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05-26-2016, 03:16 PM - 3 Likes   #1
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Radioactive Lens Measurements

Purpose

There is a lot of talk on the interweb of radioactive lenses, several youtube videos showing highlighting the fact etc. Since I have a small collection of M42 glass and when I found a cheap Geiger counter I decided to go for it. Note that I don't believe that these lenses are dangerous in any way. Measurements are made 5 cm from the lens, with caps of. Even the plastic cap or doubling of the distance will make significantly lower results. The advice would be not to sleep with the rear element of a radioactive lens 5 cm or less from your eye? Anyway, to the fun part!

Method

I have used a simple instrument for measuring radioactivity that is connected to a smartphone or tablet via the headphone jack. The model is called SMART LAB FSG-001 SMART GEIGER COUNTER and specifications of the sensor are measurement of Gamma X-ray radiation with a measurement error of +/- 15 percent. Added to this is interference from the headphone jack, and that would be different in various devices, so comparison should be made with the same device. My setup was the same during all these tests, and also the device was set to “airplane mode” to not allowing any wireless signals to interfere. Between the device was also a 50 cm extension cord to allow more free movement of the sensor. Not to block any lens elements all lenses was tested with the aperture wide open both for front and back measurements. All test where at least tested for 30 minutes to provide some accuracy and being able to compare between the lenses.




Results
  • Super-Multi-Coated TAKUMAR 20mm F4.5 (Rear: 0,81 CPM, Front: 0,28 CPM)
  • Super-Multi-Coated TAKUMAR 24mm F4.5 (Rear: 0,19 CPM, Front: 0,27 CPM)
  • Super-Multi-Coated TAKUMAR 28mm F3.5 (Rear: 0,26 CPM, Front: 0,25 CPM)
  • Super-Takumar 35mm F2 (Rear: 6,71 CPM, Front: 0,23 CPM)
  • Super-Multi-Coated TAKUMAR 35mm F3.5 (Rear: 0,11 CPM, Front: 0,33 CPM)
  • Super-Multi-Coated TAKUMAR 50mm F1.4 (Rear: 19,73 CPM, Front: 1,52 CPM)
  • Super-Multi-Coated MACRO TAKUMAR 50mm F4 (Rear: 0,36 CPM, Front: 0,10 CPM)
  • Super-Multi-Coated TAKUMAR 55mm F1.8 (Rear: 13,24 CPM, Front: 0,62 CPM)
  • Super-Takumar 55mm F1.8 (Rear: 0,25 CPM, Front: 0,12 CPM)
  • Super-Multi-Coated TAKUMAR 135mm F2.5 (Rear: 0,19 CPM, Front: 0,26 CPM)
  • Super-Multi-Coated TAKUMAR 135mm F3.5 (Rear: 0,22 CPM, Front: 0,18 CPM)
  • Super-Multi-Coated TAKUMAR 200mm F4 (Rear: 0,12 CPM, Front: 0,34 CPM)
  • Super-Multi-Coated TAKUMAR 300mm F4 (Rear: 0,16 CPM, Front: 0,24 CPM)

All CPM (Count Per Minute) values larger than one are highlighted yellow. I don't believe that the SMART LAB FSG-001 is an accurate tool for measuring specific values, but since I tested all values for at least 30 min they should be comparable within the results presented here, to say what lenses are more radioactive than other, and in what rough magnitude. What I consider to be radioactive lenses based on these measurements are marked with bold letters. If I get a hold of more old lenses I will add them to the chart! To complete this post why not show a portrait with one of the radioactive lenses

Pentax K-01, Super-Multi-Coated TAKUMAR 50mm F1.4 @ F1.4, 1/320s, ISO100



Last edited by DonThomaso; 05-26-2016 at 03:39 PM.
05-26-2016, 03:29 PM   #2
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Radioactive or not, when these lenses lead to superior results (like demonstrated on your portrait), who cares about some gamma ray? (Anyway after Chernobyl there are worse things around us...)
05-26-2016, 04:26 PM   #3
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Several very early Takumars, especially 50mm FL and especially the f1.4, used rare earth (lanthanum) glass, as did the Voigtlander "APO-lanthar" series of lenses. Back in about the late '60s or early '70s, the radioactive property of the 50mm f1.4 Takumar was demonstrated by leaving one resting atop a sheet of enlarging paper in a darkroom for some time (overnight as I recall), then developing the paper to reveal a circular spot created by the lens. The danger was judged no greater than the luminous radium impregnated dials or hands of wrist watches which I think are no longer in production.
05-26-2016, 04:41 PM   #4
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Yay

I have the 50/1.4. I had to research it a bit after seeing this. The good news is that it is alpha radiation which is stopped by as little as paper. So, a magnesium camera body. . .

And, what a radiant model you used for illustrating picture quality. hehehe

05-26-2016, 05:05 PM - 3 Likes   #5
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Thank you for all your data, Don.

I'll just add in a recent pic of your model:

05-26-2016, 06:30 PM   #6
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Thanks for sharing. I found that quite illuminating...

Companies such as Tracer, or Nite Watches, of England, still use Tritium phials for illumantion. https://www.nitewatches.com/store/us/mx10/show/all/
05-27-2016, 05:04 AM   #7
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Iove my radioactive glass!

Out of curiosity, do you have the opportunity to measure the equivalent K lenses? I mean the K50mm f1.4 and the K55mm f1.8...people say they are not radioactive but my understanding is that they are the same optical elements in a different package.
05-27-2016, 05:16 AM   #8
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QuoteOriginally posted by WPRESTO Quote
Several very early Takumars, especially 50mm FL and especially the f1.4, used rare earth (lanthanum) glass, as did the Voigtlander "APO-lanthar" series of lenses.
Pentax eyepieces for telescopes and spotting scopes (XW and XO series) are still made with lanthanum, according to Pentax's promotional material. I don't know if they're radioactive.

05-27-2016, 05:41 AM   #9
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Original Poster
Thank you all for the appreciation of my little test! I can add more when I have time, I tested all my m42 takumars, but have some newer lenses (that I don't think is radioactive) that I can test, but that is only a handful of K (28/3.5) and M (40/2.8 50/1.4, 50/1.7, 75-150/4) glass.

QuoteOriginally posted by Cuthbert Quote
Iove my radioactive glass!

Out of curiosity, do you have the opportunity to measure the equivalent K lenses? I mean the K50mm f1.4 and the K55mm f1.8...people say they are not radioactive but my understanding is that they are the same optical elements in a different package.
05-27-2016, 06:27 AM   #10
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QuoteOriginally posted by DonThomaso Quote
Thank you all for the appreciation of my little test! I can add more when I have time, I tested all my m42 takumars, but have some newer lenses (that I don't think is radioactive) that I can test, but that is only a handful of K (28/3.5) and M (40/2.8 50/1.4, 50/1.7, 75-150/4) glass.
No the M series have been redesigned, but I strongly suspect the K55mm f1.2 might be radioactive, I left a film inside my KX for six months and when I developed it it had a yellow cast.

Another lens famous for being radioactive is the Canon FD 35mm f2 first version with concave front element, probably even more than the Tak. DR Summicrons also contain Lanthanium, as well as the excellent Industar 61LD.

It appears than more radioactive they are better they take pics!
05-27-2016, 10:37 PM - 1 Like   #11
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I did my own tests some time ago, and be prepared, if you test a lens which appears radioactive, but populair believe is that it is not radioactive, they won't believe you.
Rumours on the internet are more trustworthy than actual measurements.
05-28-2016, 12:16 AM   #12
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QuoteOriginally posted by glasbak Quote
I did my own tests some time ago, and be prepared, if you test a lens which appears radioactive, but populair believe is that it is not radioactive, they won't believe you.
Rumours on the internet are more trustworthy than actual measurements.
Nice work, good idea with the serial numbers, think I'll add those as well since some lenses were produced over a very long time. Now we have two sources then, so the popular opinion might change
05-28-2016, 03:08 AM   #13
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QuoteOriginally posted by glasbak Quote
I did my own tests some time ago, and be prepared, if you test a lens which appears radioactive, but populair believe is that it is not radioactive, they won't believe you.
Rumours on the internet are more trustworthy than actual measurements.
Both of your measurements are extremely interesting, but you use different measurement units so they are not directly comparable, I also thought just the second cemented element in the SMC Tak was radioactive, while you said three elements are.

I am surprised to see that the K55mm f1.8 and f2 are not radioactive, I thought they were carry over from the Takumar era.

Also...can we talk about a "radioactive look"? I noticed that all my Thorium and Lanthanium lenses are excellent performers, not that are many, but for instance I noticed a superior image quality of the K50mm f1.4 in comparison to the smaller M50mm f1.4.

The Canon FD35mm f2 is an excellent performer but when I got it it was so yellowed that it didn't look like a lens with a very warm filter, but it was like shooting colour with a proper yellow filter:



This is how I found the last three exposures of a Portra 160 film that rested in a KX with a K50mm f1.4 for a while:



The other shots display a normal colour balance but they weren't left in front of the lens for long as I "forgot" the camera for quite a long time.


Last edited by Cuthbert; 05-28-2016 at 03:25 AM.
05-29-2016, 03:35 AM   #14
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I DO SEE RADIATION IN THESE SHOTS WHY UR DOING THIS TO ME AHHHH MY EYES WHAT HAV U DONE!!!111ONE

P.S.
DT,
There are different types of radioactivity like alpha-radiation, gamma-radiation and so forth. I'm not sure what that sensor is sensitive to and I'm kinda lazy to lurk around for its specs, just adding 2c to your very intriguing and interesting post. And since your measurement setup is quite sensitive to its own design and layout, it would be very nice should you have added measurements for some well-known nukes like bananas, coal, granite or nuts so we could have the base-line to compare the lens radiation to.

Thanks,
Zig
05-29-2016, 01:26 PM   #15
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QuoteOriginally posted by Siegfried Quote
I DO SEE RADIATION IN THESE SHOTS WHY UR DOING THIS TO ME AHHHH MY EYES WHAT HAV U DONE!!!111ONE

P.S.
DT,
There are different types of radioactivity like alpha-radiation, gamma-radiation and so forth. I'm not sure what that sensor is sensitive to and I'm kinda lazy to lurk around for its specs, just adding 2c to your very intriguing and interesting post. And since your measurement setup is quite sensitive to its own design and layout, it would be very nice should you have added measurements for some well-known nukes like bananas, coal, granite or nuts so we could have the base-line to compare the lens radiation to.

Thanks,
Zig
https://en.wikipedia.org/wiki/Banana_equivalent_dose

0.1 microsievert, this means that according to what Glasbak has reported ingesting a 50/1.4 Takumar is equivalent to eating 650 bananas.
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