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Radioactivity of old manual lenses
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PostPosted: Fri Feb 26, 2010 10:31 pm    Post subject: Reply with quote
no-X wrote:

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.


Not thorium - this is radioactive by itself. However, the non-alpha activity of pure thorium only builds up slowly as the amount of beta- or gamma-radioactive decay products increases - a fresh inner lens made with refined thorium might escape detection.


PostPosted: Fri Feb 26, 2010 10:38 pm    Post subject: Reply with quote
Orio wrote:
peterqd wrote:
I keep my Tak 1.4/50 in a clear plastic box meant for the Mir-1V with no cap, and even though it only gets a little light, it keeps it nice and clear.


Well, Peter, from the data it looks like you should keep the SMC Tak 1.4/50 away from where you seat or sleep, and preferably in a thick metal box if you have one.

Are you being serious or tongue-in-cheek? Smile

That's the reason I asked if we could relate the figures to something I can understand. As just bare numbers they mean very little to me - I just can't tell whether the Tak 50 is dangerous or not, but my instinct tells me that you're over-reacting.

If they were at all dangerous I can't believe, with all our consumer protection and safety laws, that nobody has bothered to issue a safety warning about radioactive lenses or call them all in for destruction. I can't find any cases of anyone being affected by using them in the past, do you know of any?


PostPosted: Fri Feb 26, 2010 10:45 pm    Post subject: Reply with quote
Send me guys all dangerous lenses I will sleep with them LOL.


PostPosted: Fri Feb 26, 2010 10:45 pm    Post subject: Reply with quote
peterqd wrote:

Are you being serious or tongue-in-cheek? Smile


I'm serious because I know that us lens lovers tend to spend a lot of time near our jewels - we don't only use them when we go out to photograph, we handle them, clean them, like to have them near - sometimes when I like to relax without sleeping I take a couple of my lenses and look at them, I like to feel them in my hands - stupid I know Rolling Eyes But to do it with a lens that is 10 times higher than background RA might not be safe.

Quote:
That's the reason I asked if we could relate the figures to something I can understand. As just bare numbers they mean very little to me - I just can't tell whether the Tak 50 is dangerous or not, but my instinct tells me that you're over-reacting.


Peter, think about it, Nox gave us the comparison term, it's the background radioactivity level. It surely depends on the area where you live but I thin kwe can assume that on average, the values of where you live should be similar.
Nox lists background level at about 200. The SMC Tak 1.4/50 is almost 2000 which means 10 times more the background level.
I would not feel safe to have around all the time something that is 10 times more radioactive than normal.
To use it for a photo session is one thing, to have it near where you seat or sleep is something different.

POST SCRIPTUM: exactly today, an Italian tribunal has decided to assign a refund to a person who worked for a company and was forced to use for his job, a cell phone or a cordless phone, continuously, 4-5 hours per day. The person developed a cancer at his inner ear. The tribunal acknowledged that the cell phone continuous use was the cause.


PostPosted: Fri Feb 26, 2010 11:01 pm    Post subject: Reply with quote
There have been warnings regarding radioactive eyepieces on telescopes and rifle sights. Photographic lenses are harmless in use - for optical reasons, the thoriated element is never the front lens, so that the radioactivity (alpha, which does nor even reach far in air) is well contained. Scrapping them could prove expensive, though, and they aren't made anymore, as workplace safety regulations would be close to those in a nuclear plant.


PostPosted: Fri Feb 26, 2010 11:09 pm    Post subject: Reply with quote
Sevo: Thanks

other data:

1m distance from my lens cabinet (closer to the place where are 35+50mm lenses): 200 nSv/h

similar measurement in another room: 170 nSv/h


S-M-C Takumar 50/1.4 (distance of rear element + result):

0 cm ~ 1740 nSv/h
5 cm ~ 630 nSv/h
10 cm ~ 420 nSv/h
20 cm ~ 280 nSv/h
40 cm ~ 180 nSv/h (similar level to normal background)

test repeated with rear-cap (plastic) on:

0 cm ~ 1460 nSv/h
5 cm ~ 620 nSv/h
10 cm ~ 310 nSv/h
20 cm ~ 210 nSv/h
40 cm ~ 180 nSv/h (similar level to normal background)

Takumar + both caps + soft lens case + piece of cloth between lens and dosimeter + 10cm distance (to simulate carying the lens in photo-bag): 330 nSv/h

I'm not a physicis, but I think that means, that during a 3-hour trip with Takumar you'll get as much radiation as on 5-hour trip without it(?)

So... if you won't store the Takumar under your bed (or less than 40cm to your body), it shouldn't affect you...


PostPosted: Fri Feb 26, 2010 11:13 pm    Post subject: Reply with quote
no-X wrote:
Sevo: Thanks

other data:

1m distance from my lens cabinet (closer to the place where are 35+50mm lenses): 200 nSv/h

similar measurement in another room: 170 nSv/h


S-M-C Takumar 50/1.4 (distance of rear element + result):

0 cm ~ 1740 nSv/h
5 cm ~ 630 nSv/h
10 cm ~ 420 nSv/h
20 cm ~ 280 nSv/h
40 cm ~ 180 nSv/h (similar level to normal background)

test repeated with rear-cap (plastic) on:

0 cm ~ 1460 nSv/h
5 cm ~ 620 nSv/h
10 cm ~ 310 nSv/h
20 cm ~ 210 nSv/h
40 cm ~ 180 nSv/h (similar level to normal background)

Takumar + both caps + soft lens case + piece of cloth between lens and dosimeter + 10cm distance (to simulate carying the lens in photo-bag): 330 nSv/h

I'm not a physicis, but I think that means, that during a 3-hour trip with Takumar you'll get as much radiation as on 5-hour trip without it(?)

So... if you won't store the Takumar under your bed (or less than 40cm to your body), it shouldn't affect you...


Thanks, that is good information !


PostPosted: Fri Feb 26, 2010 11:35 pm    Post subject: Reply with quote
Orio wrote:
Nox lists background level at about 200. The SMC Tak 1.4/50 is almost 2000 which means 10 times more the background level.
I would not feel safe to have around all the time something that is 10 times more radioactive than normal.


Yes, but 10 x virtually nothing = virtually nothing.


PostPosted: Fri Feb 26, 2010 11:40 pm    Post subject: Reply with quote
peterqd wrote:
Orio wrote:
Nox lists background level at about 200. The SMC Tak 1.4/50 is almost 2000 which means 10 times more the background level.
I would not feel safe to have around all the time something that is 10 times more radioactive than normal.


Yes, but 10 x virtually nothing = virtually nothing.


Well, I know very little about radioactivity, but one of the few things I learned is "there is no such thing as 'nothing' when you speak of radiations".

So, your equation is not true. Especially because it's not a one-time event. A person who owns radioactive lenses uses them more than one time. And another thing I know about radiations is, their effect is cumulative.

-


PostPosted: Sat Feb 27, 2010 12:13 am    Post subject: Reply with quote
The effect of radiation isn't cumulative, the chances of it affecting you are.

You're talking about whether a high energy particle happens to knock a bit of your DNA about. If a collision (or miss) doesn't do damage then it doesn't increase the risk of the next collision doing damage. If you walk away from the source before it damages you, then you should be OK.

However, if you increase the number of collisions five-fold then you have five times the chance of getting one that is damaging.

But this also means that the first collision might be the one that does the harm .... or you might get lucky and have n-billion that don't hurt you.

The risk that the first particle might just be the harmful one is the reason there is not a safe level for radiation. It's not the same as a chemical poison where a certain dosage is always harmless and a certain overdose always lethal.


PostPosted: Sat Feb 27, 2010 12:19 am    Post subject: Reply with quote
PaulC wrote:

However, if you increase the number of collisions five-fold then you have five times the chance of getting one that is damaging.
But this also means that the first collision might be the one that does the harm .... or you might get lucky and have n-billion that don't hurt you.


Yes, but you will agree that increasing the percentage of chances, although it does not increase the certainties either way, is yet a real computable risk, not only a virtual risk.

OK, we are not going to give up our beloved lenses anyway, so I reckon this is just virtual talk Laughing


PostPosted: Sat Feb 27, 2010 12:32 am    Post subject: Reply with quote
Orio wrote:
PaulC wrote:

However, if you increase the number of collisions five-fold then you have five times the chance of getting one that is damaging.
But this also means that the first collision might be the one that does the harm .... or you might get lucky and have n-billion that don't hurt you.


Yes, but you will agree that increasing the percentage of chances, although it does not increase the certainties either way, is yet a real computable risk, not only a virtual risk.

OK, we are not going to give up our beloved lenses anyway, so I reckon this is just virtual talk Laughing


Last thing what we need to worry about radioactivity of our lenses.


PostPosted: Sat Feb 27, 2010 12:57 am    Post subject: Reply with quote
Can somebody confirm, does radiation affect film? Would a radioactive lens fog it?


PostPosted: Sat Feb 27, 2010 1:11 am    Post subject: Reply with quote
no-X wrote:


test repeated with rear-cap (plastic) on:

0 cm ~ 1460 nSv/h
5 cm ~ 620 nSv/h
10 cm ~ 310 nSv/h
20 cm ~ 210 nSv/h
40 cm ~ 180 nSv/h (similar level to normal background)



I just measured the distance from my bed and my Taks... its 1.06m !!!! .
I's safe then , I feared for the worst side-effects possible:



PostPosted: Sat Feb 27, 2010 8:48 am    Post subject: Reply with quote
aleksanderpolo wrote:

Joking aside, do you have experience of how long it takes to "de-yellow" the lens with UV treatment? .


I "bleached" a Nikkor 35/1.4, which had a brown tint, under a 15 watt UV lamp. It took about 800 hours in total -- I turned it around every now and then, as I wasn't certain which element contained thorium, and whether baking the front or the back would be more effective. In any case, after that the colouring had for all intents and purposes gone.

That particular Nikkor radiated about 30x the background radiation in the place where I live, but prolonged exposure to radon is a much more serious health risk here than a few gamma rays from an old lens every now and then.


PostPosted: Sat Feb 27, 2010 8:56 am    Post subject: Reply with quote
peterqd wrote:
Can somebody confirm, does radiation affect film? Would a radioactive lens fog it?

A forum member mentioned, that he got a spotmatic camera with S-M-C 50/1.4, which contained film and wasn't used for tens of years and the film wasn't exposed by the radioactivity. It seems, that the level beyond shutter curtain is so low, that it can't even expose the film...

I think psychical stress from this radioactivity is more dangerous than the radioactivity by itself Smile I believe, that usage of energy-saving bulbs is more dangerous, because when does it break, it contamines the flat by dangerous level of mercury vapours for 2 weeks...


PostPosted: Sat Feb 27, 2010 9:10 am    Post subject: Reply with quote
peterqd wrote:
Can somebody confirm, does radiation affect film? Would a radioactive lens fog it?


Almost certainly not a problem. Lens designers must have known about the radiation levels and taken account of any film sensitivity issues.

You also have different kinds of radiation - alpha and possibly beta would be unlikely to get as far as the film, with the shutter and rear lens in the way.

Ordinary films can survive most airport scanners, though perhaps not as well as the airports like to pretend, so I doubt that very low dose gamma radiation would have much effect.


PostPosted: Sat Feb 27, 2010 10:21 am    Post subject: Reply with quote
Nice job! Even more pleased that your mesurement of the Yashinon 55/1.2 is on par with mine!


PostPosted: Sat Feb 27, 2010 11:57 am    Post subject: Reply with quote
no-X wrote:

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.


Thorium dioxide is radioactive - all lenses with it are radioactive. Lanthanum, on the other hand, is not radioactive (well, the isotope that consists of more than 99% of all lanthanum). If a lanthanum lens shows signs of radioactivity, it may be cause of impurities in the lens (either radioactive lanthanum isotope, or maybe a tiny bit of thorium).

Anyhow, very interesting tests - thank you for them! You made me really want to get a Pancolar 55/1.4 Smile


PostPosted: Sat Feb 27, 2010 12:03 pm    Post subject: Reply with quote
no-X wrote:
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.


Or maybe just within measuring errors? Or did you somehow eliminate the background radioactivity from your measurements?

About that Radex RD1503, it seems to not be sensitive to alpha radioation - understandable as it is not usually dangerous - however, for example the radioactivity of thorium is mainly alpha radiation, if I remember it right.

Again, very interesting measuruments you made!


PostPosted: Sat Feb 27, 2010 12:48 pm    Post subject: Reply with quote
Alpha particles should be blocked already by the lens elements, shouldn't they?


PostPosted: Sat Feb 27, 2010 1:56 pm    Post subject: Re: Radioactivity of old manual lenses Reply with quote
no-X wrote:
I prepared a test of radioactivity on majority of my lenses.


I'm late to this thread, but many thanks for posting! Too bad so few turned out radioactive; public knowledge of the radioactivity of good lenses might lower their prices… =)


PostPosted: Sat Feb 27, 2010 2:02 pm    Post subject: Reply with quote
Hmm, I could switch results of 55/1.4 Pancolar with the APO Lanthar Wink


PostPosted: Sat Feb 27, 2010 2:12 pm    Post subject: Reply with quote
PaulC wrote:
peterqd wrote:
Can somebody confirm, does radiation affect film? Would a radioactive lens fog it?


Almost certainly not a problem. Lens designers must have known about the radiation levels and taken account of any film sensitivity issues.

You also have different kinds of radiation - alpha and possibly beta would be unlikely to get as far as the film, with the shutter and rear lens in the way.

Ordinary films can survive most airport scanners, though perhaps not as well as the airports like to pretend, so I doubt that very low dose gamma radiation would have much effect.


Thanks, I don't understand radiation but that confirms my gut feeling. What is roughly the level of radiation when going through the airport scanner (in figures I can compare with no-x's)?


PostPosted: Sat Feb 27, 2010 2:19 pm    Post subject: Reply with quote
Some comparable values:

Tooth XRay: 10µSv
Thorax XRay: 20-80µSv
Flight at about 30.000ft height: 9µSv/h
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