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Pfeiffer Duckett
5-Jun-2008, 11:38
I have a 130mm Goerz Dagor- I recently read that you can remove either the front or rear element from these to effectively double the focal length- I'm moving up to 8x10 and don't have a lens for my new camera yet.

I know my Dagor won't cover as it is, but will I be OK if I remove one of the cells?

Bill_1856
5-Jun-2008, 11:53
I don't think so (but you never know 'til you try it). Even stopped down, the lens suffers significant loss of sharpness and focus shift. Incidentally, the actual focal length increase is 1.75X, and it's best to use the REAR element and a medium yellow filter.

John Schneider
5-Jun-2008, 12:07
You're probably thinking of a convertible Protar VII, which was better corrected, and could be used with the rear cell alone.

Ole Tjugen
5-Jun-2008, 12:50
Dagors and all other "doppel-anastigmats" were designed to be convertible. However the resolution suffers quite a bit, and the angle of coverage drops drastically - so much so that the image circle of a single cell is smaller than that of the complete lens.

The only lenses which give decent results at wide-ish apertures when converted are those with four or more elements per cell, even if one or more of those elements are air. Examples are the Protar VII, the Plasmat, the Octanar, and a few more even rarer ones.

seawolf66
5-Jun-2008, 15:03
try this place and read what lenses do what in the Dagor 6.8 line:
http://www.cameraeccentric.com/html/info/goerzcat/dagoranasb.html
good luck and have fun

E. von Hoegh
8-Jun-2008, 15:52
Dagors and all other "doppel-anastigmats" were designed to be convertible. However the resolution suffers quite a bit, and the angle of coverage drops drastically - so much so that the image circle of a single cell is smaller than that of the complete lens.

The only lenses which give decent results at wide-ish apertures when converted are those with four or more elements per cell, even if one or more of those elements are air. Examples are the Protar VII, the Plasmat, the Octanar, and a few more even rarer ones.

The focal length of a single cell of a Dagor is very nearly twice the focal length of the combination. The image circle of the single cell is much larger than the combination; although the angle of coverage may be smaller.

The qualty is subjective; I've used a 210 and a 300 rear cell on 8x10, and it's good enough for a contact print.


Mr. Tjugen; I apologise for contradicting you.
However, these are the results I have on the negatives.

Ole Tjugen
8-Jun-2008, 16:16
No apologies needed - "coverage" has always been subjective.

With an appropriate scene I won't hesitate to use half a Dagor - or even half an Angulon, or use a (whole) 90mm Angulon on 5x7" film. It all depends on what is in the corners, and how important corner sharpness is.

E. von Hoegh
8-Jun-2008, 16:38
No apologies needed - "coverage" has always been subjective.

With an appropriate scene I won't hesitate to use half a Dagor - or even half an Angulon, or use a (whole) 90mm Angulon on 5x7" film. It all depends on what is in the corners, and how important corner sharpness is.

I have a "Linhof select" 90mm Angulon that does just fine with 5x7 right out to the corners.

I have another that barely covers 4x5 sharply. It was made about 6 years before the Linhof version.

Have you ever looked at the original Dagor patent?

It covered the "Angulon" (reverse Dagor) design as well.

Ole Tjugen
8-Jun-2008, 17:28
I have; and I've used Dagor, Angulon (different vintages with different characteristics), Doppel-Amatar, Collinear, Protar VIa, and Hexanar. All of them are 3+3 "Dagor", "reverse Dagor" or some other version of that. And strangely enough they are all different - in some cases very different. :)

E. von Hoegh
9-Jun-2008, 04:46
I have; and I've used Dagor, Angulon (different vintages with different characteristics), Doppel-Amatar, Collinear, Protar VIa, and Hexanar. All of them are 3+3 "Dagor", "reverse Dagor" or some other version of that. And strangely enough they are all different - in some cases very different. :)

They certainly are "very different!"

I've read that the Kern MC Dagors are soft. Well, mine certainly isn't! I also have a 210 Dagor type that is one of the sharpest lenses I've ever seen - it's eerie. I'd love to know who made it.

My Linhof Angulon is ca. 1960; the sample to sample variation with these is well known.

seawolf66
9-Jun-2008, 14:13
The performation of a lens can only be decided by its use, in the camera of your choice! a lot of folks Expect a lens to do something more than it can, But the fun
is in use-ing the lens and being surprised at the results in the end, So I am told but I used my old [new] Goerz Double Anastigmatic lens SerieIII no 1 F/6.8 6-1/2 focus with my very old R.O.C. Pony Premo # 6

So I say this," use it" and then if it does not preform "Lose it":

Dan Fromm
9-Jun-2008, 14:30
Lauren, you have the right of it. When in doubt, ask the lens.

But we have, collectively, short memories or forget deliberately. There's been considerable disagreement on this forum about exactly how wonderful Dagors are. See, for example, this long thread: http://www.largeformatphotography.info/forum/showthread.php?t=13109 And read all of it, towards the end it gets quite, um, surreal.

Cheers,

Dan

E. von Hoegh
9-Jun-2008, 14:57
Lauren, you have the right of it. When in doubt, ask the lens.

But we have, collectively, short memories or forget deliberately. There's been considerable disagreement on this forum about exactly how wonderful Dagors are. See, for example, this long thread: http://www.largeformatphotography.info/forum/showthread.php?t=13109 And read all of it, towards the end it gets quite, um, surreal.

Cheers,

Dan

Ahh yes, good ol' landarc. I remember it unfondly.

That thread is info re:landarc, not info re:Dagors.

I mean, FFS.

John Schneider
9-Jun-2008, 15:15
The details of the circumstances surrounding that thread are a bit foggy in my memory, but basically landarc disingenuously started that thread in an to attempt to skew an eBay auction he was involved in. I would disregard the entire thread if you're trying to gather information on the performance of Dagors.

E. von Hoegh
9-Jun-2008, 15:21
The details of the circumstances surrounding that thread are a bit foggy in my memory, but basically landarc disingenuously started that thread in an to attempt to skew an eBay auction he was involved in. I would disregard the entire thread if you're trying to gather information on the performance of Dagors.

You are 100% correct, Mr Schneider.

Dan Fromm
9-Jun-2008, 16:12
Come on, guys. In that thread, people stood up to bear witness that their 7" Dagors were and weren't sharp, did and didn't cover 8x10, and that it is/isn't reasonable to expect flat out lies from people who offer lenses for sale on eBay. The discussion has a strong, um, revival meeting aspect.

John, please do refresh your memory be reading. You too, Billy.

seawolf66
10-Jun-2008, 05:00
Dan: thanks to you , I finally found out what I am missing in Life, Heavens A Refresh Button , would that have not, saved me a lot of problems:

Sorry Dan could not let this one go by :

Ernest Purdum
10-Jun-2008, 10:12
In general, most (I can't think of an exception) symmetrical lenses, starting with the Rapid Rectilinear, will produce an image with the front cell removed, but how satisfactory will differ from one user to another.

My thought is if you've got it, try it. If you don't have it, don't spend much unless it is one of those specifically designated as convertible, the Protar Seies VIIa being the most prominent example.

While on this subject, there is a trap on the VII lens markings. It is common for Series VIIa lenses to be adverised as maybe 13 3/4", when the actual focal length is perhaps 7". The seller isn't trying to cheat you, he is going by the markings he sees, which is that of the front cell alone.

Pfeiffer Duckett
10-Jun-2008, 13:39
Well-

Here's a stumper:

I was taking a look at my lens- its been set in a copol 0 since I got it, and it has two aperture scales engraved on the front- one in green that runs from 6.8 to 32, and another that runs from 8-32. Both are in different places- that is to say, f/11 and f/11 are in two different spots. I've always assumed that the first is for both cells, and the other for single. But taking a good look at the shutter, I've noticed a third aperture scale engraved underneath the speed scale that runs 6.3 to 36.

Ahhhh, I think I just figured it out. I bet the person who had this lens before me was just carrying around cells and swapping them into the same shutter to save space or monies.

Well, since I don't really have a question anymore- anybody else routinely figure out what they're trying to ask halfway through a post?