[LargeFormat] Fun with Convertible Lenses

Sun Dec 30 11:35:15 2001

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Fun with Convertible Lenses:

How can a modern large format lens be any fun? You  can not even take it
apart to use it!

Convertible "symmetrical" lenses offer multi-focal lengths to the large
format photographer.

I the early days the lens designers found that if they used similar
shaped glass on both sides of the diaphragm that it solved a lot of
optical problems. So the invented the symmetrical lens.

A popular primitive one was the "Rapid Rectilinear lens".

Later mores sophisticated lenses came out like:

         The Dagor and Turner-Reich

These later lenses are made up of 8 and 10 elements with clear cement
holding two multi-element lenses together. They do not require lens
coating because the designers removed the air-spaces between the
elements.

These lenses were the top work-horses for the large-format commercial
photographer during the first half of the twentieth century. And still
provide beautiful work.

And, as a bonus, they are convertible. That is,they were offered in 2 or
3 focal lengths. When the front and back elements are used separately on
the shutter.

Do you know what a "Casket Set" is?

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<HTML>
<P>                                  
Jay Allen
<p>Come see my <A
HREF="http://home.talkcity.com/EaselSt/clock-doc/index.htm">home
page</A>.
or go to:  escape.to/jays

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