beyond the
catalogue limit. This is characteristic of four element air
spaced lenses of this type. Because process lenses were not
required to cover a wide angle, and because they were used
at near 1:1 where coverage is double that at infinity, they
were corrected for best performance for that rather narrow
coverage. AFAIK, the Apo Nikor is the same generic type.
  8x10 has a diagonal of 21.5 inches. The 19" Artar might
just barely make it but image quality in the corners will
not be good.
  A property of all anastigmat lenses is that they are
corrected for astigmatism at the center and at some other
image height, generally near the limit of coverage. The
ability to cover a wider angle is partly dependant on how
rapidly the two stigmatic fields depart beyond this second
point, which is called the stigmatic node. Dialyte type
lenses, such as the Apo Artar, have a very rapid departure
of the two fields after this point so the image quality
becomes poor very rapidly with increasing angle and stopping
down does not improve it. A Dagor, while not as sharp in the
center, will cover nearly twice the image angle of an Artar.

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