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07-13-2015, 02:40 PM - 1 Like   #1
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55mm 1.8 takumar radiation anxiety.

Hello. i am a new member of the forum. I was looking for a takumar 55mm 1.8 lens to buy to use adapted with my mirrorless camera. Anyways after doing a bit of research i learned that the lenses are radioactive. This of course worries me because radiation can't be good. I read about the coatings being radioactive and that they emit gamma rays, which in my understanding of radiation is the worst kind. I haven't been able to find a clear answer on whether they are safe or not. I then read that some of the 55mm takumars are less radioactive then others. Which version is the least radioactive. Also, i heard the earliest version does not have radioactive materials in them, but i am not sure. I would appreciate if someone here can help me get the facts straight. Thank you

07-13-2015, 02:52 PM   #2
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the level of radiation is insignificant. you should not worry. enjoy the lens, it is great.
07-13-2015, 02:57 PM - 1 Like   #3
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The issue of radioactive lenses, both elements and coatings is of no risk to the user. Now considering the poor workers who handled the materials, and perhaps were exposed to dust from lens polishing etc, that's a different story.

It is the same with many many manufactured products, the issue is the exposure to workers during manufactur, and to a lesser degree upon disposal to the environment, but not to the user.
07-13-2015, 02:59 PM   #4
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Is there any evidence at all, other than questionable youtube videos, that the 55/1.8 is thoriated?

AFAIK the only 135 Takumars that are thoriated are the 50/1.4 (7-element) and the 35/2 (49mm filter).

07-13-2015, 03:16 PM   #5
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QuoteOriginally posted by boriscleto Quote
Is there any evidence at all, other than questionable youtube videos, that the 55/1.8 is thoriated?

AFAIK the only 135 Takumars that are thoriated are the 50/1.4 (7-element) and the 35/2 (49mm filter).
This is where i saw someone saying the 55mm 1.8 is thoriated and someone also said it isn't so i cant really get a consensus because everyone says something different. Here is the link to the forum where i saw this

SMC Takumar 55 f1.8 radioctive?

Thank you
07-13-2015, 03:20 PM   #6
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My personal view is that people overly gloss over this issue. There are opinions like this one: A Look at the Radioactivity of Old Manual Lenses that seem well informed and suggest that even heavy use is not a big risk.

This site on a different set of lenses includes a great deal of info on why the lenses are radioactive:
Aero-Ektar Lenses

Another...
Thoriated Camera Lens (ca. 1970s)

I did read a few negative ones that were well informed also. Those are eluding me - in essence they found that some lenses emitted enough to make x-ray technicians get concerned about long term risks. It has been too long since I researched this and I can not find any right now.

Bottom line - your mileage may vary...
07-13-2015, 03:27 PM   #7
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also, does the yellowing have anything to do with it being radioactive? The one lens i was planning on buying is only yellow colored at the front element, so does this mean it is just a front element coating? The serial number starts with 153. if this can determine whether its radioactive that would be good. Thanks

07-13-2015, 03:36 PM   #8
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QuoteOriginally posted by dcshooter Quote
The 55mm f/1.8 is routinely encountered yellowed, so it is safe to say it has thorium elements.

That says, Thorium is only mildly radioactive and primarily emits alpha radiation (not gamma radiation) which has trouble even penetrating human skin and can be handled safely.

One of its decay products is radon gas, which is more dangerous, but in the miniscule amounts released by the tiny amount of thorium in the glass, it poses basically no danger, since the gas just disperses into the atmosphere as it is produced.

Basically, you'd have to eat the lens element for it to be of any significant danger, and the camera body you hold between the lens and your face mean that you are shielded from pretty much any exposure while using it.

And yes, I have received radiological safety training.



---------- Post added 07-13-15 at 03:32 PM ----------

Also note: The Miller analysis is based on surface measurements and doesn't take into account the shielding action of a metal camera body between the lens and your body.


So you saying that you have radiological safety training mean you have a good understanding of radiation and what it does to us?
07-13-2015, 03:44 PM   #9
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QuoteOriginally posted by boriscleto Quote
s there any evidence at all, other than questionable youtube videos, that the 55/1.8 is thoriated?
Yes, though the radiation level is lower (about 65% of) than the ST 50/1.4, but present. Here is a reference with actual measurements:

https://www.flickr.com/photos/s58y/6802092736

FWIW, I have two ST 55/1.8 and neither has sufficient radiation to cause yellowing. I also have a Auto-Rikenon 55/1.4 that is on the 'hot' list and which has significant yellowing.


Steve
07-13-2015, 04:06 PM - 1 Like   #10
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QuoteOriginally posted by dcshooter Quote
Thorium is only mildly radioactive and primarily emits alpha radiation (not gamma radiation)
Emits alpha particles with accompanying gamma radiation, though the risk from either is low unless the thorium is eaten or inhaled. All that being said, no discussion of thoriated lenses would be complete without mentioning that the most common source of exposure to significant amounts of thorium would be through the mantles used with gas lanterns. Lesson of the day: Do not eat or inhale lantern mantles!!


Steve

Last edited by stevebrot; 07-13-2015 at 04:20 PM.
07-13-2015, 04:10 PM - 3 Likes   #11
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I have the 50 and 55. Except for some mild blistering in and around the right eyebrow I have noticed no ill effects.
07-13-2015, 04:18 PM - 1 Like   #12
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QuoteOriginally posted by condor27596 Quote
Except for some mild blistering in and around the right eyebrow I have noticed no ill effects.
Is that because you were trying to mount the lens onto your eye?

OP: I have a Takumar 50/1.4. I did extensive research into the radiation question. As an engineer, I understand the physics and implications (not trying to boast) - I don't have any worries, and use the lens regularly.

Enjoy your lens! Takumars are wonderful. The Tak 55/1.8 is particularly sharp.

- Craig

Last edited by c.a.m; 07-13-2015 at 04:23 PM.
07-13-2015, 05:33 PM   #13
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I really enjoy the auto-takumar 55mm line (apertures range from 1.8-2.2, all essentially the same lens though). It has absolutely no radioactive elements, but the same wonderful rendering. It has no coating (stated at least), but I actually appreciate that on these old lenses. It comes with a fun aperture lever to boot.
07-13-2015, 05:34 PM   #14
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QuoteOriginally posted by condor27596 Quote
I have the 50 and 55. Except for some mild blistering in and around the right eyebrow I have noticed no ill effects.
I have had all the Thoriated lenses mentioned in the internet literature since they were released. It took 50 years for the vision in my right eye to degrade so much that I had to switch to left-eye shooting.
07-13-2015, 06:17 PM   #15
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You'd be exposed to more radiation on a single air flight than a lifetime for a lens or even a radium watch from yesteryear.

Heck, if you live in Denver, you get even more radiation than that on a daily basis from the granite.
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