Repro-Claron f/9 210 mm

[Greg Lockrey]

I acquired this lens for payment for printing from a "starving artist" client. (I get a lot of equipment this way.) Has a Copal 0 shutter that in great shape. I was wondering if any of you tech types can tell me anything about this lens other than it's a "flat field" used for copy work. What are the effective magnifications and/or could this be effective for photographing large areas like murals? My guess this one was made in the early '60's. It came with a Calumet monorail with a 24" bellows 4x5 camera that needs a little tlc if someone needs it. I plan on keeping the lens.

[Dave_B]

You may or may not know that the Repro-Clarons are mildly radioactive. Thorium was used in making the glass. There are a number of posts here that talk about this. Appropriate care in storage is advised.
Dave B.

[Greg Lockrey]

I seen that in my research. I was wondering if they all were and how much? Being that I'm already 60, how long will it take to kill me? :eek:

[Kevin Crisp]

Look through the lens at a white piece of paper. If you see tea-colored discoloration you have a hot one. Treatment over several weeks with a strong UV light (I used the Feit brand 15 compact florescent bulb) will essentially eliminate that. Schneider has serial number ranges and dates on their web site if you want to find the date of production.

I have your lens and the 305 and two longer versions. The 305 screws into a Copal 2 shutter and I front mount the longer ones on the same. I use mine for general landscape photography. They are exceptional performers. They do not have the coverage of the G Clarons but they are very useful within their limits. The 210 covers 4X5 at infinity with lots of room for movement, the 305 is terrific for 5X7. A 210 lens in a copal 0 with performance like that is very useful. I am sure they are wonderful for close ups and artwork but since I do neither I can't speak from personal experience. The 210 is most often used on my Crown Graphic since it is so small and light.

[Greg Lockrey]

In a bright light it looks slightly yellow, but hardly noticable. Serial number puts it between Jan-Oct of '67. The previous owner used it to make transperencies of architectural renderings.

[Kevin Crisp]

It's an early one and probably radioactive. Serial number somewhere around the 9's?

[Greg Lockrey]

It's an early one and probably radioactive. Serial number somewhere around the 9's?

10 235 xxx

[Jim Galli]

In coverage and sharpness they act very like a Goerz RD Artar. They have one benefit over the Artar. It is the most compact 210mm lens in existence. The next closest rivals are the 203 Ektar, same general design but slightly faster, and the Nikkor M 200mm.

[Ernest Purdum]

It's a fully symmetrical dialyte lens. four individual elements. Schneider rated the angle of view at only 48 degrees, bui the 210 still gives room for movements on 4" X 5".

It was intended for more than just copy work. It was optimized for close-up work in the range 1:10 to 10:1, very good for product photography and the like, but not limited to that range. The dialyte type is well known for working well at a large range of subject:image ratios, even to infinity.

You will sometimes see "flat field" referred to as though there were some characteristic keeping process lenses from being used to photograph three-dimensional subjects. I don't know of any lens characteristic of this nature.

[Greg Lockrey]

Thanks all, this was the kind of information that I was looking for.

[Phil]

Greg,

From the archives - lots of good info. (in German)

http://www.schneiderkreuznach.com/archiv/pdf/repro_claron.pdf

I've got a 485 - also f/9 - and it's a huge hunk of glass.

Phil

[Greg Lockrey]

Greg,

From the archives - lots of good info. (in German)

http://www.schneiderkreuznach.com/archiv/pdf/repro_claron.pdf

I've got a 485 - also f/9 - and it's a huge hunk of glass.

Phil

Thanks Phil, I actually got through with some of it with the diagrams. :)

[Mark Tweed]

Greg, I have this same 210, close to the same year of production as yours - I also have the 420mm version. These are superb lenses. I use them for landscape work and they fantastic for that, sharp like an Artar and incredibly compact for their focal length. I have the Kodak 203mm Ektar and a 270mm RD Artar and these dialyte designs, like the Repro Claron are stellar performers.

I'll sacrifice the slower f stop speed and coverage of these lenses in preference for their smaller size and weight over the traditional f5.6 Plasmat designs, because I backpack often with my large format systems. They're perfect for my field use.

Enjoy your new lens.


Mark

[Pete Watkins]

I have used my one with a front mounted Copal/Polaroid 1 shutter to capture a few portraits on 4x5, and the sharpness of the image is stunning. Sharp as a razor.
Pete

[Mark Sampson]

Somewhere on this site, in another thread about this lens, it was suggested that the Repro-Claron went away after Schneider aquired the rights to the Goerz designs and names. After that Schneider produced the Apo-Artar line, which had the advantage of a more famous nameplate and no thorium glass, until the early 1990's. I can't say if that's true, but it seems plausible.

[walter23]

I don't think you have to worry about the radioactivity unless you grind it up and breath it in, or eat it. I think thorium is an alpha emitter, which means the radiation can barely get more than an inch through the air, and won't even get through your skin.

[Greg Lockrey]

I don't think you have to worry about the radioactivity unless you grind it up and breath it in, or eat it. I think thorium is an alpha emitter, which means the radiation can barely get more than an inch through the air, and won't even get through your skin.

Thanks, it doesn't matter at my age. It would take too long to kill me and I would probably be already dead by then anyway. :eek: :D

There has been some interesting tidbits of information about this class of lenses.

[Arne Croell]

Somewhere on this site, in another thread about this lens, it was suggested that the Repro-Claron went away after Schneider aquired the rights to the Goerz designs and names. After that Schneider produced the Apo-Artar line, which had the advantage of a more famous nameplate and no thorium glass, until the early 1990's. I can't say if that's true, but it seems plausible.
There was some overlap for a few years - Schneider acquired Goerz in 1972 and the Repro-Claron was made until at least 1978/79 (I have a 305mm/12" Repro-Claron with serial no. 13504xxx, that is a production date between 1978 and 1979). That lens, btw, is not radioactive, Schneider changed the design in the mid-seventies, compare this older thread: http://www.largeformatphotography.info/forum/showthread.php?t=25457&highlight=repro-claron+radioactive
One question in my mind is - when the Repro-Claron ceased to exist, was the later Schneider Apo-Artar design the same as the previous Apo-Artar or the last version of the Repro-Claron under the better known name? Or another redesign?

[Michael S. Briggs]

I don't think you have to worry about the radioactivity unless you grind it up and breath it in, or eat it. I think thorium is an alpha emitter, which means the radiation can barely get more than an inch through the air, and won't even get through your skin.

It is true that natural thorium, Th-238, is an alpha emitter, but Th-238 decays into a series of radioactive isotopes, which together emit a mixture of radiations, including gamma-rays. The Thallium-208 daughter emits a 2.6 MeV gamma-ray. The gamma-rays are much more penetrating the the alpha particles. One might as well minimize the radiation dose to people by keeping lenses with Thorium glass at a distance when not in use.

[Greg Lockrey]

It is true that natural thorium, Th-238, is an alpha emitter, but Th-238 decays into a series of radioactive isotopes, which together emit a mixture of radiations, including gamma-rays. The Thallium-208 daughter emits a 2.6 MeV gamma-ray. The gamma-rays are much more penetrating the the alpha particles. One might as well minimize the radiation dose to people by keeping lenses with Thorium glass at a distance when not in use.

Just so you know Michael, Water and I are political antagonists. :eek:


Just KIDDING, Walter! :D :D

[Ole Tjugen]

It is true that natural thorium, Th-238, is an alpha emitter, but Th-238 decays into a series of radioactive isotopes, which together emit a mixture of radiations, including gamma-rays. The Thallium-208 daughter emits a 2.6 MeV gamma-ray. The gamma-rays are much more penetrating the the alpha particles. One might as well minimize the radiation dose to people by keeping lenses with Thorium glass at a distance when not in use.

Natural Thorium is 232Th which decaus to Radium 228 by alpha emission. Since the half life of 232Th is 1.405×10^10 years and that of 228Ra is 6.7 years, we can safely assume there is no Radium in the glass. The next step is Actinium, 228Ac by beta emission. And so on and on down to lead...

But since the parent isotope, 232Th, is the most stable isotope in the chain, the vast majority of the radioactivity will be from that first step - and the radiaoctivity will decrease over time. Yes, Thallium 208 is formed in one of the two possible paths just before the end, but all that means is that you shouldn't sleep with the lens under your pillow - or crush it and inhale the dust.

To the best of my knowledge there is no such isotope as Thorium 238.

[Jiri Vasina]

I'll take it from the last:

Ole, there is a Thorium 238 isotope, but the only info I found about it is that it has a half-life of 9.4minutes. Not it's decay chain. (wikipedia).

Further calculations might be wrong (I might have a mistake somewhere), but I believe they are not fundamentally wrong:

The amount of radioactivity in thorium 232 is negligible - if it has a halflife on the order of 10^10 years, that means that in 1kg of pure Thorium 232 one radioactive decay every 1010 minutes - that is almost every 17hours between that. At that moment a Radium 228 is created, which is a beta emitter with half-life of 6.7 years - again, that means that every minute it has a 0.0000197% chance of decaying - a chance you would in other situations consider negligible.

And that is only speaking of time. If you also consider the aspect of space and all the possible directions the generated particle can travel in, the chance of the particle hitting your body is even less (by orders).

The long half-life of the mother isotope also means (and short half-life of the dangerous isotopes like all the beta emitters (there are no gama) 228Ra, 228Ac), that the equilibrium state achieved is one with very low amount of those dangerous particles. And the resulting radioactivity is very low.

I hope the above is at least a bit clear.

(I think that a chance of being asked for a date with the most-beautiful and most-intelligent lady you have met in the past year - and asked by her - is more likely than waiting for this single radioactive decay chain to hit you with any significant effect).

Tomorrow I'll take my 305mm Repro-Claron (S/N 8,xxx,xxx) to work and measure if any radiation is detectable (not-alpha. Have no means to detect that).

[Arne Croell]

A 355mm Repro-Claron I own (serial no. 85xxxxx) is good for about 9 µSv/h (micro-Sievert/hour) of just gamma radiation next to the front or back element; background radiation here is about 0.15µSv/h, so its about 60x higher than background.

[Jiri Vasina]

So I must have forgotten something important :eek:

That's yet more reason for me to take my 305mm Repro-Claron for a measurement tomorrow...

[Ole Tjugen]

It's possible that the Thorium in the glass is about as pure as that in a sample of Thorite I measured at one time - 0.8 millisievert/hour is quite a bit above "background". It's even far above the background where I found it! :)

[Greg Lockrey]

:eek: :eek: :eek:

[Michael S. Briggs]

Natural Thorium is 232Th which decaus to Radium 228 by alpha emission. Since the half life of 232Th is 1.405×10^10 years and that of 228Ra is 6.7 years, we can safely assume there is no Radium in the glass. The next step is Actinium, 228Ac by beta emission. And so on and on down to lead...

But since the parent isotope, 232Th, is the most stable isotope in the chain, the vast majority of the radioactivity will be from that first step - and the radiaoctivity will decrease over time. Yes, Thallium 208 is formed in one of the two possible paths just before the end, but all that means is that you shouldn't sleep with the lens under your pillow - or crush it and inhale the dust.

To the best of my knowledge there is no such isotope as Thorium 238.

Yes, I mis-typed when I wrote 238 instead of 232.

But it isn't safe to assume that there is no radium in the glass or that the vast majority of the radioactivity comes from the first step. Because of the long half life of Th-232, the amount of Th-232 in the glass is almost constant and it is producing Ra-228 at an almost constant rate. Ra-228 has a half life of about 6 years, much shorter than the age of any lens with thorium glass. This means that there has been enough time for the Ra-228 content to reach its equilibrium value, which is not zero. In fact, all of the radioactive daughters in the decay chain have short half lives compared to the age of these lenses, so they have all reached their equilibrium concentrations, all the way down to the final radioactive daughter, Tl-208. Tl-208 is the isotope that emits the 2.6 MeV gamma-ray. If you don't believe this reasoning, take a gamma-ray spectrum of a lens with thorium glass, as I have -- you will observe the 2.6 MeV line.

[Michael S. Briggs]

I'll take it from the last:

Ole, there is a Thorium 238 isotope, but the only info I found about it is that it has a half-life of 9.4minutes. Not it's decay chain. (wikipedia).

Further calculations might be wrong (I might have a mistake somewhere), but I believe they are not fundamentally wrong:

The amount of radioactivity in thorium 232 is negligible - if it has a halflife on the order of 10^10 years, that means that in 1kg of pure Thorium 232 one radioactive decay every 1010 minutes - that is almost every 17hours between that. At that moment a Radium 228 is created, which is a beta emitter with half-life of 6.7 years - again, that means that every minute it has a 0.0000197% chance of decaying - a chance you would in other situations consider negligible.

And that is only speaking of time. If you also consider the aspect of space and all the possible directions the generated particle can travel in, the chance of the particle hitting your body is even less (by orders).

The long half-life of the mother isotope also means (and short half-life of the dangerous isotopes like all the beta emitters (there are no gama) 228Ra, 228Ac), that the equilibrium state achieved is one with very low amount of those dangerous particles. And the resulting radioactivity is very low.



Tomorrow I'll take my 305mm Repro-Claron (S/N 8,xxx,xxx) to work and measure if any radiation is detectable (not-alpha. Have no means to detect that).


I have measured many lenses with thorium glass. Over a 2 inch diameter Geiger detector the count rate is typically at least thousands per second, not approximately one per day.

Yes, the Wikipedia article lists only alpha and beta decay modes for the Thorium series. But that leaves some things out -- some of the resulting nuclei are created in excited states that emit gamma rays to reach their ground state. Also the electrons of the new atom will frequently reach their ground state by emitting x-rays. If you take a x-ray / gamma-ray spectrum, you will observe many lines.

[Jiri Vasina]

After sleeping relatively well, I also know that I have forgotten the gamma rays. I know that there are (almost) no natural pure alfa- or beta-only emitters, everyone of them also emits gamma. And I have forgotten that yesterday evening.

[Jiri Vasina]

:eek: :eek: :eek:

I have just measured my 305mm Repro-Claron and at the front and rear of the glass (less than 1cm from the surface), the flow is at 9µSv/h (as measured by Arne).

But at 10cm from the glass, it has already fallen to 0.9-1µSv/h. And when measured on the sides of the barrel (where the barrel serves as shield) touching the lens barrel the flow is at 2-2.5µSv/h.

When I took the lens apart, the radioactive one is the frontmost glass in the front element, and the rear-most in the rear element (both the entrance and exit ones).

I don't have a spectrometer at hand, so I believe you with the spectral characteristics.

:eek:

[Greg Lockrey]

OH NO!!! :eek: :eek: :eek: We're gonna die!

[Jiri Vasina]

No. I have just made further measurements.

It means that you should minimize your (tactile) contact with the lens - especially with the glass itself - to minimize irradiation of your hands.

When the lens is used, my 305 Claron is around 30cm from the ground glass, when composing, my eyes are around 20-30cm from the ground glass. My measured radioactive flow at 50cm from the lens (in clear air, without the intervening groundglass) is at the background rate 0.1-0.2µSv/h. So the dose to the eyes when used normally for normal composing/focusing time is negligible.

Also the flow at the side of the lens in 30cm distance is at the background rate (representing me standing next to the camera waiting for the "perfect light").

This means that in normal use the lens is not dangerous (because of radioactivity), but you should minimize your handling the lens, especially the glass itself.

[Greg Lockrey]

Whew... ! That was close. :D

[Arne Croell]

To keep things in perspective, the natural radiation at 33000ft is about 2-5µSv/h. So instead of flying from New York to LA you could fondle your Repro-Claron for about 1-2h instead to get the same dose. Also, since the extremities are the least susceptible parts of the body to radiation, normal handling is not really a problem. Just don't carry it in your pants pocket!
A more practical issue is that one should not leave these lenses close to film for a prolonged time, like in a backpack - that could result in fogging. I did some "autoradiographs" of Repro-Clarons on TMAX 100 a few years ago (I just placed the cells on a Readyload envelope), and 19 days gave considerable fog - you can see the result here: http://photo.net/photodb/photo.tcl?photo_id=1221738.

If you like your dosage a little higher, try a 300mm Apo-Lanthar, it comes in at 35µSv/h.

[Greg Lockrey]

Holy crap, Arne! :eek: I'll have to remember to keep it off of my lap.

[Steve Hamley]

Actually the radioactivity of radium daughter is equal to that of the parent in secular equilibrium, which takes about 7 half lives of the daughter, in the case of Ra-228, that's 6.7 x 7 or about 47 years. So if your Th-232 containing Apo-Lanthar (and not all of them did) is 47 years old, there's as much radium as thorium.

http://www.epa.gov/radiation/understand/equilibrium.html

if you're worried, I'll pay the freight to have all those Apo-Lanthars sent to me for safe storage.

Cheers,

Steve

[Michael S. Briggs]

Actually the radioactivity of radium daughter is equal to that of the parent in secular equilibrium, which takes about 7 half lives of the daughter, in the case of Ra-228, that's 6.7 x 7 or about 47 years. So if your Th-232 containing Apo-Lanthar (and not all of them did) is 47 years old, there's as much radium as thorium.

http://www.epa.gov/radiation/understand/equilibrium.html


This process of the daughters growing to their equilibrium concentration is what I was describing in my 04:23 message yesterday. The graph at the URL given by Steve makes it easier to understand -- the graph is the middle one -- "Radionuclide Has a Much Longer Half-Life" for Th-232 having a longer half-life than its first daughter Ra-228. The Table of Isotopes (http://ie.lbl.gov/toi/listnuc.asp?sql=&A1=228&A2=228&Z=88) gives the half life of Ra-228 as 5.75 years. It seems that the use of thorium glass in lenses ended circa 1980--1985. So the newest lens with thorium glass is 23 years / 4 half lives of Ra-228 old. From the graph on the EPA website, 7 half lives is required to reach full equilibrium, but 4 half lives is most of the way there. The other daughters have even shorter half lives (http://en.wikipedia.org/wiki/Decay_chain). So decay chains in the thorium glass of lenses have reached or nearly reached equilibrium all the way down to the final radioactive daughter.

[Greg Lockrey]

Actually the radioactivity of radium daughter is equal to that of the parent in secular equilibrium, which takes about 7 half lives of the daughter, in the case of Ra-228, that's 6.7 x 7 or about 47 years. So if your Th-232 containing Apo-Lanthar (and not all of them did) is 47 years old, there's as much radium as thorium.

http://www.epa.gov/radiation/understand/equilibrium.html

if you're worried, I'll pay the freight to have all those Apo-Lanthars sent to me for safe storage.

Cheers,

Steve

:eek: :eek: Right away, Steve. :D :rolleyes: