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Radioactivity of old manual lenses
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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.


PostPosted: Sun Feb 28, 2010 3:50 pm    Post subject: Reply with quote
The Aero Ektar positively has a thoriated last element - but at more than 15cm to the film plane, even air is a pretty good alpha particle barrier, and the law of squares does the rest, so that nobody has reported lens related fogging so far (even though many people have tried to provoke it).

But short focal length lenses with a thoriated inner element should fog the film fairly soon - any smart lens designer will have put at least one other element between the thoriated and film if the distance is critical, so that such a lens probably does not exist...


PostPosted: Sun Feb 28, 2010 4:21 pm    Post subject: Reply with quote
Anu wrote:
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.

Really, I don't know. Some lenses shows much stronger radioactivity from the rear side, others not.

Here is ratio of rear : front radioactivity:

Tomio 55/1.2: 3 : 1
S-M-C 50/1.4: 2.8 : 1
S.Tak 35/2.0: 2 : 1
S-M-C 35/2.0: 1.8 : 1
C.Z.J. 55/1.4: 1.4 : 1
S-M-C 50/4.0: 1 : 1
C.Z.J. 85/2.8: 1 : 1.2
S-M-C 85/1.8: 1 : 3.3


We know, that the radioactive element in Takumar 50/1.4 isn't the last one (7th), because some members confirmed, that extraction of the radioactive element speeds up UV bleaching, because the UV rays aren't blocked by rear (7th) element. So it can be the 5th or 6th one.

It's likely in relation to Tomioka 55/1.2, too.

For S-M-C 85/1.8 it seems, that the hot element is 1st or 2nd one... More likely the 2nd one to prevent cremation of the portraited model Smile


PostPosted: Mon Mar 01, 2010 12:50 pm    Post subject: Reply with quote
One interesting thing: fungus doesn't care a bit about radioactivity Smile. I found Takumars especially prone to spores growth.

Hey No-X do you happen to own any of those XR-Heligons - could you please measure them?


PostPosted: Tue Mar 02, 2010 4:31 pm    Post subject: Reply with quote
Pancolart wrote:
One interesting thing: fungus doesn't care a bit about radioactivity Smile. I found Takumars especially prone to spores growth.

Hey No-X do you happen to own any of those XR-Heligons - could you please measure them?


We could end up with a mutant mushroom from hell called Takzilla. Laughing


PostPosted: Tue Mar 02, 2010 4:51 pm    Post subject: Reply with quote
Pancolart: Sorry, I don't have these lenses...


PostPosted: Tue Mar 02, 2010 5:17 pm    Post subject: Reply with quote
Pancolart wrote:
Hey No-X do you happen to own any of those XR-Heligons - could you please measure them?


I don't have XR-Heligons either, but I do have one De Oude Delft 50/0.75. That didn't give any reading discernible from background radiation.


PostPosted: Tue Mar 02, 2010 6:36 pm    Post subject: Reply with quote
With these lenses i am not afraid of radiation due to materials used but more as a consequence of use in x-ray machines, synchrotron and tomography. I know practically nothing of that stuff and i am waiting for a pack of such lenses available as industrial waste. I am a bit scared Smile. Anyone noticed it's hard to import them from USA to EU?


PostPosted: Sat Mar 13, 2010 8:57 pm    Post subject: Reply with quote
for Orio: not only lenses are radioactive:

http://www.orau.org/PTP/collection/consumer%20products/consumer.htm


you should also beware of Playboy magazine Very Happy

http://www.orau.org/PTP/collection/consumer%20products/magazines.htm


PostPosted: Sat Mar 13, 2010 9:13 pm    Post subject: Reply with quote
Rokkfish wrote:
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?


Yeah, since the thorium apparently won't give us cancer, why not let UV take care of that, too? Very Happy


PostPosted: Sat Mar 27, 2010 10:13 pm    Post subject: Reply with quote
Hi all, I'm new here
reading about radioactivity ...I'm scared about, because from 1 year I've worked on different old lenses, and seeing through old yellowish elements and reading around, I don't know if can cause problem ...even when cleaning can be risk of dust and particles, breath or eat...???

...any advise?

Thanks


PostPosted: Sat Mar 27, 2010 10:25 pm    Post subject: Reply with quote
There seems to be no significant risk at all. I wouldn't worry about it.


PostPosted: Sat Mar 27, 2010 10:42 pm    Post subject: Reply with quote
Thorium glass was dangerous only for the pleople in factories, who grinded it. The dust got into their lungs and... well... radioactive dust emitting alpha and beta particles directly on mucous tissue isn't very healthy... But for users it isn't risky. Dangerous alpha and beta particles are filtered by the lens body and other glass elements.


PostPosted: Sun Mar 28, 2010 10:55 am    Post subject: Reply with quote
Thanks a lot...Smile

then if I continue to disasembly elements for cleaning, I only have to be careful to don't crack, scratch etc... I only use solvents to clean, with gloves...

Even coatings were made with radioactive chemical/materials?


PostPosted: Sun Mar 28, 2010 11:03 am    Post subject: Reply with quote
No, coating (at least on common lenses) isn't radioactive.


PostPosted: Tue May 18, 2010 1:23 pm    Post subject: Reply with quote
francotirador wrote:

Do you know about [the radioactivity of] Minolta Rokkor PG 58mm f 1.2?


Mine is radioactive. The radioactive glass is definitely on the rear side of the lens, and measures slightly less radioactive than the S-M-C Takumar 50mm f/1.4.

Mine is the oldest version of this lens, don't know if this applies only to that or to all versions.


PostPosted: Tue May 18, 2010 2:10 pm    Post subject: Reply with quote
I wonder if it's always affects the sensor in the camera, refer to the rokkor 58/1.2 PG
Rolling Eyes


PostPosted: Tue Jun 22, 2010 10:42 am    Post subject: Reply with quote
Do you know where can i borrow Geiger counter? I mean which companies / organizations tends to have it?


PostPosted: Tue Jun 22, 2010 11:19 am    Post subject: Reply with quote
The good ones are expensive...

Perhaps a local university?


PostPosted: Tue Jun 22, 2010 2:06 pm    Post subject: Reply with quote
Good idea, I also went to the physics department of our local university after having asked a professor, if he can check my lenses with his Geiger counter. One day later he checked my lenses, which were fortunately NOT hot and got a private lecture about physics in everyday life. Smile

I followed different discussions about radioactive lenses with all the typical pros and cons. After all I think that using thoriated lenses is a risk you should avoid because of health reasons as a result of Alpha radiation.

Regards

Lichtstrom


PostPosted: Tue Jun 22, 2010 2:22 pm    Post subject: Reply with quote
If you are worry sell them , somebody will take them happily.
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