Radioactivity of old manual lenses

[no-X]

I prepared a test of radioactivity on majority of my lenses. Here is the result:

I made measurement for both rear and front elements (1cm distance, if possible). Some results are as expected, but some of them are a bit surprising for me:

S-M-C Macro Takumar 50/4: radioactive... VERY low intensity, but present. I think it uses lanthanum glass.

Super Takumar 35/2.0 V1 / PRO (the big one)... low radioactivity, half than on the later version, which is known to be thoriated... this level of radioactivity could mean utilization of lanthanum glass or very low amount of thorium

S-M-C Takumar 85/1.8: I have never seen this lens in any list of radioactive lenses, but its radioactivity is really evident. It's very untypical, that front side radiates more than the rear one, so the thoriated(?) element is located in front optical group...

Carl Zeiss Jena Biometar 80/2.8 (zebra, P6): next surprise... while the old M42 (alu) version isn't radioactive, the newer one (for medium format cameras) is. Radioactivity level is really low. It could be lanthanum glass or very low amount of thorium...

I made some colored highlights to allow easier orientation... blue = low radioactivity, red = high radioactivity


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[PaulC]

Hey, cool! I might have a hot lens for my P6.

PS: The stability of your background radiation measurements is very impressive and certainly leaves little room for doubt about the accuracy of your results.
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[aleksanderpolo]

Thank you so much, yeah, my S-M-C Tak is first runnerup!

Joking aside, do you have experience of how long it takes to "de-yellow" the lens with UV treatment? I have been putting it behind a window glass under the sun for more than two weeks now.
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Panny GF1

Looking for: More articles to read
Current lens:
m4/3: 20/1.7; 14-45/3.5-5.6
C/Y: CZ 28/2.8; CZ 35/2.8; CZ 50/1.4
G: 45/2; 90/2.8
M: CV 35/1.4
Rollei: 50/1.8
m42: S-M-C Tak 50/1.4, Helios 44-2
F: AI 28/2; AIS 35/2; AIS 50/1.4; E 50/1.8
FL: 55/1.2
FD: Vivitar(Komine CF) 28/2; Kiron 28/2; nFD 50/1.4; nFD 35-105/3.5-4.5
AR: 40/1.8; 50/1.4; Adaptall 35-80/2.8-3.5
MD: Vivitar(Kiron) 24/2; MD 50/1.4
OM: 21/3.5; 24/2.8; 50/1.4; 135/3.5

[no-X]

PaulC: I must say, that the results aren't 100% exact (cheap dosimeter, I have no idea, what aspects can impact the measurement etc., accuracy is at best 20nSv/h - very likely lower), but I think, that all colored results really stands for radioactive glass.

I also found informatio, that both thorium and lanthanum glasses were developed in time and it became so pure, that its radioactivity was almost non-existant. It means, that even non-radioactive lenses can be equipped by thorium/lanthanum elemens.

aleksanderpolo: As I remember, I used 11W UV tube and it took about 5 weeks for S-M-C 50/1.4...
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[Orio]

thanks, very interesting !

It looks like all lenses, regardless of brand and model, have radioactivity levels higher than the background.

I wonder where does it come from - the glass? the coating? the barrel?

Another thing I'd be curious to see, is some test on today's autofocus lenses, to compare.

Which brand and model of detector did you use?
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Orio, Administrator
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[Orio]

Another thing to consider:

if a normal "clean" lens averages around 180 radioactivity, a bag with 6 lenses (not that uncommon, considering that many of these old lenses are small) becomes a not so reassuring 1080 radioatcivity bag that you may carry all day near your abdomen or your lungs (depending on the type of bag).

Something to think about.

It also means that Carsten with his typical trekking setup of 15 or so lenses goes around with a little nuclear bomb hanging from his shoulders!

-
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[no-X]

In fact some lenses slightly lowered the background radioactivity - mainly CCCP models (thick metal parts?).

I used the cheapest one I could get - Radex RD1503.
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[PaulC]

Ooops! Didn't read the chart properly

If we're going to go further we need to determine what kind of radiation you are getting before we start worrying about the cumulative lensing effects of it in Carsten's bag.
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[peterqd]

[Orio]

No-X have you tried to measure your lens cabinet (assuming that you keep your lenses together in one place) at about say 1 mt distance - which would be the typical walking distance ?
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[lwsy711]

Jiri,
Nice job!
Just want to know what is the distance you put your dosimeter away from the lens.
Thanks,
Wei
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Camera: pentax k7, Olympus E-p1
MF lens:
M42: CZJ 20/4, 35/2.4, 50/1.8, 135/3.5, Super Takumar 35/3.5, Yashinon macro 60/2.8, CZ tessar 80/2.8(Exakta to M42), Vivitar 200/3.5
Pk: Cosinon 55/1,2
Exakta: CZJ biotar 75/1.5, Meyer 100/2.8, Meritar 50/2.9
Praktina: CZJ biotar 75/1.5, Primagon 35/4.5
Praktica: CZJ pancolar 80/1.8

[Orio]

[lwsy711]

[Orio]

[Sevo]