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Radioactivity of old manual lenses
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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


PostPosted: Sat Feb 27, 2010 2:30 pm    Post subject: Reply with quote
no-X wrote:
Alpha particles should be blocked already by the lens elements, shouldn't they?


Yes, but thorium decays into other radioactive elements that emit beta and gamma just as well when they decay.


PostPosted: Sat Feb 27, 2010 2:32 pm    Post subject: Reply with quote
I measured MC Biometar 80/2.8 P6 - it isn't radioactive. But the zebra model is. How could it be? Maybe the case of impure lanthanum in the older model?


PostPosted: Sat Feb 27, 2010 2:46 pm    Post subject: Reply with quote
no-X wrote:
I measured MC Biometar 80/2.8 P6 - it isn't radioactive. But the zebra model is.


I previously understood it was the other way around?
I am confused.


PostPosted: Sat Feb 27, 2010 2:59 pm    Post subject: Reply with quote
In the table there are:

Biometar M42 alu - not radioactive
Biometar P6 zebra - radioactive

today I measured:

Biometar P6 MC - not radioactive

Only zebra radiates...


PostPosted: Sat Feb 27, 2010 4:06 pm    Post subject: Reply with quote
My P6 Biometar zebra has very weak yellowing. It will be going under the black light shortly following the Super Tak 50mm f1.4.
bb2


PostPosted: Sat Feb 27, 2010 9:40 pm    Post subject: Reply with quote
Cobalt60 wrote:
Some comparable values:

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


It may be necessary to point out that you are giving figures in micro sieverts, which are 1,000 times bigger than the nano sieverts in the original test.
So the worst of the lenses is only coming in at the equivalent of a fifth of a tooth X-ray. You would have to sit very close to the lens for five solid hours before collecting the dosage from one x-ray. (Probably more like six or seven hours, because I forgot to deduct the background radiation, which isn't the lens's fault).

You are also at around a fifth of the exposure rate from flying and it is reckoned that professional airline pilots have about a 1% increased cancer risk as a result of their work. You would therefore have to hug your lens for five times as long as an airline pilot spends flying (which is approx 65 hours per month) to match that 1% increased cancer risk. Twelve hours a day for 30 years would probably be the equivalent.

Assuming I've got all the figures right, of course.


PostPosted: Sat Feb 27, 2010 11:49 pm    Post subject: Reply with quote
PaulC wrote:
Cobalt60 wrote:
Some comparable values:

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


It may be necessary to point out that you are giving figures in micro sieverts, which are 1,000 times bigger than the nano sieverts in the original test.

Thanks to you both, now we can put things in perspective, so to speak. I managed to work out the 1/1000 factor myself! Smile


PostPosted: Sun Feb 28, 2010 12:28 am    Post subject: Reply with quote
In terms of clearing the yellow cast: what about using a UV salon sunbed? That way you can get a cheap tan and surround yourself with your favorite little friends at the same time! Or how about a cheap sunlamp?


PostPosted: Sun Feb 28, 2010 6:00 am    Post subject: Reply with quote
Pretty good work NO-X. Thank you.
Do you know about Minolta Rokkor PG 58mm f 1.2?


PostPosted: Sun Feb 28, 2010 3:41 pm    Post subject: Reply with quote
no-X wrote:
Alpha particles should be blocked already by the lens elements, shouldn't they?


Yes, but I though that the last element is often among the juiced ones. I may be wrong though.
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