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12-16-2016, 03:33 PM   #1
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How Hot is Super-Takumar 35mm F2 (late, 49mm version): Tested

So my Super-Takumar 35mm F2 has served me well and has some sentimental values to me. However out of curiosity I bought a Geiger Meter to see how hot the glass in my copy (S/N 39050xx, catalog code 43931).

The meter I used: Smart Geiger Nuclear Radiation Gamma X-ray Personal Detector Counter Tester Sensor for Smartphone Amazon.com: Smart Geiger Nuclear Radiation Gamma X-ray Personal Detector Counter Tester Sensor for Smartphone Apple iPhone 4 4s 5 5s 6 iPad, Android Phone Samsung Galaxy S3 S4 S5 S6 Note 3 Lg G G2 G3 G App: Cell Phones & Accessories coupled with a Amazon Fire HD 8 2016.

Readings

Surface of rear element, uncapped:


Surface of rear lens cap (Tamron Adaptall-2 M42 cap, slightly taller than usual caps):


Side of lens, aperture ring:


Surface of front element, uncapped:


Surface of front lens cap (Sensei 49mm center-pinch type):


Comments and thoughts are welcome.

12-16-2016, 03:55 PM   #2
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How about measurements from the back of the camera and from the viewfinder with the lens mounted?

Let's see the International Commission on Radiological Protection (ICRP) annual limits to the skin or extremities:
- A shallow-dose equivalent of 50 rems (0.50 Sv) to the skin or to any extremity.

So 0.50 Sv = 500000 microSv

Given a measurement of 40 microSV per hour you would need to be exposed 520.8333 days @ 24 hours per day to receive a total dosage of 0.50 Sv.

Last edited by Not a Number; 12-16-2016 at 04:07 PM.
12-16-2016, 04:30 PM - 1 Like   #3
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"exposed" meaning you'd need to have the lens taped to your forehead for more than 17 months.
12-16-2016, 05:25 PM   #4
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QuoteOriginally posted by Not a Number Quote
How about measurements from the back of the camera and from the viewfinder with the lens mounted?

Let's see the International Commission on Radiological Protection (ICRP) annual limits to the skin or extremities:
- A shallow-dose equivalent of 50 rems (0.50 Sv) to the skin or to any extremity.

So 0.50 Sv = 500000 microSv

Given a measurement of 40 microSV per hour you would need to be exposed 520.8333 days @ 24 hours per day to receive a total dosage of 0.50 Sv.
I have misplaced my M42-PK ring so I can't test it on my K-S2 now.

This is the reading taken from the EVF of an NEX-6 mounted with this lens and Mitakon Lens Turbo II (which claims to have used lanthanum glass), as this is my usual configuration for this lens now.



12-16-2016, 05:33 PM   #5
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QuoteOriginally posted by butangmucat Quote
Amazon Fire HD 8 2016
Looking up the specs for the Amazon Fire HD - there aren't any dedicated radioactivity detectors on the device, which makes the readings you have posted here rather questionable.
12-16-2016, 05:42 PM   #6
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QuoteOriginally posted by Digitalis Quote
Looking up the specs for the Amazon Fire HD - there aren't any dedicated radioactivity detectors on the device, which makes the readings you have posted here rather questionable.
The device is designed to plug into the mic jack and data is gathered by an Android app. I did follow the instructions to enable flight mode during the measurements.

I am not trying to claim these figures are reliable, but they should be in an acceptable range if the device is not flawed. I did post the devices I use as a reference so that others can judge the accuracy of these figures.
12-16-2016, 10:20 PM   #7
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QuoteOriginally posted by butangmucat Quote
The device is designed to plug into the mic jack and data is gathered by an Android app.
I wouldn't trust such at thing in a Belorussian market.

QuoteOriginally posted by butangmucat Quote
they should be in an acceptable range if the device is not flawed. I did post the devices I use as a reference so that others can judge the accuracy of these figures.
There is no way of calibrating the unit, that is my problem. The background radiation of the area you are in could be interfering with the readings.
12-16-2016, 11:33 PM   #8
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QuoteOriginally posted by Digitalis Quote
I wouldn't trust such at thing in a Belorussian market.



There is no way of calibrating the unit, that is my problem. The background radiation of the area you are in could be interfering with the readings.

Couldn't you take a reading in a room, with the lens out of the room, to get a background radiation level, then bring the lens in that room and test it?

12-17-2016, 02:21 AM   #9
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Without some sort of standard to measure and calibrate certainly the readings are suspect. However if the app does what it is supposed to do (measure ionizing radiation) at least we can see what the relative attenuation or shielding effects of the lens caps, lens and camera body and distance are.
12-17-2016, 03:23 AM - 1 Like   #10
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I've been shooting with Takumars almost exclusively for many years now, including the "hot" ones, and I'm not planning to stop. Everything I've ever read on the subject indicates that any threat from thoriated lenses is pretty much insignificant.

And anyway, I live on Dartmoor, which is basically a 365 square mile lump of radioactive granite. Government figures indicate that I get a dose of more than 30 millisieverts, so my Taks are really the least of my worries.

Annoyingly, after absorbing so much radiation for so long, I still haven't developed any mutant superpowers. I'm starting to wonder if all those comic books I read as a kid weren't scientifically accurate after all.
12-17-2016, 03:51 AM   #11
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QuoteOriginally posted by butangmucat Quote
The meter I used: Smart Geiger Nuclear Radiation Gamma X-ray Personal Detector Counter Tester Sensor for Smartphone
This is a fail in start because this meter detects gamma and x-ray only. no beta or alpha. And thorium is almost exclusively alpha emmiter with a half-life of some 14 billion years. Gamma and x-ray that you have detected came from radon which then decayed to something else that emits these weak gammas.

While super takumars are hot, they are not hot enough. Thorium oxide posed a greater threat to people who worked with it in plants but to us "end consumers" it poses no threat since it is in glass, but even if you shatter it, nothing much would happen. You might get some problems if you put that rear element 1cm from your eye and keep it like that 24/7 for a year, without blinking. I talked to a guy that works in nuclear research lab in my country and his explanation was very simple. Think of that rear element as weak earbuds playing some music. When you are 1meter from them, you hardly hear them, but you hear them when you put them in your ears, and even then they are not so loud.
I was very paranoid about that radiation when i bought my 50mm 1.4, but I learned that it is nothing special. There are far more common situations in life that could pose a greater radiation threat than thoriated lens.
12-17-2016, 04:14 AM   #12
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QuoteOriginally posted by butangmucat Quote
This is the reading taken from the EVF of an NEX-6 mounted with this lens
Dude, not trying to be snarky, but... wtf? It's an electronic viewfinder...
12-17-2016, 06:31 AM   #13
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QuoteOriginally posted by Digitalis Quote
I wouldn't trust such at thing in a Belorussian market.



There is no way of calibrating the unit, that is my problem. The background radiation of the area you are in could be interfering with the readings.
QuoteOriginally posted by Not a Number Quote
Without some sort of standard to measure and calibrate certainly the readings are suspect. However if the app does what it is supposed to do (measure ionizing radiation) at least we can see what the relative attenuation or shielding effects of the lens caps, lens and camera body and distance are.
The app has a built-in calibration function, which calibrates the meter when first plugged in or can be invoked manually.
12-17-2016, 08:14 AM - 1 Like   #14
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If I keep using these I might die of cancer in 2075.

Ruh Roh.
12-17-2016, 02:48 PM   #15
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QuoteOriginally posted by butangmucat Quote
he app has a built-in calibration function, which calibrates the meter when first plugged in or can be invoked manually.
And what radioisotope are you calibrating it with? the standard material for calibration is Caesium-137 for medical applications.

If the device is calibrating itself with background radiation - it won't be very accurate at all because of the highly variable nature of background radiation.
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