[rollei_list] Re: Spinning front taking lens and postings


----- Original Message ----- From: "Jerry Lehrer" <jerryleh@xxxxxxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Wednesday, December 28, 2005 1:00 PM
Subject: [rollei_list] Re: Spinning front taking lens and postings


Ruddy,

You think I am joking about the spinning lens elements?
In fact there was a line of Zeiss(?) lenses that had an
internal component that was deliberately spun by the action
of a pneumatic bulb and rubber air tubing. This was done to
permit uniform exposure an the film. Even Richard can
explain that.

Jerry

This is the Goerz Hypergon. I am not sure Zeiss ever built any Hypergons after merging with Goerz. It is not an eleemnt which spins but rather an external light equalizer. The Hypergon covers a very wide angle, something like 120 degrees. It has tremendous light fall off, even more than the rule-of-thumb cos^4 theta rule. In order to partially equalize the fall off the lens came equipped with a sort of obstructive stop in the form of a propeller shaped obstructive stop fitted to the front of the camera. The stop was spun by an air pump. It was supposed to be used for about 85% of the exposure and fall away for the remainder. Because the Hypergon is not corrected for spherical aberration or chromatic aberration it must be used at very small stops, around f/36 to f/45 so the required exposures were long enough to make this set up practical.
The Hypergon was designed (1900) by Emile von Hoegh, the designer of the Dagor and Celor lenses. It is a simple lens consisting of two very steeply curved, thin, meniscus lenses. The outer surface is nearly spherical. They must have been exceptionally difficult to make.
The later wide angle aerial lenses like the Zeiss Topogon and Bausch & Lomb Metrogon are usually classed as double Gauss lenses, which they are, but are also of the meniscus type and trace their ancestry back to the Hypergon.

---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx


---
Rollei List

- Post to rollei_list@xxxxxxxxxxxxx

- Subscribe at rollei_list-request@xxxxxxxxxxxxx with 'subscribe' in the subject field OR by logging into www.freelists.org

- Unsubscribe at rollei_list-request@xxxxxxxxxxxxx with 'unsubscribe' in the subject field OR by logging into www.freelists.org

- Online, searchable archives are available at
http://www.freelists.org/archives/rollei_list

Other related posts: