Goerz Doppel-Anastigmat Series III No. 1 Question
Hey everyone, I've been looking online and after finding a few bits of information I'm still stumped.
I know it's a 150mm, for a 12x16cm plate - but this lens has a focusing helicoid. I cannot find anything about this. Worse yet - I can't get it to focus. I then took the lens apart, removed grease and re-lubricated, re-assembled properly and still no luck.
Why does it have a helicoid and how do I get this thing to work?!
It looks to me the lens doesn’t have the pair of the lens cells.
If so, the focal length doubles like 300mm, and that’s why the lens doesn’t behave like 150mm focal length lens.
Please confirm the lens has two cells.
I vaguely remember reading about another similarly machined/configured pre WWII lens. Idea was to separate the front and rear elements to achieve a soft-focus or diffusion effect, similar to a post WWII Wollensak Velostigmat Series II. Problem was that it allowed one to separate the front and rear elements way more than needed effectively making the optic unfocusable. Wollensack solved this over separation problem by machining the front element to just slightly unscrew forward to give it more distance from the other elements. So possibly the "focusing helicoid" on your lens was not for focusing but for providing diffusion.
It Does have both sets of cells.Originally Posted by mhayashi
It's definitely pre-war, I'd suspect it's possibly pre-WWI even. That's an interesting theory, but in it's current configuration it's locked and there are distance indicators of some kind on the barrel and a notch to indicate what that distance is.
Hmm. It is in what's called a deep mount, used with cameras that have focal plane shutters.
Which camera did you mount it on? How did you try to focus it?
I don't have the relevant tables for real Goerz Dagors but the nearly identical Boyer Beryl's back focus -- distance from the rear element's vertex to the film plane when the lens is focused at infinity -- is approximately one focal length. There's a hint.
I mounted it on a Canham DLC45 and focused with Bellows just fine. When I look the lens apart I noted that removing the two small screws on each side of the barrel (rear, past the flange), the lens would twist in in out of a helicoid, doing so allowed the distance markings on the inner barrel to correspond with the notch on the outer barrel. It would make sense that this came out of a focal plane shutter camera, I would assume a box or fixed bellows type camera - but the lens is such a hefty design for such a simple camera.
This lens in this focus mount was common on the Goerz Anschutz press cameras.
After Dan's comment I started looking and the lenses look similar - but I found nothing of the same design. I think you're on the money though.
Now, is this lens considered a Dagor? I read in the Lens Vade Mecum that the Dopel Anastigmat Series III were later renamed to Dagor, but I saw conflicting results on here saying that many times people just falsely claim that Goerz lenses are Dagors. This has two groups of cemented elements, but I cannot tell the layout of the individual elements.
I apologize for the questions, I'm just into researching and learning this odd ball stuff. I picked this lens up for like $50.
Look on the front page of this site. There's good article about Goerz lenses that may be of help.
IIRC C.P. Goerz changed the name from "Doppel-Anastigmat" to "Dagor" in the early 20th century. But there are historians and experts here who can probably be more accurate- perhaps they will speak up.
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