B&L Metrogon

FYI
From Surplus Shed:

Metrogon lenses are a 4 element design with very strong curved meniscus
lens elements covering around a 90 degree field. They are used in aerial
cameras for very large format film for the preparation of topographic
maps and for large format projection systems.

The 6 inch focal length lens covers at least a 9" x 9" format at f/6.3.
We know this lens has a 6 inch focal length, but we do not know what the
f number is and we don't have the equipment to accurately determine the
f ratio or the actual maximum format for this lens. Our understanding is
that as the center aperture is made smaller (larger f number), the
coverage format becomes larger. We haven't yet taken one apart, so don't
know if it will be easy or hard to change the center stop. We did some
testing and it looks like this one gives about an 8" x 8" format as is.
There is a small screw on top of the assembly that loosens it and the
barrel slides out. It's a compact 2" long by 2-1/16" diameter.

Metrogon lenses are the most extreme type of symmetrical construction.
Each side of the lens has two elements which provides correction for
color and spherical faults. We are told that the lenses are also
completely free of distortion. Made by Bausch & Lomb. Coated optics.
Great condition. Front and rear elements are 45mm diameter. Focal length
is 152mm. Barrel is 60mm diameter by 50mm long. Mounting 140mm long by
85mm wide with 4 mounting holes. We don't find these very often these days.

Item No: L3392
Price: $28.50

Regards,

Marv

"Marv Soloff" wrote in message
...

The 6 inch focal length lens covers at least a 9" x 9" format at f/6.3.

True.

[...] We haven't yet taken one apart, so don't know if it will be easy or
hard to change the center stop.

I have disassembled one. It is a dead-simple lens. See my earlier post. It
is clear than one can add an aperture using a conventional shutter (with a
lot of machining talent) or using the shutter I showed with an additional
fixed stop at the shutter.