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Kasia Kesicka
11-Aug-2012, 12:24
Hi All,

This is my first post here although I've been reading the forum every now and then.

I have a Dallmeyer 3B lens that seem to be missing one of the rear elements. My knowledge is very limited so it could be the front one if its possible that the order of the lenses was changed; current rear element is glued to the body.

Obviously, I'd love to be able to use this lens for my alt processes work so I thought I'll ask around: does anyone have or heard of someone having other incomplete 3B that they will be willing to sell? Any advise where to look for one will be highly appreciated!

Thanks,
Kasia

maurits
11-Aug-2012, 12:40
Hi Kasia, good to see you over here too... :)

Finding that element will probably be an extreme long shot. But show us what you do have (carefully unscrew those lens elements) and the people here can tell you exactly what you are missing and -of course- what it is you are looking for.

If the rear element is really stuck, you could shine a torch light into it when the front is taken out and describe the reflections you see (how many, faint or dim).

It would be wonderful if you could complete your lens.

Cheers, Maurits

Kasia Kesicka
11-Aug-2012, 14:48
Hi Maurits,

Many thanks for your help here and on the Facebook group. I'll try to unscrew the rear element but it seems impossible without some tools. For now, few poor photos of the front element (group?) can be downloaded from here - https://dl.dropbox.com/u/7475217/3B_FrontElement.zip, whole lens & parts here - https://dl.dropbox.com/u/7475217/3B.zip

I don't have high hopes for finding the missing element but it would be silly not to try at least!

All the best,
Kasia

Kasia Kesicka
11-Aug-2012, 15:39
So.... we managed to determine that I'm missing the whole front group of my Dallmeyer 3B Patent lens. If anyone knows or will hear of other incomplete 3B that could help me get mine to working condition please let me know!

K

eddie
11-Aug-2012, 16:10
The whole front group? I can see the front group ( the cemented pair) in your first post/image.

I believe u r missing the dallmeyer FLINT lens.

Good luck. If u ever find one be sure to buy a lottery ticket as it will be your lucky day! :)

maurits
12-Aug-2012, 02:25
Eddie, it looks like someone stuck the rear flint up front. Even the little pin from the soft focus setting is visible... And then they shoe-horned the rear crown into the back and glued it... Unbelievable...

Maurits

alex from holland
12-Aug-2012, 03:08
Eddie, she's missing the front group for sure.
We did some photo exchange yesterday. The inner part of the back is mounted in the front.
The outer part of the back is glued at the back of the lens........ So they made a mess of it.

Alex

eddie
12-Aug-2012, 10:50
oh! now i am home and was able to open that zip file. amazing.....creative lens construction.

Steven Tribe
12-Aug-2012, 11:24
It is the rear pair which is unique factor in the soft petzval series from Dallmeyer - so it might be worthwhile looking for a suitable focal length front achromat that fits in the front thread. I doubt the performance of the "soft unit rear section" would be very different from the standard 3B although the overall optical characteristics will be different (unique). I have a couple of "lost" quality period front achromats, but nothing larger than the 2B size.
I had a similar problem - complete 3B cells, but no barrel - and I now have a working 3B! So you are quite well equiped, by comparison.

Kasia Kesicka
12-Aug-2012, 13:09
With a bit of patience and loads of alcohol I managed to free the rear element and put the whole group together as it should be. Thank you for your advise Steven, since finding real lenses may proof impossible I might look into doing just that!

Maurits and Alex - thanks again for all your help!

Steven Tribe
12-Aug-2012, 14:29
I don't have my 3B at home at the moment, but perhaps someone else can measure the sort of focal length you should be looking for in a front achromat?

alex from holland
13-Aug-2012, 12:37
Ok, now you have a almost working 3b
Now the search starts or sell this one in parts.

Steven, maybe your change to get an original 3b tube......



With a bit of patience and loads of alcohol I managed to free the rear element and put the whole group together as it should be. Thank you for your advise Steven, since finding real lenses may proof impossible I might look into doing just that!

Maurits and Alex - thanks again for all your help!

Steven Tribe
13-Aug-2012, 15:05
The thought did occur to me Alex.

But this is the older style - with focussing sleeve - but then again, the front achromat mounting might be the same in both versions.
2 new complete "3B"s would be better than just one with mixed parentage!

My new 3B is, by the way, making excellent wetplate images in Sweden at the moment.

Bruce Schultz
14-Aug-2012, 06:55
I have a 5A with a cracked front lens. Isn't there somewhere we could get new elements made?

E. von Hoegh
14-Aug-2012, 07:15
I have a 5A with a cracked front lens. Isn't there somewhere we could get new elements made?

New elements? Of course. But you'll find it less expensive to just get another lens. Grinding and polishing a one-off element will likely cost thousands, specialised tooling will have to be made for each surface which is ground and polished. But, it certainly is possible. I'm thinking of the man who spent roughly 30,000 GBP to have a new cylinder head made for a Rolls-Royce P3. At the time, the pound was exchanging for a bit over 2 USD.

Steven Tribe
14-Aug-2012, 09:44
It is quite possible to make a replacement achromat for a 3B or a 5A!

You need:

2 pieces of glass with the approximately correct size and refractive index. This quite ordinary crown and flint glass.

Knowledge of R1, R2, R3 and R4. This is the radius of the four surfaces where R2 is identical to R3 as it is a balsam join. These can be measured on an existing lens using a spherometer.

A home rigged vertical lathe with working area. 4 metal tools made to the surface diameters - convex for concave surfaces and vice versa. Various quantities of pitch and grinding/polishing compounds. Plenty of spit (used to keep the right dampness of the grinding mixture) and a copy of the book "Lens-work for Amateurs" by Henry Orford.

And lots of "hobby" time!

E. von Hoegh
14-Aug-2012, 10:13
It is quite possible to make a replacement achromat for a 3B or a 5A!

You need:

2 pieces of glass with the approximately correct size and refractive index. This quite ordinary crown and flint glass.

Knowledge of R1, R2, R3 and R4. This is the radius of the four surfaces where R2 is identical to R3 as it is a balsam join. These can be measured on an existing lens using a spherometer.

A home rigged vertical lathe with working area. 4 metal tools made to the surface diameters - convex for concave surfaces and vice versa. Various quantities of pitch and grinding/polishing compounds. Plenty of spit (used to keep the right dampness of the grinding mixture) and a copy of the book "Lens-work for Amateurs" by Henry Orford.

And lots of "hobby" time!

Quite correct. Many amateurs have succesfully made telescope mirrors.
However it is nowhere near as simple as you make it sound. It takes time, knowledge, and experience to acquire the neccesary skills. A telescope mirror is relatively simple, you don't have two vertices of polished surfaces to keep in line, nor do you have two spherical surfaces to keep in perfect alignment. You also need to edge the finished lenses accurately enough to mount in the existing objective while keeping them perfectly centered.. You need at least three polishing tools for each radius: roughing, finishing, polishing, then you switch to pitch in another metal holder for the final polishing, and you need the tools to make the polishing tools - a metal lathe with a very accurate sphere turning attachment, plus the skills to use it. I've looked into this with the idea of making my own long focal length Dagor. It's certainly doable. But it's just as certainly not for the faint hearted.

Kasia Kesicka
15-Aug-2012, 05:36
Quite correct. Many amateurs have succesfully made telescope mirrors.
However it is nowhere near as simple as you make it sound. It takes time, knowledge, and experience to acquire the neccesary skills. A telescope mirror is relatively simple, you don't have two vertices of polished surfaces to keep in line, nor do you have two spherical surfaces to keep in perfect alignment. You also need to edge the finished lenses accurately enough to mount in the existing objective while keeping them perfectly centered.. You need at least three polishing tools for each radius: roughing, finishing, polishing, then you switch to pitch in another metal holder for the final polishing, and you need the tools to make the polishing tools - a metal lathe with a very accurate sphere turning attachment, plus the skills to use it. I've looked into this with the idea of making my own long focal length Dagor. It's certainly doable. But it's just as certainly not for the faint hearted.

Sooner or later due to demand someone will be offering such services, for sure though at the high price. Exciting as it sounds, making my own cells requires specifically what I don't have (knowledge, tools and time). For now I'll keep my eyes open for another incomplete 3B or a suitable focal length front achromat that will fit in the front thread as advised by Steven earlier in this thread.

Steven Tribe
15-Aug-2012, 06:54
I don't like to be pessimistic, but I think the chances of increasing availability of specialised lens replacement services is zero.
Recent decades have seen the demise of all sorts of similar speciality services. Even in the field of vintage car restoration services, which attracts more people than we do, there are fewer people/companies and these run on very commercial principles!

The days of the Gentleman (woman) amateur who used hours each day on their hobby (alchemy, astronomy, photography, golf etc.) has gone for ever. The emancipation of women, absence of domestic staff, contractual employment and the falling comparitive incomes of the middle case compared with artisans, have all contributed.

E. von Hoegh
15-Aug-2012, 07:02
I don't like to be pessimistic, but I think the chances of increasing availability of specialised lens replacement services is zero.
Recent decades have seen the demise of all sorts of similar speciality services. Even in the field of vintage car restoration services, which attracts more people than we do, there are fewer people/companies and these run on very commercial principles!

The days of the Gentleman (woman) amateur who used hours each day on their hobby (alchemy, astronomy, photography, golf etc.) has gone for ever. The emancipation of women, absence of domestic staff, contractual employment and the falling comparitive incomes of the middle case compared with artisans, have all contributed.

The demise of the Gentleman enthusiast/amateur was a while ago, it coincided with the demise of the independently wealthy class. It's a real shame, too, because there was quite a bit of very good science done by these folks.

There are still some left, look up Duncan Pittaway who is restoring one of the two Fiat S76 LSR cars from a frame and an engine. There are others in various fields.

goamules
15-Aug-2012, 12:23
If there was enough demand, there are optical companies that could make a modern petzval. But there isn't enough demand, no company is going to start making a specialty large format lens that might sell 10 a year. The same skilled craftsman and one-man business that could make you a one-off replacement element could make complete lenses. But both would be very expensive.

alex from holland
15-Aug-2012, 12:47
I am sure there's a market for these new lenses
Large format photography is hot. Not alone wet plate, but polaroid, film etc.
People are even looking for petzvals for the medium format digital camera's

pbryld
15-Aug-2012, 14:02
I am sure there's a market for these new lenses
Large format photography is hot. Not alone wet plate, but polaroid, film etc.
People are even looking for petzvals for the medium format digital camera's

I think the notion that LF and wet plate is "hot" is simply an illusion that comes from being on these forums. It makes it seem like everyone is doing it, that it's quite normal, but in reality, it's still a very unique thing to do that will set you apart from most other photographers in the world.

goamules
15-Aug-2012, 18:48
I think the notion that LF and wet plate is "hot" is simply an illusion that comes from being on these forums. It makes it seem like everyone is doing it, that it's quite normal, but in reality, it's still a very unique thing to do that will set you apart from most other photographers in the world.

I concur. Though a lot of large brass lenses sell on Ebay, a lot of those buyers are now investment speculators, not users. If you want a close approximation of how many people might buy a newly made lens (if the price was below that of an old one), look at how many large format cameras are made and sold each year. Not many, I would guess. Or perhaps a better guage; how many of the "replica Pinkham & Smith" Cooke PS945 lenses sold when they started making them a few years ago?

alex from holland
16-Aug-2012, 14:18
Garrett, these is also a shortage on affordable wet plate camera's ( over here)
There are only 1 or 2 suppliers in Europe and a handfull in the US. Shipping to Europe is a pain in the ass.
Huge shipping costs and we have to add about 25% taxes and custom fees.
Waiting lists of more than half a year is "normal"
Many of my wet plate "students' are looking for an affordable solution of a lens and wet plate camera.
I am sure if someone was able to produce a 3b copy it would sell for about 1500,=. And it even wouldn'tneed a rack and pinion as nobody is using that.

Alex

vitality
17-Aug-2012, 03:12
I'm not sure that somebody would buy new petzval for 1500... You can find 3B for same price (even cheaper, few days ago was sold for 1000eur on eBay), so why to buy alternative? Need urgently to start shooting? You can find some Hermagis F4 for 500 eur. Not the same, not F/3, without SF adjustment, but do you need it from the 1st day of shooting, or for first few months it would be a good lens?
If you buy 3B and in 2-3 years you stop shooting, you will sell it for same money (+/-? may be you will make some profit, may be you will lose something). Buying new alternative, means losing money when you sell it later (why would someone buy used one for 1500 if new one is available for the same price. Apart of situation, that everybody wants this lens, and to buy new one you need to wait for 2-3 years, so you ready to pay some amount for used one just to gt it today). I'm not talking about buying/selling only because of profit, I'm saying about not loosing money if you decide to sell it later, because you stop shooting.

Well, that's my opinion, I might be wrong...

goamules
17-Aug-2012, 10:22
I mostly agree with Vitality, but I hear your points too Alex. I think the two factors are 1) supply and demand, and 2) cost of a replica. Two items I'm very familiar with that are replicated are guns and string instruments. Back in the 1970s you could buy an original Sharps "buffalo rifle" for about $1200. Because of a new target shooting sport in America, the prices started going up until a good one was $3,000 - $5,000 in the late 1980s. At that point, and after the movie Quigley Down Under, Shiloh Sharps started selling more of their replicas. At that time they were about $1,000. So 1/3 to 1/5 the cost of an original.

The best Mandolins are Gibsons from the 1910s to 1930s. For a brief period in the 1920s a genius named Loyd Loar made the best Gibson ever made. Loar signed Gibsons sold for around 3,000 in the 1980s (a regular Gibson from the 20s would be about $500). By 2000, a Loar mandolin cost about $15,000, and a company in China (yes, China) started hand making very good Loar-style mandolins for about $700. I think they cost about a grand now. Again a 1/5 to 1/15 cost replica.

Both of the above companies are doing very well, and their replicas are still in much demand. I think there are less LF photographers than antique target rifle shooters or even mandolin players. But whatever the demand is, a replica 3B would have to cost much less than the average price of an original. We know what an original costs right now, on average. What would tip someone in the favor of a replica 3B? Not the current original cost.

alex from holland
17-Aug-2012, 11:23
Nobody has a wrong opninion !
But where do you find a hermagis f4 for 500,= ? You may pm me for that is i collect the hermagis lenses!
There also has been sold a 3b for more than 2000 usd just a few days ago. so 1000 is rather a bargain. ( they still exist though.....)

I always wondered why people buy new gear. I ALWAYS bought mine used and that saved me a lot of money.
But go out and have a look at the large camera stores. People are spending money like crazy on new gear for : new gear.
The majority doens't want to buy used gear.
They want it new. Like new cars, news camera's, new clothes, new girlfriends.
Oeps, forget about the last option..... That will cost a lot of money LOL





I'm not sure that somebody would buy new petzval for 1500... You can find 3B for same price (even cheaper, few days ago was sold for 1000eur on eBay), so why to buy alternative? Need urgently to start shooting? You can find some Hermagis F4 for 500 eur. Not the same, not F/3, without SF adjustment, but do you need it from the 1st day of shooting, or for first few months it would be a good lens?
If you buy 3B and in 2-3 years you stop shooting, you will sell it for same money (+/-? may be you will make some profit, may be you will lose something). Buying new alternative, means losing money when you sell it later (why would someone buy used one for 1500 if new one is available for the same price. Apart of situation, that everybody wants this lens, and to buy new one you need to wait for 2-3 years, so you ready to pay some amount for used one just to gt it today). I'm not talking about buying/selling only because of profit, I'm saying about not loosing money if you decide to sell it later, because you stop shooting.

Well, that's my opinion, I might be wrong...

Steven Tribe
18-Aug-2012, 06:44
I really don't know whether the estimated price of 1,500 usd is realistic for a batch production of new 3D lenses.

I just have no idea whether modern lens production technology has reached a stage where preliminary forming of surfaces, diameter and depth can be made on a programmed lathe/grinder set-up? If this is the case, then perhaps final polishing and assembly could be made by the purchaser? I believe this is the system employed by amateur telescope makers buliging their own mirrors.

Comments from someone who has knowledge of the present technology of optical lens production would be appreciated?

E. von Hoegh
18-Aug-2012, 07:11
I really don't know whether the estimated price of 1,500 usd is realistic for a batch production of new 3D lenses.

I just have no idea whether modern lens production technology has reached a stage where preliminary forming of surfaces, diameter and depth can be made on a programmed lathe/grinder set-up? If this is the case, then perhaps final polishing and assembly could be made by the purchaser? I believe this is the system employed by amateur telescope makers buliging their own mirrors.

Comments from someone who has knowledge of the present technology of optical lens production would be appreciated?

Batch production prices would depend mostly on the size of the batch. I think $1500 is low.
As for selling partially finished elements and a barrel to assemble, how many photographers also have the skills to do this? How many are even aware of what skills and tools are needed? Damn few. This approach sounds like a potential disaster due to the almost infinite variety of pitfalls, and the price of the kit would still be high. The CNC technology does exist to rough out elements though.

As I pointed out in a previous post, making a telescope mirror (one surface) and making a photographic objective are vastly different.

Steven Tribe
19-May-2013, 11:52
I have started this thread again as I have discovered a 3B, with a missing final rear element, but in a rear-turn barrel and complete front achromat.
Commercial organisation in London. Price would be cheaper than getting this achromat made. Alternatively, you could sell them the ajustable rear lens?
I have sent a PM.

Steven Tribe
21-May-2013, 14:27
I can, with great pleasure, reveal that Ms. Kasia Kesicka will be receiving the front achromat and hood within a few days.
And I will be taking over some other parts of a 3B that I can use.

Kasia Kesicka
21-May-2013, 15:25
Indeed :) Thank you very much Steven for all your help and remembering about my 'mission impossible'!



I can, with great pleasure, reveal that Ms. Kasia Kesicka will be receiving the front achromat and hood within a few days.
And I will be taking over some other parts of a 3B that I can use.

Tim Meisburger
21-May-2013, 18:32
Okay, but after this odyssey, I demand pictures of the children of this union (when available).

Congrats to all!

Amedeus
21-May-2013, 18:54
Talk about finding a needle in a haystack ... happy ending ... great !

Steven Tribe
21-May-2013, 23:46
needle in a haystack
Not quite as difficult! The 3B must have been the major seller of the series for 50 years or so.
The availability of a single correct lens is impossible - a big achromat might have come from any lens. But getting hold of another incomplete 3B from the same detailed design - with the missing part intact - is by no means impossible. Putting a price on an incomplete lens (and getting it accepted!) and co-ordinating takers for some of the other parts, is difficult.

maurits
23-May-2013, 00:02
Congrats Kasia and well done Steven!

Steven Tribe
17-Jun-2013, 14:18
The conclusion of this fairy tale has been a bit delayed thanks to MW's loose packing and problems between Her Majesty's Post office and Irish Mail.

I received a caved-in barrel from the 3B plus the fixed rear lens and a full set of Waterhouse stops.
Kasia got the replacement front achromat with the "big" style lens hood after over a week in the Post.

I managed to round-up the barrel (hardwood shapers) so it accepts my front achromat.

Kasia found her achromat just went in like magic.
I have made some Waterhouse stops in brass for her.
I'll post a picture of mine when I have finished re-doing the balsam. Kasia, I'm sure, will post her's when she gets a bit of time.

Nice that Dallmeyers standards were so good that a few decades between production doesn't mean anything.

VPooler
17-Jun-2013, 15:08
For future reference, one can obtain lenses from www.surplusshed.com
They carry a lot of odd and rare glass. Anything from single elements to whole assemblies. Next time you are missing a lens, try to find out the focal length and diameter and search it there. I've gotten some odd bits for my contraptions there. They also carry Wollensak and Jaegers glass.

Steven Tribe
17-Jun-2013, 15:20
No doubt you can get a workable achromat for a simple landscape lens with character, but to think that you can a replacement lens for any Petzval at Surplus Shed is just not correct.

Vincent Pidone
17-Jun-2013, 16:04
Steven, you're right of course, but...

I seem to recall that Surplus Shed offers to custom make lenses in small batches to the users' specifications, so:

What if we ask what it would cost to duplicate one of the most popular lens designs (a 3B maybe?) ?

Someone would have to come up with the glass for them to measure before they could come up with a quote.

I kind of wonder why Rhinehold doesn't try to do this, he's 1/3 of the way there already.

VPooler
18-Jun-2013, 00:14
No doubt you can get a workable achromat for a simple landscape lens with character, but to think that you can a replacement lens for any Petzval at Surplus Shed is just not correct.

You never know what you might find :P

Steven Tribe
18-Jun-2013, 00:47
What would be more useful would be an up-to-date register of incomplete lenses and parts.

These are so special that it requires guts to list them in the Wanted/ For Sale.

From memory, I have, for example ( and only as an example), the following items which would almost certainly not find a buyer but might make someone's day, sometime.

1. Ross/Goerz series III 5" Barrel - for someone has the cells.
2. Ross/Zeiss F6.3 140mm - for someone who has the cells - plus can repair the iris.
3. Dallmeyer 3B rear turn barrel. Lost identity on shortened sleeve. But it would contribute to a workable lens.
4. Dallmeyer 3B inner (fixed) rear cell. This is a simple lens which is well protected from damage/loss - but you never know.

VPooler
18-Jun-2013, 03:10
Steven, you're right of course, but...

I seem to recall that Surplus Shed offers to custom make lenses in small batches to the users' specifications, so:

What if we ask what it would cost to duplicate one of the most popular lens designs (a 3B maybe?) ?

Someone would have to come up with the glass for them to measure before they could come up with a quote.

I kind of wonder why Rhinehold doesn't try to do this, he's 1/3 of the way there already.

This needs to happen. I believe they might have a lot of the necessary lenses for recreations in stock and if only a few custom parts are needed, the price can be quite affordable. I have thought of making a Petzval myself in the far future. Someone who lives in the states, possibly near them ought to have a talk with them.

goamules
18-Jun-2013, 06:08
You should understand the grind curves and refractive indexes of each piece of glass is matched to the other pieces of glass in individual lenses. Just grabbing a "double convex" or "achromat doublet" that happens to be in a box of glass and trying to get an optimal image from a 1902 Dallmeyer or 1858 CC Harrison (I have one missing the rear glass) is not going to work. Each piece is mated to the others. Will you get an image? Yes, but it will not be a Dallmeyer or CC Harrison image. Petzvals might be easier than some, but the problem with them is they changed over time (the Lerebours color correction was just one modification) and each manufacturer had slightly different modifications. Petzvals were made from 1840 to 1940 , and they're all slightly different. Their glass is not like out of a cookie cutter.

Steven Tribe
18-Jun-2013, 06:49
Which, of course, is why an earlier thread pointed out all the problems in great detail.

English lenses used the glass available from Chance Bros. and French makers used SGO or St. Gobain. Even when Jena glass made new glass products around 1890 (basically higher refractive indices), each major lens maker was able to order glass (refractive index) which suited their existing designs or specific new products.
This prosed new production is only possible with combinations of simple lens where the refractive index is the same.

Steven Tribe
7-Jan-2017, 03:30
I thought I would up-date this as there has been a project in the Colloidion Bastards group relating to the remanufacture of the Dallmeyer. I can't see any recent information on their site, but a certain number were made for evaluation. What is most relevant here, though, is the fact that it was found that the glass used in the Dallmeyer Patent Portrait series is unobtainable and that "alternatives" were employed. I have no knowledge of how satisfactory the results have been, other than there are differences!

Part classical lenses seem to be offered for sale quite regularly at the moment (perhaps due to shortage of the regular items?) and I have seen listers who insist that missing lenses can be replaced by "Ordering" them somewhere. These part lenses always seem to be missing the complex brass mountings and really only have the value of the intact lenses in their cells.

Steven Tribe
7-Jan-2017, 03:48
You should understand the grind curves and refractive indexes of each piece of glass is matched to the other pieces of glass in individual lenses. Just grabbing a "double convex" or "achromat doublet" that happens to be in a box of glass and trying to get an optimal image from a 1902 Dallmeyer or 1858 CC Harrison (I have one missing the rear glass) is not going to work. Each piece is mated to the others. Will you get an image? Yes, but it will not be a Dallmeyer or CC Harrison image. Petzvals might be easier than some, but the problem with them is they changed over time (the Lerebours color correction was just one modification) and each manufacturer had slightly different modifications. Petzvals were made from 1840 to 1940 , and they're all slightly different. Their glass is not like out of a cookie cutter.

I think these are very wise words, also in retrospect!
I have "played around" with quite a few "parts" lenses since this thread was active and have some conclusions.

Mixing the front achromats/rear cells from different periods of Dallmeyer 3b does work. That is, within the rear unscrew and front turn models. The rear cells have at least two different designs (internal thread sizes), so this section (a pair) has to from the same lens.

Using a "foreign" achromat to repair a "beloved" Petzval does work if the focal length is near the original and you have possibilities for fine adjusting the distance between the cells. Replacing the rear pair is probably a very frustrating exercise, with little chance of success.

Amedeus
9-Jan-2017, 13:44
As Garret and Steve have stated, it is not that simple.

There seems to be little appreciation for the fact that the old glass is simply no longer available and even fewer know that even with modern glass, there are differences from batch to batch.

This means that one has to update the design each and every time the glass changes composition. There is more to glass than refractive index ...

And matching the front cell with modern glass to the rear cell of historic glass is just not going to cut it if one wants the same optical characteristics.

When the company I'm a CTO for acquired Rodenstock few year back, I enthusiastically approached the Rodenstock engineering team to whip me up a Ronar APO 1800mm ... lol ... after all, they might have a few parts still around ? Got an internal quote of $500K to redesign the glass, produce all needed tooling and they would deliver 10 lenses. Extra lenses would be $15k each.

So no, in spite of all experimenting with glass out of the toolbox, high hopes, fingers crossed ... as soon as good enough is not good enough, exact duplication is not easy and cost real money.

YMMV,

Cheers,

Rudi A.


Steven, you're right of course, but...

I seem to recall that Surplus Shed offers to custom make lenses in small batches to the users' specifications, so:

What if we ask what it would cost to duplicate one of the most popular lens designs (a 3B maybe?) ?

Someone would have to come up with the glass for them to measure before they could come up with a quote.

I kind of wonder why Rhinehold doesn't try to do this, he's 1/3 of the way there already.

Bernice Loui
10-Jan-2017, 01:34
Optical glass batches are cast with a mould area for a test prism. This test prism is used to test that specific batch of optical glass for expected specifications. Due to recent CE requirements, some ingredients once used in optical glass manufacturing can no longer be used adding another layer of difficulty to produce vintage optical glass.

Creation of a replacement lens element is only the beginning. How does one ascertain proper match and performance of the replacement lens element. Most if not all optics created during this era were hand ground, hand matched, hand assembled-tested and assessed for proper performance by highly skilled experts at their craft.

The lens might function, question is does the lens function as intended by the individual or folks who designed the lens, this is no small difference.



Bernice



As Garret and Steve have stated, it is not that simple.

There seems to be little appreciation for the fact that the old glass is simply no longer available and even fewer know that even with modern glass, there are differences from batch to batch.

This means that one has to update the design each and every time the glass changes composition. There is more to glass than refractive index ...

And matching the front cell with modern glass to the rear cell of historic glass is just not going to cut it if one wants the same optical characteristics.

When the company I'm a CTO for acquired Rodenstock few year back, I enthusiastically approached the Rodenstock engineering team to whip me up a Ronar APO 1800mm ... lol ... after all, they might have a few parts still around ? Got an internal quote of $500K to redesign the glass, produce all needed tooling and they would deliver 10 lenses. Extra lenses would be $15k each.

So no, in spite of all experimenting with glass out of the toolbox, high hopes, fingers crossed ... as soon as good enough is not good enough, exact duplication is not easy and cost real money.

YMMV,

Cheers,

Rudi A.