This is a general purpose large format lens launched in 1968. Later, it appeared also Sironars N and S, redesigns around the same concept using different glasses. This 240 mm f5.6 is very impressive in a Compur 3 almost falling off the Technika 4x5 lens board. Coating reflects white light in nice purple hue and renders the glass beautifully transparent. Proof that it does its job.



The construction idea, based in an air spaced Dagor , is know since 1911 in a lens called Euryplan. Lens of this kind are known as Plasmats due to a famous series designed by Paul Rudolph, the legendary lens designer originally from la maison Carl Zeiss in Jena. But the Plasmats, he did for Hugo Meyer in Gorlitz. He was already retired but due to hardship after the WW I, at the age of 61, he resume working in that smaller company.



There are different opinions in forums on the web about this lens being or not symmetric. There are indications that the early ones were not and could be used as triple convertibles. (foci A, B and A+B are different). This sample I have seems to be symmetric. The front element is not unscrewing easily and I don't want to force. These lenses are said to be prone to separation. I am afraid some tensions while forcing it to turn would result cement flaws. According to its serial number, it is from 1973



An indication that this one is symmetric is that the shutter seems to be original and indicates only two foci: 240 and 700 mm, with different aperture scales. Rodenstock indicates that the front element can be used alone for portraiture. I would love to but imagine the bellows extension for a portrait using a 700 mm





This lens, 240 mm, covers 18x24 cm, but I have been using it mostly in 9x12 cm because it is mounted in a Technika 4x5 board.

Most of the above information I researched on "A history of the photographic lens" by Rudolf Kingslake, Academic Press Inc. ISBN 0-12-408640-3. It is an excellent source for understanding the genealogy of most of the lenses ever produced and the problems associated to lens construction.
If you want something online: download the "A Lens Collector Vade Mecum" it is only 15,99 USD and an invaluable source of information. Go to: Lens Vade Mecum It has more than 700 pages with thousands of lenses description, pictures and diagrams.