From: nitram@tellabs.com (Marty Hewes)
Subject: Aero lens info needed.
Keywords: Lens, big, heavy
Organization: Tellabs, Inc.
Date: Thu, 8 Oct 1992 22:03:34 GMT


I am looking for information on the latest odd lens I picked up
at a camera show.

I will describe it as "front half" and "back half" of the assembly,
as I wouldn't be a bit surprised if the back half was added later.

The front half consists of a "Kodak Aero Ektar 7" f2.5".  It looks
alot like a press or view camera lens on steroids.  It has an
aperture scale of f2.5 to f16.  The front element is about 3 inches
across.  It is not telephoto, as it focuses a large image circle
onto a film plane at around 7" from the diaphragm.

It's big, heavy, made of brass and metal, painted black, and has no
shutter.  It has a screw on sun shade, and no apparent facilities for
mounting a filter.  It appears to be an asymmetrical design with the
rear element slightly smaller than the front, and noticably flatter
(longer focal length). 

Disassembling the sets of elements from the diaphragm, both of the
elements facing the diaphragm are concave and of small radius, with 
the front one being noticably smaller radius.  Looking through the
front group of elements, I can see four reflections coming back at me,
implying two elements or cemented groups?  The reflections are pretty
bright, one pair white, one pair slight yellow tint.  The glass has 
a few minor bubbles in it.

Looking through the rear set, I think I see six reflections.  It looks
like two blue, two amber, and two white.

It appears that the front set has a focal length near 12 inches while 
the rear set has a focal length closer to eight.

Now for the back half.  The back half is nothing more than a large
helical focusing mount that adapts the lens assembly to a 35mm Pentax
screw mount camera.  I have mounted it, it focusses properly, and
looks pretty good through the finder.  It appears to be all steel,
painted black, with a slightly roughly finished hand machined square
pad mounted to it for tripod mounting.

My guess is that the lens was made for aerial reconnaissance
for the U.S. during World War II.  After the war, I would guess that 
someone bought up surplus Aero lenses and made adapters to mount 
them on popular cameras.

Anybody know better?

Does anybody know the relative strengths and weaknesses of this 
lens?.

At 180mm at f2.5, I would love to have a mount made up to put this
thing on my Mamiya 645.  I can't imagine shooting 4x5 at f2.5.
I suppose if you were thousands of feet up shooting straight 
down, you wouldn't worry too much about focus or depth of field.

Thanks in advance for any info you can provide.

Oh yea, in case anybody is interested, I picked it up for $40.


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