Identify This Goerz Lens

[neil poulsen]

I'd like to get some input on this lens. From the label, it was made by the C.P. Goerz American Optical Co. It has a serial number of R796634. The lens is about 42mm tall, and the thread size is about 40mm.

It was kind of a door prize at a recent photographers' meeting/gathering. A member had brought in a box of give-aways, and the leader of the organization held each one up and offered it to the first person who expressed interest. Since there was no focal length info for this lens, no one wanted it until I finally spoke.

I speculate that this is an 8 1/4" Dagor. Focusing on a distant object, it's about that distance from the plane of focus to the longitudinal center of the lens. The maximum aperture is f6.8, which "seems like" almost a dead give-away. It's minimum aperture is f45. In the third photo, I directed a point-source light of small diameter at the lens from above the camera. Taking a look at the two pairs of brightest (out-of-focus) dots, each pair are about equidistant apart. Looking at them by sight, both dots of one pair is decidedly lower than both dots of the other pair. I make these four dots to be reflections from four air-to-glass surfaces. So, it would appear to me that this lens has two symmetric (since pairs of dots are equidistant?) groups with four air-to-glass surfaces. This is also consistent with the conjecture that this lens is a Dagor.

It's also of interest that this is a late Goerz lens. It's factory coated. From the LF page, I'd say this lens was made in about 1960, plus or minus a couple of years. In 1963, the C.P. Goerz American Optical Co. changed their name. (See: http://www.largeformatphotography.info/classic-experts.html )

What do you think? Is my analysis correct? One question is that, being a barrel lens made when shutters were plentiful, was this lens optimized for infinity, or is it more of a process lens? But then, it seems likely that, as a process lens, it would have been an Artar, which isn't a symmetrical lens. Since it wasn't mounted in a shutter, for what use or camera was this lens intended? Also, what does the "R" mean in the serial number. I saw an EBay listing of a Goerz barrel lens, and its serial number began with a "K".

I've included three, not so good, photos. The lens is actually MUCH cleaner than that suggested in the photos. (Fortunately!) These point and shoots really emphasize contrast.

[E. von Hoegh]

Some say the "R" is for "Robertson" a maker of process and copy cameras - seems plausible. "K" was "Kenro". The fact that it's f6.8 means little, there was an f6.8 Syntor (Dialyte type) Goerz lens. But this is a Dagor type; I don't know what it's optimised for.
Nice find! Make a negative and see what it does.

BTW, the Artar is a Dialyte symmetrical type and has a narrow angle of view, perhaps someone needed a wider angle but not apochromatically corrected lens.

[neil poulsen]

Some say the "R" is for "Robertson" a maker of process and copy cameras - seems plausible. "K" was "Kenro". The fact that it's f6.8 means little, there was an f6.8 Syntor (Dialyte type) Goerz lens. But this is a Dagor type; I don't know what it's optimised for.
Nice find! Make a negative and see what it does.

BTW, the Artar is a Dialyte symmetrical type and has a narrow angle of view, perhaps someone needed a wider angle but not apochromatically corrected lens.

Thanks for the information and for your input on the f6.8.

I checked with S.K. Grimes, and when they mount a lens, they reproduce the exact barrel dimensions. They don't space the groups so as to optimize for infinity, or something nearer.

[CC Tarca]

Artars ARE symmetrical and air-spaced: ()-)(-)(-() This could well be one.

[Peter Yeti]

A Dialyte like the Artar would give a different pattern of reflections in the flashlight test. Most likely, you would find four pairs of reflections of which two are closely spaced and two are wider spaced. The third photo above shows the typical Dagor pattern plus some additional reflections spoiling the test.

[neil poulsen]

Since they're not the same brightness, I was wondering if the additional dots might be from glass to glass surfaces, that make up each group. This was a very bright, tiny light on my phone that doubles as a flash. I have an app that turns this flash into a flashlight.

[Peter Yeti]

You are right, there are weaker secondary reflections, which are also characteristic. I quickly made a photo of one of my Dagors for you, showing the typical pattern. There are two strong and one weak reflection for each anastigmat element. The two groups of three reflections are related by an inversion at the centre of the lens. Hope it helps to identify your lens.

97415

[E. von Hoegh]

Artars ARE symmetrical and air-spaced: ()-)(-)(-() This could well be one.

No it couldn't. a) The reflections are wrong. b) Artars are f:9, f:9.5, and f:11 in the longest focal lengths. According to Goerz catalogs there has never been an Artar faster than f:9.

[Fotoguy20d]

The easiest way to count the reflections is to take a cell out of the barrel. It's definitely not an Artar (unless someone put the cells in a Dagor barrel). I have a 12" Artar with an R serial number and Robertson's name on it. That barrel uses a waterhouse slot. I also have an 8 1/2" Dagor in Kenro marking and a K serial number. Both are coated. The barrel spacings are different but the threads are the same, as it happens,so they could be swapped. Dagors should show 2 bright and 2 dim reflections (3 cemented pieces of glass) per cell. Artar should show 4 bright (2 uncemented glasses per pair) per cell, but so would a Syntor or any other Dialyt type.

Dan

[Dan Fromm]

There are two strong and one weak reflection for each anastigmat element.


No, two strong and two weak. Two air-glass interfaces, one at each end of the group and two glass-cement-glass interfaces, between the first and second and second and third elements.

[Peter Yeti]

Dan,

you are right in theory but in practice I cannot find a fourth reflection for each group, at least not in the photo. Just look at the photo and count. I think the fourth reflection is so weak that it's hardly visible. It's exactly the same with my other Dagor.

[Fotoguy20d]

It's easy to find if you know where to look. Stand directly under a light source and tilt the lens away from you around 5-10 degrees. It'll appear from the lower bright spot. Harder to spot on a 5-6" lens than an 8-10" but its there.

Dan

[E. von Hoegh]

It's easy to find if you know where to look. Stand directly under a light source and tilt the lens away from you around 5-10 degrees. It'll appear from the lower bright spot. Harder to spot on a 5-6" lens than an 8-10" but its there.

Dan

Yes it is, at least on the six I have. The reflections from the cemented surfaces stand out better on the coated versions.

I notice Peter's lens is marked in mm. I have two Berlin Dagors, 240mm # 260383 and 30cm #657010. I wonder when they switched from mm to cm?

[Fotoguy20d]

I have 27cm of the same vintage as your 30 and 150mm in 365737. My others are either American (9 3/4, 8 1/2, and 5 in) or pre-1900 vintage (150mm and 210mm both in 70000 range).

Dan

[Dan Fromm]

Dan,

you are right in theory but in practice I cannot find a fourth reflection for each group, at least not in the photo. Just look at the photo and count. I think the fourth reflection is so weak that it's hardly visible. It's exactly the same with my other Dagor.

Peter, nowhere is it written that reflections from glass-cement-glass interfaces must be easy to see. You were mistaken and are defending an indefensible position, viz., "what I can't see isn't there."

I too have had difficulty seeing weak reflections. For example, I once mistook a Lomo RF-5 for a dialyte because I couldn't see a weak reflection from its inner groups; the lens is in fact a 6/4 double Gauss type. After Arne Croell told me that I was mistaken and that the weak reflections were there, I found them. One has to look hard.

The best, perhaps the only good, way to count reflections from a lens' cells is to look at the cells one at a time. Extract them from barrel or shutter, dismantle them as far as possible. You can't tell shit from a picture of a lens.

[E. von Hoegh]

I have 27cm of the same vintage as your 30 and 150mm in 365737. My others are either American (9 3/4, 8 1/2, and 5 in) or pre-1900 vintage (150mm and 210mm both in 70000 range).

Dan

Thanks Dan. I think I'll start keeping track. The two in the 70,000 range, are they f;7.7 versions?

[Fotoguy20d]

I'm not sure - I'll have to check. One came in a B&L Iris Shutter with a F&S NYC Cycle Graphic. The other (150mm) came in a battered, ancient, sector shutter (missing the diaphram dial among other issues) - but, I made a mistake on that one - it's in the low 38 thousands, not 70s. I also have a 210 in brass barrel at 88000. Didnt realize I had so many of them.

Dan

[neil poulsen]

From the discussion, it sounds like I definitely have a Dagor. But the spacing is unclear, whether it's optimized for infinity or otherwise.

Either way, I may have this lens mounted in a shutter. It's $325 at S.K. Grimes, assuming that I have a spare shutter that would work. I have a Polaroid shutter intended for Tominons that might work. I'll check.

Thanks very much for the discussion and information.

[Roger Hesketh]

Neil I have one too. Serial number R 827975. I recall asking Andrew Glover his opinion about the lens. I speculated that it was a Dagor. I seem to remember him saying that he thought it was too. However it was at least ten years ago and I struggle to remember what I was doing last week these days. He did however list another very similar lens as a Process Dagor not that long afterwards .

I do remember how I came by it though. I bought it in a lot with a Wray 12" Lustrar in an auction which finished on Christmas day about 2.30pm in the afternoon. It was a ten day auction and I felt sure someone would spot it. They did not and I won the auction for $22. My Christmas pressie to myself!

Mine will cover 8x10 when stopped down so it is definitely not a dialyte type lens. I also seem to recall discussions at the time suggesting it might fit straight into something but I do not recall what. I have a Graflex 8x10 accessory focal plane shutter so have had no need to shutter it. I have only used it a few times and those pictures were poor not the fault of the lens but due to operator error by the clot under the dark cloth.

It is not a focal length I tend to use much on 8x10. Maybe that will change. Maybe I should shutter it as one of the main reasons I do not use it is I can barely achieve infinity focus with the lens when used on my B&J camera with the accessory shutter fitted. I keep it because If I was to sell it their is no way I could afford to buy a lens of comparable quality for the price I would get for it should I later decide to use that focal length for 8x10 work. I would use it on 5x7 but I have a shuttered 8 1/2 " Commercial Ektar which is mainly pressed into service on that format. Thinking about it now it could possibly see some use as a semi wide on my latest project, 5x12.

My lens has a lovely blue coating. Sorry Neil but due to the problems already mentioned I have never used it focused at infinity but I suspect it will be fine. A Dagor is a symmetrical lens anyway and is at it's optimum at 1:1 so I cannot see their is any need for a Process Dagor to be any different from any other Dagor.

[E. von Hoegh]

Neil I have one too. Serial number R 827975. I recall asking Andrew Glover his opinion about the lens. I speculated that it was a Dagor. I seem to remember him saying that he thought it was too. However it was at least ten years ago and I struggle to remember what I was doing last week these days. He did however list another very similar lens as a Process Dagor not that long afterwards .

I do remember how I came by it though. I bought it in a lot with a Wray 12" Lustrar in an auction which finished on Christmas day about 2.30pm in the afternoon. It was a ten day auction and I felt sure someone would spot it. They did not and I won the auction for $22. My Christmas pressie to myself!

Mine will cover 8x10 when stopped down so it is definitely not a dialyte type lens. I also seem to recall discussions at the time suggesting it might fit straight into something but I do not recall what. I have a Graflex 8x10 accessory focal plane shutter so have had no need to shutter it. I have only used it a few times and those pictures were poor not the fault of the lens but due to operator error by the clot under the dark cloth.

It is not a focal length I tend to use much on 8x10. Maybe that will change. Maybe I should shutter it as one of the main reasons I do not use it is I can barely achieve infinity focus with the lens when used on my B&J camera with the accessory shutter fitted. I keep it because If I was to sell it their is no way I could afford to buy a lens of comparable quality for the price I would get for it should I later decide to use that focal length for 8x10 work. I would use it on 5x7 but I have a shuttered 8 1/2 " Commercial Ektar which is mainly pressed into service on that format. Thinking about it now it could possibly see some use as a semi wide on my latest project, 5x12.

My lens has a lovely blue coating. Sorry Neil but due to the problems already mentioned I have never used it focused at infinity but I suspect it will be fine. A Dagor is a symmetrical lens anyway and is at it's optimum at 1:1 so I cannot see their is any need for a Process Dagor to be any different from any other Dagor.

Just because a lens is symmetrical does not mean that it is "at it's best" at 1:1. It's at it's best at whatever ratio it was optimised for. There might be slight changes in the radii of curvature of the glasses in one cell, changes in the spacing relative to the aperture on one side, etc. etc.

Dagors are pretty critical regarding spacing - much more so than it's descendant the Plasmat.

[Roger Hesketh]

Just because a lens is symmetrical does not mean that it is "at it's best" at 1:1. It's at it's best at whatever ratio it was optimised for. There might be slight changes in the radii of curvature of the glasses in one cell, changes in the spacing relative to the aperture on one side, etc. etc.

Dagors are pretty critical regarding spacing - much more so than it's descendant the Plasmat.

I always find it helpful if someone who takes issue with something I have said then goes on to make my point for me. Thank you.

You are quite right just because a lens is called or considered to be a to be symmetrical lens it does not necessarily mean that the lens is truly symmetrical in it's construction.

You were also right to correct my sloppiness of expression regarding a Dagor's optimal performance being at 1:1.

I naturally assumed that a lens which relies so heavily upon correct spacing to maintain it's performance and upon it's symmetry to correct aberrations would have to be truly symmetrical in it's construction.

Clearly you consider my assumption to be incorrect and that you know different. I and I am sure many of us would be grateful if you could share your insight with us. The point I was trying to make for the benefit of the OP is that due to the nature of its construction a Process Dagor is unlikely to differ significantly in it's performance from that of a Series III or other standard Dagor lens.

One of the things I most enjoy about this forum is the willingness of many of it's members to share their experience and knowledge.

[E. von Hoegh]

I always find it helpful if someone who takes issue with something I have said then goes on to make my point for me. Thank you.

You are quite right just because a lens is called or considered to be a to be symmetrical lens it does not necessarily mean that the lens is truly symmetrical in it's construction.

You were also right to correct my sloppiness of expression regarding a Dagor's optimal performance being at 1:1.

I naturally assumed that a lens which relies so heavily upon correct spacing to maintain it's performance and upon it's symmetry to correct aberrations would have to be truly symmetrical in it's construction.

Clearly you consider my assumption to be incorrect and that you know different. I and I am sure many of us would be grateful if you could share your insight with us. The point I was trying to make for the benefit of the OP is that due to the nature of its construction a Process Dagor is unlikely to differ significantly in it's performance from that of a Series III or other standard Dagor lens.

One of the things I most enjoy about this forum is the willingness of many of it's members to share their experience and knowledge.

Then why did Goerz make the Process Dagors (series iv?) and later the Trigors, if there's no significant difference?

I'm not at all clear what you are asking here. I get the feeling you're just venting a bit of sarcastic spleen because I corrected you. If so, it's not a good way to get me or (anyone else) to respond in a positive manner.

[Dan Fromm]

Folks, if Eric got his patent information correctly and Goerz actually constructed lenses that conform to their patents the Dagor is well and truly symmetrical. See http://www.dioptrique.info/base/n/n_dagor.HTM and http://www.dioptrique.info/OBJECTIFS7/00317/00317.HTM

So is the Boyer Beryl, a Dagor clone. See http://www.dioptrique.info/OBJECTIFS4/00198/00198.HTM

[Roger Hesketh]

The great virtue of a symmetrical lens construction is the almost automatic correction for coma,distortion and lateral chromatic aberration. One set of glasses really furnishes a lens with a stop behind it, the other a lens with a stop in front of it. Each of these contributes coma, distortion and lateral chromatic aberration of the same amount but of opposite signs or directions,provided and it is an important proviso-that the object and the image are at the same distance from the lens,as happens in full size copying work. When the lens is used with the object at a considerable distance from the lens as is normal in photographic work this automatic balancing of aberrations is no longer obtained. But the lack of balancing that is now introduced is not responsible for more than a trace of any of these aberrations appearing in the lens.What coma distortion and lateral colour are introduced by the change from copying to normal conditions can be removed by making slight changes to the curves of one glass while retaining the other set unchanged. In the majority of lenses below it will be taken for granted that such changes have been made even if it is not specifically referred to and since it does not upset the symmetry of the construction they will still be referred to as symmetrical lenses even though they depart slightly from this precise balancing.

Not my words Arthur Cox's in Optics The technique of definition Focal Press 1945.

I have always understood the Dagor to be a truly symmetrical lens. Same both sides of the stop. Therefore it gives its optimal performance at 1:1. So I fail to see any reason why a Process Dagor should be designed any differently. Could achieving more sales have something to do with the different names. Lenses very similar to Neil's and mine have also I believe have had gold paint applied to them as an indication of quality.