Repro Claron Question

[Kevin Crisp]

I have several of the 305mm versions. One of them is quite different from the other two. On the odd one, the rear element is held in by a black collar, holding a a coated round piece of glass, kind of like a UV filter. The piece of glass is just a piece of transparent glass with no correction that I can see. If you unscrew it, the rear element will fall out of the barrel. I am currently UV treating this lens to get the tea stain out. Under a UV light, this flat piece of glass will fluoresce like crazy, a bright glowing disc the color of Mountain Dew.

Anyone know the purpose of this kind of construction? I obtained a factory pamphlet circa 1969 and nothing in there looks like this. I did ask this question a couple years back, I know, but the UV effect is a new factor.

Thanks.

[otto.f]

Perhaps it has to with the radioactivity this Repro Claron lenses are said to contain, at least the 9/210 I have. I wonder though if that can be an issue because there’s a half-life of 9 years I learned from this forum somewhere. And these lenses are from the sixties, no? If I were you I’d throw away that neutral filter.

[Daniel Unkefer]

I just got a nice 305 Repro Claron from the UK, with calibrated professionally Compur shutter beautiful aperture scale also calibrated for my new 165mm barrel Schneider Angulon. Double duty shutter beautiful condition. For my 4x5 Plaubel Profia cameras

I know these were prolly from the Graphic Arts industry prolly Dialyte 45 degree optics perhaps adjusted to work best at average copy-size reproduction ratios. I work forward to investigating the Repro Claron further. Has a very good reputation

Also have the original Repro Claron graphic arts barrel mount engraved correctly and a perfect condition 165 Angulon Schneider barrel

Might work OK on 5x7

[Neal Chaves]

I just obtained a nice 210/9 Repro Claron #9959440 in Synchro Compur. Just mounted it and will be looking at it on the 8X10 camera later today. Glass is crystal clear. I was surprised to read about possible radio activity so I checked it. I've always had a rad meter of some kind around since the 70s. Like everything else, new ones are tiny, inexpensive and loaded with features. MY GQ GMC-500+ averages 19 counts per minute background in my lab, and 26 CPM at the lens. Not too bad.

[Kevin Crisp]

What I am wondering about is why any lens manufacturer would put a clear piece of glass on the back of the lens like this. It clearly is never intended to be removeable, as the rear group falls out if you take it off.

Neal

I think you will find that 210 R Claron isn't going to get close to covering 8X10. It did test it on 5X7 with no movements and it was very sharp edge to edge at infinity. It makes a great 4X5 compact 210.

[Doremus Scudder]

... If I were you I’d throw away that neutral filter.

If the "neutral filter" is original equipment and part of the lens design, and especially if it holds the rear elements in place, I'd recommend you keep it :)

The rear filter element is certainly coated (or it wouldn't fluoresce) and designed to do something important, from color-correction to removing aberrations like color fringing, etc.

Maybe Dan Fromm or one of the other lens gurus here will chime in with their expertise.

Doremus

[Dan Fromm]

Doremus, thanks for the kind word. So you'll know, when I look at myself in the mirror I don't see a guru, I see a silly old man.

I think you're right about the rear element, especially since it hold the rear group in.

[otto.f]

“ especially if it holds the rear elements in place, I'd recommend you keep it ” :) yes!

[Mark Sampson]

I always understood that lenses which used thorium glass had those elements internal to the lens- not least to let the external elements absorb the radiation. The thorium glass-containing lenses that I'm most familiar with, for the Kodak Beacon Precision Enlarger, were designed that way.
Perhaps this mystery element serves the same purpose? Which would not explain why this one is different from other Repro-Clarons.

[Greg]

Under a UV light, this flat piece of glass will fluoresce like crazy, a bright glowing disc the color of Mountain Dew.

In the past I have illuminated many of my lenses with short and long wave UV lights and some glass fluorescing was quite common among 1950s and later optics. To this day I have never read a good explanation of what caused the fluorescence. I always assumed that it was the lens coating and not the glass but could be wrong about that.

[Dan Fromm]

I always understood that lenses which used thorium glass had those elements internal to the lens- not least to let the external elements absorb the radiation. The thorium glass-containing lenses that I'm most familiar with, for the Kodak Beacon Precision Enlarger, were designed that way.
Perhaps this mystery element serves the same purpose? Which would not explain why this one is different from other Repro-Clarons.

I b'lieve that my former 55/8 Repro Claron's outer elements -- remember, these lenses are 4/4 dialyte types -- were the radioactive ones.

[Daniel Unkefer]

What I am wondering about is why any lens manufacturer would put a clear piece of glass on the back of the lens like this. It clearly is never intended to be removeable, as the rear group falls out if you take it off.

Neal

I think you will find that 210 R Claron isn't going to get close to covering 8X10. It did test it on 5X7 with no movements and it was very sharp edge to edge at infinity. It makes a great 4X5 compact 210.

Well you could install gel filters behind the lens and behind the lens is a good place to mount them. Less reflections inside the bellows.

[Neal Chaves]

I had a chance to look through the 210/9 Repro-Claron on the 8X10 in bright sunlight conditions. The center does definitely look hot wide open, extreme fall-off on edges and corners, but image visible all across the frame. Then I closed to f32 and the image looks much more evenly illuminated and sharp out to the corners. This is a lens one would use at f64 on 8X10. I had read favorable reports about these 210/9. That's why I bought this one.

[Dan Fromm]

I had a chance to look through the 210/9 Repro-Claron on the 8X10 in bright sunlight conditions. The center does definitely look hot wide open, extreme fall-off on edges and corners, but image visible all across the frame.
Lens abuse. Schneider claims that the 210/9 RC covers 178 mm at infinity, aperture not specified. 46 degrees, pretty much the norm for process dialytes.

[domaz]

I have several of the 305mm versions. One of them is quite different from the other two. On the odd one, the rear element is held in by a black collar, holding a a coated round piece of glass, kind of like a UV filter. The piece of glass is just a piece of transparent glass with no correction that I can see. If you unscrew it, the rear element will fall out of the barrel. I am currently UV treating this lens to get the tea stain out. Under a UV light, this flat piece of glass will fluoresce like crazy, a bright glowing disc the color of Mountain Dew.

Anyone know the purpose of this kind of construction? I obtained a factory pamphlet circa 1969 and nothing in there looks like this. I did ask this question a couple years back, I know, but the UV effect is a new factor.

Thanks.

This sounds very strange and my Repro Claron is not like this. A piece of glass glowing green under UV light might suggest it contains uranium. Kind of like the Uranium glass that people collect, it doesn't mean it's extremely radioactive just because it glows green though.

[Bernice Loui]

APO process dialytes are designed to produce an image circle about 46 degrees. Repro-Claron is one of them along with APO ronar, APO nikkor, APO artar and others. They will illuminate more than 46 degrees of image circle giving the impression their "coverage" image circle is much larger than 46 degrees except the lens performance is much degraded. Yet, the common belief is to stop down the lens to tiny apertures like f64 and want to believe all is GOOD.

These APO process dialytes are excellent optically in many ways within their designed image circle of 46 degrees typically at f16 to f32, their small size and moderate market cost makes them appealing to pushing them far beyond their designed and specified lens limitations.

This belief and want to have small ~200mm lenses for 8x10 has become a "thing" of wanting a low cost-small size lens that "covers" 8x10 partly driven with the belief 8x10 IS the ultimate sheet film format, simply not true or correct. Then comes the "artistic" justification of doing what "I" want with what ever since it is much about artistic expression.

At f64 (due to diffraction, not escapable by any lens-optics designer or lens-optic), the Repro-Claron might illuminate a 8x10 sheet of film and might be OK for contact printing (f90 is often ok for contact printing), make a 4x or more projection enlargement will reveal image degradation at the edges of the 8x10 film.


Repro-Claron are known for their slightly radioactive Thorium oxide optical glass. This is why they yellow and are slightly radioactive.
There was a time when Thorium oxide optical glass was popular as it offered highly desirable optical qualities. Since that time, much has changed and better optical glass and artificially grown crystals are available with better performance than Thorium oxide optical glass without the radioactivity.

https://camerapedia.fandom.com/wiki/Radioactive_lenses

https://www.arnecroell.com/voigtlaender.pdf


Bernice




I had a chance to look through the 210/9 Repro-Claron on the 8X10 in bright sunlight conditions. The center does definitely look hot wide open, extreme fall-off on edges and corners, but image visible all across the frame. Then I closed to f32 and the image looks much more evenly illuminated and sharp out to the corners. This is a lens one would use at f64 on 8X10. I had read favorable reports about these 210/9. That's why I bought this one.

[Drew Wiley]

Around and around we go. Published image circle and angle of usage for precise apo dot shape replication with process lenses is a far more stringent standard than general photography. For our own purposes, real-world infinity images circles tend to be much larger with a number of these lenses, especially given the fact we often use smaller stops than the printing industry standard of f/22. And I'm speaking with respect to serious enlargements, and not just contact printing.

I am unfamiliar with Repro Clarons; but a 210 G-Claron in no.1 shutter will cover 8x10 film decently with very limited movements. I'd much prefer a 240 GC instead, or something like a 210 Kowa Graphic in a no. 3 shutter as a wide-angle for 8x10. I do sometimes use a tiny little 240 Fuji A or 250 GC for that purpose; and you really need to get up to a 4X enlargement and look very closely to even notice the minor amount of sharpness loss toward the corners, even at f/45. The shortest true process lens I have is a 240 Apo Nikkor, and it would do just fine at smaller stops with movements if I bothered to put it in a no. 3 shutter, which I have no reason to do.

[Kevin Crisp]

Since this post has already jumped the tracks....

If Seth is still adding catalogues to his camera eccentric site, I'm sending him a 1969 original Repro Claron catalogue.

Running the ones I have through his image circle calculator, I get

210 = 178mm image circle. This is considerably short of the 209mm usually specified for 5x7, but I did test mine on 5X7 at infinity and it was (very) sharp at the edges between f:16 and f:22, which was what I was looking for. So Schneider's claims are conservative, as they are on the G Clarons.

305mm = 259 mm image circle. Never tried mine on 8X10. It works great with movements on 5X7.

355mm = 301mm image circle. People have claimed 8X10 coverage, but I cannot test for this. Well short of the usual 330mm rule of thumb though.

420mm = 357mm image circle. Should be an 8X10 lens with room to spare.

They do go longer, I know Jim Galli had a longer one, but I've never actually seen one of those.

[Bernice Loui]

Been there done this with APO process dialytes such as the Repro Claron. This has been the expectation of the kind of optical performance they must meet center to edge.. Be assured APO process dialytes do NOT have this level of optical performance outside of their specified image circle of about 46 degrees. Not just resolution, color rendition, geometric distortion and other lens aberrations non APO process dialytes can not achieve at larger image circles.

https://www.largeformatphotography.info/forum/showthread.php?164451-5x7-Ektachrome-Epson-4990-scanner-vs-Wild-M420-microscope


Will the 210mm Repro Claron "cover" 8x10, very possible. Will the 210mm Repro Claron have the optical performance illustrated in the above post, NO. But that does not mean or imply the greatly reduced optical performance is acceptable for some.. Largest sheet film size that could be OK at infinity for 210mm would be 4x5 Max.


Much about awareness and what is acceptable,
Bernice

[Drew Wiley]

Process lenses sure as heck can perform superbly larger than 46 degrees - maybe not quite up to their center optimum, but certainly better than almost all regular view camera lenses of equivalent focal length I can think of. I prove that to myself over and over and over again with my Apo Nikkor dialytes. But would I use a 210 for 8x10 format? No way, not unless it was a contact print. Again, I know nothing about Repro Clarons per se. G-Clarons I do.

[Mark Sampson]

It's worth noting that the Repro-Claron was Schneider's answer to the Goerz Red Dot Artar; both are 4-element air-spaced symmetrical designs.
When Schneider bought the Goerz American Optical Co. in the early '70s, they discontinued the R-C and kept the Artar in the lineup (until at least the mid-1990s).
While making and marketing the entirely different design G-Claron at the same time. In their ads Schneider said the the Apo-Artar was the best lens for photographing jewelry... I suppose by then the graphic-arts camera market (for which these lenses were meant) was in terminal decline.

[Kevin Crisp]

My entirely subjective standard for lens performance is looking at the negative with a powerful magnifying glass. If the image's fine details are very sharp, looking like an etching, then it passes. The 210 repro claron passed at the corners easily when I tested it on 5x7 film at infinity. I think the 210 R Claron is a fine very small lens that is very capable for 4x5, with room for as much movement as I normally use. The G Claron does indeed have much more coverage. I have used the 305 R Claron on 5x7, with at least an inch of rise and it was very sharp edge to edge, corner to corner.

[Drew Wiley]

G-Clarons have just as much real-world image circle as general-purpose 70-degree plasmats, with even better resolution toward the nether regions of the circle than most. Likewise, Fuji A-series "Super Plasmat" lenses. But Fuji was smart enough to point out that feature to regular photographers in their brochures, rather than just issue a set of specs based on earlier repo lens conventions like Schneider did.