Is there any M-mount radioactive Summicron 50/2 ?

[Ambrose]

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Hi everyone.

I found a radioactive 50/2 but it’s M mount,

I’m wondering if this is very rare or it has been modified?

Sr: 1096120

thanks for your answer 

[jaapv]

First check whether it is really M-mount and not a stuck adapter.

[a.noctilux]

3 hours ago, Ambrose said:

Hi everyone.

I found a radioactive 50/2 but it’s M mount,

I’m wondering if this is very rare or it has been modified?

Sr: 1096120

thanks for your answer 

Interesting,

can you load some pics of the mount ?

Are the lenses yellow ?

Edited January 5, 2020 by a.noctilux

[sabears]

4 hours ago, Ambrose said:

Hi everyone.

I found a radioactive 50/2 but it’s M mount,

I’m wondering if this is very rare or it has been modified?

Sr: 1096120

thanks for your answer 

What's the reason you think it's radioactive?

[luigi bertolotti]

The real oddity of your Summicron is the M Mount, which officially started with later numbers (even if Lager displays a M Mount 1.042.553) ; the question of "radioactivity" is rather subtle… according to some authors, even when the change of glass ("Thorium free")  became effective, some lenses can show the typical yellowish hue (and a "slight" radioactivity) due to residual contamination of Thorium into the melting pots used to produce the glass elements…

Pictures of your lens, with details of the flange, are welcome !

 

Edited January 5, 2020 by luigi bertolotti

[frame-it]

interesting reading

https://www.orau.org/ptp/collection/consumer products/cameralens.htm

[Ambrose]

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5 hours ago, luigi bertolotti said:

The real oddity of your Summicron is the M Mount, which officially started with later numbers (even if Lager displays a M Mount 1.042.553) ; the question of "radioactivity" is rather subtle… according to some authors, even when the change of glass ("Thorium free")  became effective, some lenses can show the typical yellowish hue (and a "slight" radioactivity) due to residual contamination of Thorium into the melting pots used to produce the glass elements…

Pictures of your lens, with details of the flange, are welcome !

 

 

9 hours ago, a.noctilux said:

Interesting,

can you load some pics of the mount ?

Are the lenses yellow ?

Thanks for your answer, please check these photos.

Welcome, dear visitor! As registered member you'd see an image here…

Simply register for free here – We are always happy to welcome new members!

[jaapv]

9 hours ago, frame-it said:

interesting reading

https://www.orau.org/ptp/collection/consumer products/cameralens.htm

The dose concerns in that article are funny: the max. dose in most countries is 100 mRem = 1 mSv per year for the general public, 20 times that value for professional users. I think the author is confusing Rem-s (obsolete) with Sieverts-s. 1 Sv = 100 Rem.

[kinch123]

Am I correct in inferring from the questions above that it is expected that the screw mount versions of this lens have the radioactive element(s) and M-Mount versions do not?

A bit curious as I picked up an M-Mount version several years back and have made a special point of not ingesting it or sleeping on top of it.

 

[jaapv]

The mount, from the image, might well be an adapter. Could we have a more clear view? 

[luigi bertolotti]

1 hour ago, jaapv said:

The mount, from the image, might well be an adapter. Could we have a more clear view? 

Image is indeed not too clear… but in the 2nd pic the mount with DOF scale looks to me slanted and with the small red painted dot, as must be in an original BM item.. (the plastic red dot arrived later)

 Front writing consistent with the one of my SM 1.043.355 (writings with different orientation : my older 920.382 hasn't "GmbH" and the writings have the same orientation)

Fine Yellow color in front lens… but of course, can't say anything about radioactivity…

Edited January 6, 2020 by luigi bertolotti

[luigi bertolotti]

3 hours ago, kinch123 said:

Am I correct in inferring from the questions above that it is expected that the screw mount versions of this lens have the radioactive element(s) and M-Mount versions do not?

 

 

Generally speaking, the M-Mount version ought to be not radioactive for the simple reason that it was introduced in 1954 with M3, while the new LaK9 glass, no thorium-oxide - not radioactive, was officially introduced in standard production in 1952 (good story here  : http://www.marcocavina.com/articoli_fotografici/50mm_Leica_a_telemetro/00_pag.htm ) On the contrary, many screw Mount items were built before 1952 so that several are radioactive (not all, of course… thousands were built after 1954) 

But wide margins of uncertainess do exist, considering that Summicron was a lens made in thousands, at high rates, and the basic optical cell (assembled glass elements) was an important sub-assembly probably manufactured in a proper  department, and is maybe the same for SM and BM versions.

 

Edited January 6, 2020 by luigi bertolotti

[frame-it]

i though it was usually a brownish deep yellow color?

[jaapv]

Even after the Thorium addition was discontinued and replaced by other glass, the product was still "radioactive" for a few batches. The cause was that the glass smelting furnaces were contaminated by Thorium. So early non-Thorium lenses can exhibit brown/yellow discolouration through radio-activity.

Additionally, optical glass was -and is- produced in batches, so some glass elements used in 1954 may well have come from an earlier production run.

 

2 hours ago, luigi bertolotti said:

But wide margins of uncertainess do exist,

 

[Ambrose]

2 hours ago, jaapv said:

Even after the Thorium addition was discontinued and replaced by other glass, the product was still "radioactive" for a few batches. The cause was that the glass smelting furnaces were contaminated by Thorium. So early non-Thorium lenses can exhibit brown/yellow discolouration through radio-activity.

Additionally, optical glass was -and is- produced in batches, so glass elements used in 1954 may well have come from an earlier production run.

 

2 hours ago, luigi bertolotti said:

Generally speaking, the M-Mount version ought to be not radioactive for the simple reason that it was introduced in 1954 with M3, while the new LaK9 glass, no thorium-oxide - not radioactive, was officially introduced in standard production in 1952 (good story here  : http://www.marcocavina.com/articoli_fotografici/50mm_Leica_a_telemetro/00_pag.htm ) On the contrary, many screw Mount items were built before 1952 so that several are radioactive (not all, of course… thousands were built after 1954) 

But wide margins of uncertainess do exist, considering that Summicron was a lens made in thousands, at high rates, and the basic optical cell (assembled glass elements) was an important sub-assembly probably manufactured in a proper  department, and is maybe the same for SM and BM versions.

 

Sorry for the poor quality, having trouble with upload.

i upload the photos to dropbox

https://www.dropbox.com/sh/ktnuloskmxzcd8c/AADTWjpu_lEZMSAPApNZaj7pa?dl=0

And this Lens was found at Germany 

[luigi bertolotti]

Thanks Ambrose : M mount original, no doubt, and with a "abnormally low" serial number (for a BM), which - radioactive or not - makes it an uncommon item.

 

[a.noctilux]

Ambrose,

I've seen the pictures of this lens better in dropbox.

I think now no doubt this is in M mount.

The number  "7" in the "groove" means real measured 51.6mm optical cell.

How do you know it is radioactive ?

 

The rear lens element on your lens has different coating than mine which is radioactive screw mount of 1951.

[Ambrose]

23 minutes ago, luigi bertolotti said:

Thanks Ambrose : M mount original, no doubt, and with a "abnormally low" serial number (for a BM), which - radioactive or not - makes it an uncommon item.

 

Thank you Bertolotti, this question budder me for a long time. about why i know this is a radioactive because i have a geiger counter.

[Ambrose]

 

22 minutes ago, a.noctilux said:

Ambrose,

I've seen the pictures of this lens better in dropbox.

I think now no doubt this is in M mount.

The number  "7" in the "groove" means real measured 51.6mm optical cell.

How do you know it is radioactive ?

 

The rear lens element on your lens has different coating than mine which is radioactive screw mount of 1951.

Thank you for telling me about the number7 `s meaning , about the radioactive , i use my geiger counter to check the lens.

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[kinch123]

11 hours ago, luigi bertolotti said:

Generally speaking, the M-Mount version ought to be not radioactive for the simple reason that it was introduced in 1954 with M3, while the new LaK9 glass, no thorium-oxide - not radioactive, was officially introduced in standard production in 1952 (good story here  : http://www.marcocavina.com/articoli_fotografici/50mm_Leica_a_telemetro/00_pag.htm ) On the contrary, many screw Mount items were built before 1952 so that several are radioactive (not all, of course… thousands were built after 1954) 

But wide margins of uncertainess do exist, considering that Summicron was a lens made in thousands, at high rates, and the basic optical cell (assembled glass elements) was an important sub-assembly probably manufactured in a proper  department, and is maybe the same for SM and BM versions.

 

Thank you Luigi. Just checked the serial number which is 1166722 --> 1953 production. Cannot see any visible discolouration of elements. However could well be affected by the smelter contamination Jaapv mentions + there are, as you say, no absolute certainties given batch nature of production. Out of curiosity I should run it by a Geiger Counter one day.