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Radioactive Leica 50mm f2 Collapsible Summicron (M39) good idea as only Lens?

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I am a bit lost with what i have read about the radioactive summis. 

What is the deal with them? Are they more trouble than they are worth because of the browning? How about resale? Do people avoid them?

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Are you sure this is a radio active one? They are pretty rare.

As long as you do not carry them in your pocket all day, every day you should be fine, I suppose.

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according to the seller it is. He was a collector.

 

The concern isn't the radioactivity (which is apparently negligible) but rather the effect of the browning of the lens element I...

Some have said it changes exposure, others that it is a fantastic lens, more others that its good for B&W etc.

Anyone used/own one and know the low down? lol

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I have one (920.xxx) : the simple low down is that is an old Summicron... to say, like an Elmar Red Scale (color and contrast, on a digital M, is identical) with almost 2 stops more, which are completely usable... but not up to what can be achieved, for instance, with my DR Summicron. Probably, my one has been re-polished... fact is that exposure is like it must be.

Edited by luigi bertolotti

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According to the Cavina/Ghisetti excellent book on Summicron, the Chance Brothers radioactive glass was used only in the "pre-production" series with serial numbers up to 922072. Then production changed to the LaK9 Crown (Kron - from which the Summikron was originally named) which is not radioactive.

I believe some of the early coatings can look Amber colored, which can be mistaken for the earlier glass.

I don't have a radioactive Summicron, but do have a few Takumar radioactive lenses that had yellowed badly. I exposed them to a UV (black) light for a day, and they became quite clear; so the color can be removed without harm.

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The difficulty with this lens is to find one without cleaning marks. Because the front glass is soft as chalk, one cleaning swipe with a cloth can be enough to ruin it. And I think that even repolishing and coating will not fix that.


 


 I happen to have one in pristine condition, with only minor faults caused by a starting pitting corrosion that were stopped when Will van Manen gave it a CLA.


 


It certainly is a bit less sharp in the corners compared to the rigid Summicron or DR, but certainly on the cropped M8, differences are very small. The first two stops are excellent and completely in line with the typical Summicron qualities. So even on the M9, I would not hesitate to use it wide open. I think that if this lens would have had a front glass elment as hard as that of the 35 Summilux, its reputation would have been much better.


 


Now, it seems like many collectors have a sample that is not performing up to specs, so it is not  in high regard as much as the later Summicron 50 series.


All I can say is that to my eyes I would prefer this one (in perfect functional condition) to the Summicron III, not for its sharpness, but for its overall rendering qualities.


 


And, these qualities combined with being the smallest (collapsed) and lightest Summicron 50, make it one of my favourite Summicrons.


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I have 1022691, and it registered as 'hot' when tested with a Geiger counter.



 

 

Edited by roydonian

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The radioactivity is caused by the use of thorium/lanthanum in the early 1950s to improve the characteristics of faster lenses. For all practical purposes you get more radioactivity from wearing a watch or even just daily exposure to the elements....but some people freak out at the word "radioactivity". The discoloration typically is caused by, I am told, the effect of the radioactivity on the cement used to join the elements. Anyway some people like the discoloration, as in the case of B&W, they say it acts like a yellow/orange filter. I have a Super Takumar which had this affliction (not heavy, but definitely noticeable). I wrapped the outside of the lens and the outside of, alternatively, the front and rear element with aluminum foil, rubberbanded the lens to a flat on a tripod, and aimed it at the sun for about 8 hrs/day for about 3 weeks. The foil around the edges was so the lens itself didn't get too warm, and the foil across the element was to reflect light back thru the elements after it entered the end pointed at the sun. The end result was a crystal clear lens with higher contrast than when I started. It has been about 5 years now any everything still looks great. The process is not a big deal IMHO, but the results are quite rewarding.

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A "radioactive" Summicron 50mm is first and foremost a collector's item, since its optical performance does not differ from later, non-radioactive Summicrons (I am talking about the collapsible version here, as the later rigid version Summicrons never used radioative glass). The main difference between the collapsible Summicron and its successor, the first rigid Summicron, is performance at full aperture, which is distinctly better with the rigid. From f2.8 or 4 onwards, their performance is indistinguishable, which is why for most situations the collapsible Summicron is still a very good lens even today.

 

Andy

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If you want access to some high intensity light, two sources for this: Firstly your friendly local dentist will have a high intensity source for setting UV hardening epoxy fillings: Secondly a physiotherapist may have a high tensity UVB-C laser, to promote healing of ulcers. The latter would be dependant on the physio's speciality and whether they offer phototherapy. Neither my wife nor my daughter have such a light, as they use an ultrasound instead. 

 

If you are looking for an LTM user, you could do worse than a Canon 5cm/f1.8 "Hiroshi" lens. Its performance is on about a par with the rigid 50 Summicron and they don't seem to go yellow. They are chrome finish with an infinity lock/focus tab. The front element and coating is far more robust than Leica glass of that period. I bought a near mint version last year for $199 from Japan, to use on my Leotax K. They are a bit "shinier" in appearance, than the silky chrome finish Summicrons. The rear two elements can suffer non-cleanable fogging, so check before you buy or get a return agreement. 

 

Wilson

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It's a great lens but as with most of these it suffers from slight browning.

 

I have one that I use on my Barnack LTM's and often via an adaptor on my Monochrom. Unless pixel peeping I can't see any difference between it and my other Leica 50mm lenses. The browning is a bit of an advantage as it gives a slight yellow filter effect!

 

Exposure wise on the Monochrom with through the lens metering there's obviously no bother but on the LTM's I find that I give about 1/2 stop more exposure and that works fine.

 

I'll have a look through my archives and post an LTM film shot and a Monochrom shot made with this lens.

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Pictures from my current project documenting the industrial history of my hometown of Bradford, West Yorkshire, UK.

 

Pic 1 is the 50mm Collapsible Summicron on a Leica 111A on Kentmere 100 film.

 

Pic 2 is the same lens on a Monochrom Mk1.

 

Hope this gives you an idea of how this lens performs - Regards Paul Mac

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I would not recommend an early Thorium glass type 1 Summicron as your only lens. If you want just one classic screw lens then a 50mm f3.5 Elmar, redscale if possible, would be the one. 

 

I had a Thorium Summicron a couple of years ago. The serial number started 920*** which I understand put it in the first batch of 1000. It was OK but not outstanding. I sold it about a year ago for more than three times what it had cost me, to help pay for a nice screw thread 21mm f4 Super-Angulon.

 

These are two pictures taken with the Thorium Summicron. The lighthouse base/white gate picture was taken on a 3g body and the sepia toned light railway picture taken using a Canon 3 body, both on Ilford Delta 100 in Rodinal. Both scanned from A4 darkroom prints.

 

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In my experience it's a very good lens and I'll leave it at that as the OP doesn't seem interested so why should I be!

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Been using a thorium 'cron for 45 years. The glass did go tobacco brown - BUT I rread somewhere on an American site that The IKEA Jansjo worklight gave enough UV of the right sort of frequency to bleach it out in a few days. I had an old ex. RAF UV aircraft instrument lamp so I powered it up and in three days it had nearly cleared the staining. Then the filament popped.

Ser. no 1104466just had it cla'd;. Bootiful. Radiation level about 4kBq. but more than a few inches away it is all gamma. Bigest worry should be emulsion fogging. It is amazing how many lenses used thorium or lanthanum (glass turns orange) dosed glass. The mix, up to 60% by mass of thorium, gives a glass of low internal dispersion and a relatively high refractive index. Good for reducing chromatic aberration.

Keep on clicking

D.Lox

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My Collapsible Summicrons (123xxxx & 125xxxxx) test clean, but several of my Japanese lenses of the 1960s are active, such as Asahi Takumar 55 1.8 & 50 1.4, and Mamiya Sekor 55 1.4 (the most active I have). They don't show much from the front direction, but are strongest from the rear element side. The first Leitz Summicron design used a lead-glass last element to somewhat shield the emulsion.

Some of the Takumar activity must be Gamma emission, as it even shows through the hinged camera back behind the film.

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My Collapsible Summicrons (123xxxx & 125xxxxx) test clean, but several of my Japanese lenses of the 1960s are active, such as Asahi Takumar 55 1.8 & 50 1.4, and Mamiya Sekor 55 1.4 (the most active I have). They don't show much from the front direction, but are strongest from the rear element side. The first Leitz Summicron design used a lead-glass last element to somewhat shield the emulsion.

Some of the Takumar activity must be Gamma emission, as it even shows through the hinged camera back behind the film.

Luckily, as an interventional cardiologist, I always have some lead eyeglasses available

 

The human lens is quite sensitive to radiation damage, with increased risk for cataract due to reduced biological repair activity in lens tissue.

 

Biological harm depends very much on exposure duration, dose rate and minutiae of radiation type and wavelength. For a pro photog of old it may have been a valid risk. For a collector who occasionally takes pictures with a radioactive lens, it most propably will be below the background noise of ordinary natural and civilizatory radiation exposure on an anual level of analysis.

Edited by schattenundlicht

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I am resurrecting this thread to ask about the serial numbers for the radioactive lenses- above TomB said the radioactive lenses go up to serial number 922072 but then two posters after that mentioned having 'hot' summicrons with numbers over 1,000,000?

 

Just now I saw one that sold on ebay as a thorium lens- with < #1095853

 

Is there any consensus on the numbering? Were all lenses radioactive up to a point- or just some? Can you be certain by serial number?

 

 

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