PDA

View Full Version : Goerz Dogmar 180mm f4.5 image circle?



koh303
19-Jan-2015, 09:23
I am trying to find info about this Goerz lens.
Not much around except a google search which brought up that NYC Goerz Dogmars covered 50 degrees.

Can anyone shed any light on this lens?

It covers 4X5 for sure, but wondering if it is good for anything else...?

djdister
19-Jan-2015, 10:06
I am trying to find info about this Goerz lens.
Not much around except a google search which brought up that NYC Goerz Dogmars covered 50 degrees.

Can anyone shed any light on this lens?

It covers 4X5 for sure, but wondering if it is good for anything else...?

There are 4 Goerz catalogs (1913, 1915, 1940, 1951) on the cameraeccentric.com website, but unfortunately none of them list a 180mm Dogmar lens.

koh303
19-Jan-2015, 10:08
This one indeed reads 18cm F4.5....

koh303
19-Jan-2015, 10:11
In the 1915 catalog there is a dogmar 7" listed, but the price only. I am re reading that to see of any info on coverage.
The much later catalog lists 48 degrees at f4.5, so i guess it is 4X5 and no more...
Still a cool little lens.

djdister
19-Jan-2015, 10:14
This one indeed reads 18cm F4.5....

Right. The catalogs on the cameraeccentric website are all "Goerz American Optical" whereas the 18cm lens shown in a closed ebay listing shows it on a German camera with the Deutsches Reichspatent (D.R.P.) marking. Guess you need the German catalog.

koh303
19-Jan-2015, 10:17
This lens is a berlin goerz (as noted in the first posting). I know there is a difference in Dagors, and so safe to ass ume that these are also different?

Louis Pacilla
19-Jan-2015, 10:42
In the 1915 catalog there is a dogmar 7" listed, but the price only. I am re reading that to see of any info on coverage.


Click on this & it will take you to a few post discussing the Dogmar.http://www.largeformatphotography.info/forum/search.php?searchid=4036100

You are not going to find anything beyond the fact that the Dogmar is a Gaussian type w/ eight to air surfaces so will be low in contrast unless coated as you stated the design has a max 50 degree coverage and nothing beyond that. The lens may be used up to 5x7 but w/ little left for movements but a nice lens for 4x5.

It is often found in sunken mount in shorter FL as the where meant to be Goerzs "speed lens" & used on FP reflex cameras.

mdm
19-Jan-2015, 11:14
I have used a 165 dogmar on 5x7. I have an example somewhere on 5x7 film but can't find it, not shure bout infinity though. They may cover more than suggested. These are on fp100C. They have the most amazing colour rendition and I compared with a sironar s which was cooler and more muted. They are convertible and either the front or back elements an be used for 2 different longer focal lengths, but are very soft that way. Recently I put mine in the goer pile because I have sold some stuff but it seems to be happy here.
http://4.bp.blogspot.com/-KHzQgdiGSq0/TYJmOqxJNEI/AAAAAAAAApo/Ai5L5mlz6xs/s1600/yellow.jpg http://3.bp.blogspot.com/-kPcdiKp0y9s/TYBvhJ6k9_I/AAAAAAAAApI/g3pVYC7eH0w/s320/red.jpg

mdm
19-Jan-2015, 11:37
first is on 5x7, second is single element on 5x7
http://www.largeformatphotography.info/forum/attachment.php?attachmentid=52203&d=1288942654 http://www.largeformatphotography.info/forum/attachment.php?attachmentid=52204&d=1288942686

koh303
19-Jan-2015, 14:23
first is on 5x7, second is single element on 5x7
http://www.largeformatphotography.info/forum/attachment.php?attachmentid=52203&d=1288942654 http://www.largeformatphotography.info/forum/attachment.php?attachmentid=52204&d=1288942686

very cool. thanks for the info!

Peter Yeti
19-Jan-2015, 17:11
There is quite a bit of info for this lens but unfortunately it's very scattered. This was a tremendously successful and widespread amateur lens on the German market in the time roughly between 1910-1926 and was a standard on the popular and high quality Tenax folding camera by Goerz (4.5/135mm for 9x12cm). Thus, 4.5/18cm points to a design for 13x18cm, though probably with little room for movements.

It's a symmetrical 4 elements in 4 groups dialyte design (+--+) like many others and capable of very sharp and high-res images but prone to flare. It is similar to Steinheil's Unofocal but has lenses with more pronounced curvature, iirc. This was the trick to achieve good contrast because it helped to lead stray light to the walls of the barrel rather than onto the film. This way you end up with only a small loss in effective speed but not in contrast. I have a very similar lens, a Hugo Meyer Helioplan of the same period, which uses the same principle and is an excellent lens, particularly for close-up work. I think those lenses were so popular because of a slightly lower price compared to a Tessar yet providing very good image quality.

Peter

koh303
19-Jan-2015, 17:39
There is quite a bit of info for this lens but unfortunately it's very scattered. This was a tremendously successful and widespread amateur lens on the German market in the time roughly between 1910-1926 and was a standard on the popular and high quality Tenax folding camera by Goerz (4.5/135mm for 9x12cm). Thus, 4.5/18cm points to a design for 13x18cm, though probably with little room for movements.

It's a symmetrical 4 elements in 4 groups dialyte design (+--+) like many others and capable of very sharp and high-res images but prone to flare. It is similar to Steinheil's Unofocal but has lenses with more pronounced curvature, iirc. This was the trick to achieve good contrast because it helped to lead stray light to the walls of the barrel rather than onto the film. This way you end up with only a small loss in effective speed but not in contrast. I have a very similar lens, a Hugo Meyer Helioplan of the same period, which uses the same principle and is an excellent lens, particularly for close-up work. I think those lenses were so popular because of a slightly lower price compared to a Tessar yet providing very good image quality.

Peter

that's very helpful, thanks.

I am thinking about making this a portrait lens on a graflex or other walkaround camera...

The problem is that when the aperture is open all the way to 4.5 the shutter will not fire. I suspect some corrosion on the blades makes them to thick when they are compressed when open all the way pressing on the shutter blades... so you can shoot at anything but 4.5 ... :(

Jim Galli
20-Jan-2015, 10:37
very cool. thanks for the info!

When you're inches away from a subject instead of many feet, the image circle gets bigger.

You can come up with a real number by picking a point on a piece of graph paper (node, sort of) and then moving back to your 180mm or simile. Then get a protactor and do 25 degree angles from the node to the 18cm plane. Measure the resulting distance on the image plane, and that's your circle that your covered diagonal has to fit in.

People with smart phones probably have apps to do this but I'm old school and still sketch things on paper.

Peter Yeti
20-Jan-2015, 14:18
You can also measure the angel at which complete vignetting sets in, which is easy with a view camera. I did this for my Unofocal and Helioplan and came up with 75 and 80 compared to 90 for a Dagor. However, this might not be the usable image angle because of abberations. A Dagor is so well corrected that one practically can use the full 90 when stopped down a little. That's not true for the other constructions. The Celor/Syntor was improved, resulting in the Dogmar, by making it slightly asymmetric to correct for certain abberations but koma was not removed completely. This should reduce the useful image angle, depending how picky you are about image quality.

If your primary use is for portrait, you probably won't need much movements. In this case it should be fine for 5x7. But be aware that it's a very sharp lens, not soft focus at all. What shutter is it in? A CLA might come close to the value of the lens.

Peter

koh303
20-Jan-2015, 14:49
Its in a classic compur shutter.

The shutter has a problem where one of the aperture blades is out of alignment and causes the diaphragm to seize when it is wide open...

Its most definitely not worth a CLA, with some careful use it works just fine.

Dan Fromm
20-Jan-2015, 14:51
A Dagor is so well corrected that one practically can use the full 90 when stopped down a little.

Peter, Dagors' coverage is one of those topics about which people disagree, at times almost to the death. Here http://www.largeformatphotography.info/forum/showthread.php?13109-Lousy-Dagor is an interesting discussion whether Dagors have much coverage -- your position -- or not all that much -- some, not all, others' take.

Peter Yeti
20-Jan-2015, 15:44
Its in a classic compur shutter.

The shutter has a problem where one of the aperture blades is out of alignment and causes the diaphragm to seize when it is wide open...

Its most definitely not worth a CLA, with some careful use it works just fine.

If you have a steady hand and are brave enough, you might be able to fix it yourself. Iirc, the aperture blades are accessible from the rear side without disassembling the escapement and setting mechanism, which is in the front. The blade might be corroded or bent, not a big deal to correct with a bit of experience. But please take my words with caution, I'm restoring vintage swiss watches for fun and relaxation.

Peter

Peter Yeti
20-Jan-2015, 16:39
Peter, Dagors' coverage is one of those topics about which people disagree, at times almost to the death. Here http://www.largeformatphotography.info/forum/showthread.php?13109-Lousy-Dagor is an interesting discussion whether Dagors have much coverage -- your position -- or not all that much -- some, not all, others' take.

Dan, thanks for the link and the worthwhile comment. I read the first few posts of the thread and then stopped because I don't like religious wars, especially not about old lenses. You are an expert on lenses and I think you might agree that usable image angle depends a lot on what are the expectations. The answer will be different between the final image being an 8x10" contact print or an 8x10' enlargement with viewers almost sticking their nose on.

Lets put it this way to avoid confusion. If I use a 100+ year old lens, I certainly don't expect or even want to get resolution and contrast like from the latest quality Plasmat. Otherwise I would simply use that Plasmat of my favourite maker. I, personally, love the characteristics (other word for optical abberations;)) of my Dagors and some of it vanishes very quickly when stopping down. That's at least my experience. Recently, I made two test shots with a 7.7/180 Dagor (Series III) from 1904 and a 5.6/180 Symmar-S from 1974 (OK, not that recent) both at f/16. Unfortunately, I forgot to mark the negatives and guess what, I wasn't able to tell them apart afterwards.

By the way, I'd agree that according to modern standards the usable image angle of a Dagor would be around or less than 70. Anything else would be very surprising. The Plasmat is an improved Dagor in which the inner lens is separated from each triplet, giving additional degrees of freedom for optimization. It gives excellent results up to 72-75 and it's certainly "better" than a Dagor, especially when used wide open. But if you like the special "character" of a Dagor, you might not object to what it does beyond 70, particularly when stopped down.

But back to the Dogmar. You can't expect more from a Dogmar than you get from a Dagor. Maybe that's the reason why rumor has it that it's usuable image angle is around 50-60. In the end there is no way around (valid for any old lens) trying it out and see if one likes what it does.

Peter

koh303
20-Jan-2015, 17:41
If you have a steady hand and are brave enough, you might be able to fix it yourself. Iirc, the aperture blades are accessible from the rear side without disassembling the escapement and setting mechanism, which is in the front. The blade might be corroded or bent, not a big deal to correct with a bit of experience. But please take my words with caution, I'm restoring vintage swiss watches for fun and relaxation.

Peter

Ive previously had this generation compurs open and as far as i saw the aperture is below everything else, and the case of the shutter is closed from the back. I will have to take another look tomorrow, but i am pretty sure thats the way it is. Some newer copals and compurs have secondary casing inside that allows access to the aperture without taking anything off other then the face plate...

Dan Fromm
20-Jan-2015, 18:16
Peter, thanks for the kind words. I'm glad you saw that I didn't want to start a fight. You're right, no two of us have the same goals, consequently we see what our objectives do differently.

I hope you read far enough down the thread to find that the person who started the brawl ("my lousy 180 Dagor won't cover 8x10") sold 180 Dagors on eBay with claims that they covered 8x10. I found that hilarious. The biter bit, or, lies come home.

I've never really understood what Goerz' naming system for dialyte taking lenses for folding cameras tells us about the lenses. As I understand it Dogmars are better than Celors (which came first), which are better than Tenastimats and all the other ones whose names start with Ten-, which are better than the ones with no name but Doppel Anastigmat. I had one of the last that was sold to me as a Dagor. Not a Dagor or a good lens. Dogmars, on the other hand, have a decent reputation. I'm quite pleased with my Dagorish lenses from other makers.

koh303
20-Jan-2015, 19:59
Peter, thanks for the kind words. I'm glad you saw that I didn't want to start a fight. You're right, no two of us have the same goals, consequently we see what our objectives do differently.

I hope you read far enough down the thread to find that the person who started the brawl ("my lousy 180 Dagor won't cover 8x10") sold 180 Dagors on eBay with claims that they covered 8x10. I found that hilarious. The biter bit, or, lies come home.

I've never really understood what Goerz' naming system for dialyte taking lenses for folding cameras tells us about the lenses. As I understand it Dogmars are better than Celors (which came first), which are better than Tenastimats and all the other ones whose names start with Ten-, which are better than the ones with no name but Doppel Anastigmat. I had one of the last that was sold to me as a Dagor. Not a Dagor or a good lens. Dogmars, on the other hand, have a decent reputation. I'm quite pleased with my Dagorish lenses from other makers.

perhaps you can take this discussion to the thread on which it belongs, and leave this topic on track?

Dan Fromm
21-Jan-2015, 08:38
koh303, thread drift is a fact of forum life. Live with it.

A propos of the Dogmar, the VM says:


Dogmar A new dialyt series was announced in Photography 26/05/1914, working at f4.5 in the shorter foci.
Since it was very late prewar, most examples will be postwar. Adverts. stressed it was a very highly corrected
lens, but the major sales feature was that it was separable, the front cell giving 2x focus, and the rear one 1.5x
focus. It was said to be free from ghosting, and the f4.5 was initially made in up to wholeplate size, the longer
sizes being in f5.5. It covers 55 or 54 at full aperture, and 60 at smaller apertures. It was suggested to use
21cm for 13x18cm plate. The f5.5 covered a slightly larger angle (54-60) and a slower version at f6.3 covered
a bit more again (60-65). However it was not primarily sold for its angle of cover, and the slower version was
short lived, being replaced by the Tenastigmats, etc.
The designer was W. Zschokke, and it was covered under Patent 258,494 and sold from 1914. It is sharper
than Celor, and shows better edge detail than the Q15 type designs. [Zschokke then left Goerz after the
association as Zeiss Ikon, and designed rather similar lenses for Kern, possible perhaps due to the take over
by Zeiss Ikon and the absence of this lens type in the Zeiss lists.]

Jim Galli
21-Jan-2015, 09:44
koh303, thread drift is a fact of forum life. Live with it.

A propos of the Dogmar, the VM says:

A lot of good useful info Dan. Thanks. BTW, what's in a name? Dogmar, Vomitar, Pukeon, so many good names never taken.

Nodda Duma
25-Jan-2015, 20:43
The US patent for the Dogmar is # 1,108,307 (search here: http://patft.uspto.gov/netahtml/PTO/patimg.htm ) . British patent is 833/13.

It's also mentioned in Kingslake's "History of the Photographic Lens", pg 100:

"...in 1916 the Celor was replaced by the f/4.5 Dogmar designed by w. Zschokke (1870 - 1951). An f/6.3 Dogmar was also manufactured for a short time."



It is of course a dialyte. I put the reported patent prescription in Zemax and it appears to be not quite as sharp as a Dagor would be but looks well enough. I can tell they intentionally vignetted the design to cover the 50 degrees. The performance really starts to drop off and would be pretty bad without vignetting (and you wouldn't be able to make lenses with realistic edge thicknesses unvignetted). Judging by the ray fans and spot size diagrams, this really should be a 30 degree lens. I bet Zschokke really corrected it for about 30 degree field of view and then the company opened up the field angles as much as possible before the aberrations got really bad. Beyond 30 degrees the spot size just kind of gets away from the lens.

Is lens flare present with this design? Looks like you'd get something close to a ghost focus off the second surface of the first negative element.

The lenses should be about 42mm diameter for the 180 f/4.5.

The as-reported prescription doesn't quite give good performance (even though the focal length is correct). To get good performance swap the two center glass types. I used SK4-LLF1-BAK4-SK4 from first to last lens (the patent reports SK4-BAK4-LLF1-SK4). That's probably what they changed when they applied for the patent to protect their actual product. Interestingly enough, you get slightly better performance by not swapping the two center glass types and instead letting the last glass type deviate slightly from that of the front element. So instead of SK4 (n=1.613), let it be SK14 (n=1.603). But I'm not sure SK14 was around then, so they wouldn't have been able to get this last bit of performance out. BAK4, LLF1 and SK4 were available tho I'm pretty sure. Anybody have a Schott glass catalog from the time period?

BTW all these glass types are now obsolete and were replaced by lead-free equivalents. LLF1 was never replaced, but Ohara S-TIL1 is an acceptable substitute when used with the new versions of the other glass in the prescription.

Not sure how this correlates with your experience with the lens or how it compares to others' analysis. Hope you don't mind the input...I've been accused of "drumming up business" lately which is ridiculous. I don't own a business and my employer has no interest in optics for the private sector. I do this for fun and I think people are interested in the insight. In actuality, this was a nice 10-minute distraction from some documentation I should be typing up for work. Back to the grind.