Rodenstock Anastignar 285mm

[CTwist]

Dear All,

I was wondering if your collective knowledge could shine some light on this lens: a Rodenstock Anastignar 285mm f/6. There seems to be very little information on the web. Not sure when it was made or what type of lens it is. I am guessing it's an improved Rapid Rectilinear rather than a bona fide post-1890 anastigmat. Does anybody know?

There's also a bit of a mystery on the focal length. It's marked as 285mm. When I calculate the FL using the simple lens rule, I get 320mm. To check my sanity, I used the same rule for an ApoSymmar 210mm (result 212mm) and a Busch Aplanat #3 (result 273mm). So is the lens bending the light in a strange way or is it mis-labelled? The field of view is definitely narrower than the Aplanat, but I don't know how to relate the angle of view to the FL.

Thank you for your help.
Best regards,
Charles

[CTwist]

I found a way of relating field of view to FL, and it's definitely around the 320mm mark. Is it common for the engraving on the lens to be out by 35mm? Rodenstock is hardly a brand known for low quality.
Thanks,
Charles

[Steven Tribe]

Doesn't ring a bell.
.......nar was popular with Rodenstock. Could this be an early name for what became the Eurynar various series?
Is this a dialyte (1+1--- 1+1)? A missing lens could account for the narrow angle and "wrong" focal length.

[CTwist]

Hello Steven,

The idea of a missing lens is intriguing because it might offer a way forward in the FL problem. Looking at the lens, it's basically a barrel with glass at both ends - there are no options for more glass within the barrel. The arrangement is very similar to a rapid rectilinear (Q5 in the vademecum). Is there any way of telling whether the glass at each end is a single lens element or a group of two or more lenses?

The actual glass comes out of its brass case. I can't see how anyone could have put an extra lens in there with an air space for a dialyte. However it is possible that the glass could have been replaced at some stage. Mitigating any tampering, the glass at both ends is identical, as far as I can tell.

Thanks for your help. Best regards,
Charles

[Ole Tjugen]

Funny - Thiele lists an Anastigmar, and no Anastignar. Yet Rodenstock have always been fond of the ...nar.

More funny, the Anastigmar is only known as a 215mm f/6 lens, most likely a 4 in 4 - or Dialyte.

An Anastgmat as originally defined consisted of an old achromat in teh front and a new achromat in the rear, and might well be 4 in 2, or 2+2 and hard to distinguish from an Aplanat.

[CTwist]

Thanks Ole.
Pictures are here.
The idea of a missing lens to explain the FL also fails on the fact that the lens gives quite a clear image - not soft or badly distorted.
Best regards,
Charles

[Sevo]

Funny - Thiele lists an Anastigmar, and no Anastignar. Yet Rodenstock have always been fond of the ...nar.

Well, it would not be surprising to see such an error in Thiele (where many data have been reported by collaborators and copied across several generations of hand written notes). And lens engravers have been wrong, too...

[Arne Croell]

Well, it would not be surprising to see such an error in Thiele (where many data have been reported by collaborators and copied across several generations of hand written notes). And lens engravers have been wrong, too...

I agree with Sevo; in addition to collaborators he mainly relies on the production lists from the companies, and the older ones are all handwritten and not always that legible (there are a few examples shown in his books). N and m and are not far apart both in the Latin alphabet and the old German "Sütterlin" letters, they are also next to each other on the keyboard, so given the huge number of entries in his lists, errors and typos will happen.

[CTwist]

If the lens is a dialyte, wouldn't it be strange that there is a single piece of glass that comes out of each of the front and rear cells? I can't imagine that the two pieces of glass would be stuck to each other around the rim. Or am I deluded?
Thank you. Best regards,
Charles

[Ole Tjugen]

Rodenstock made some strange lenses, I have a Hemi-Anastigmat f:7.2 which has 3 elements in 2 groups - doublet front, single rear. Meybe the Anastignar is something like that?