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03-04-2010, 10:35 PM   #1
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Are all Takumar 300mm radioactive?


Just wondering. And if they are, how dangerous is a lens of this type. Thanks!

03-04-2010, 11:59 PM   #2
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I have a radioactive 50mm. I have no intention of eating the lens or holding it in direct contact with my body for extended peiods of time so I'm not too concerned about it.
03-05-2010, 12:03 AM   #3
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QuoteOriginally posted by oxidized Quote

Just wondering. And if they are, how dangerous is a lens of this type. Thanks!
They are extremely dangerous, and I have a proper storage facility

Honestly, don't worry about the radiation. You (most likely) receive more from watching the TV
03-05-2010, 05:33 AM   #4
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It's in that big a lens?

There are a lot of threads on this, and the major culprit is a substance called thorium, which found it's way into many Takumar lenses. The thorium has been known to cause a yellow tint in some elements if the lens has been stored away from sunlight for a long period of time. This yellowing in pretty much meaningless in the digital era, but it can be reduced or removed by subjecting the lens to UV light or just sunlight for a long period of time, measured in weeks.

I guess my question on this thread is.... I've heard of radioactive fast 50's and maybe some Tak 35mm lenses, but I've never heard that the nuke glass found it's way into the big Takumar guns, like a 300mm.

Can anyone confirm this?

heh heh ... I always ask the hard questions!



03-05-2010, 06:00 AM   #5
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I have 7 takumars and a geiger counter. I can confirm that:

Super takumar 50mm f/1.4 and 55mm f/1.8 are radioactive.

Super takumar 35mm f/3.5, 55mm f/2, 150mm f/4, 300mm f/4 and smc takumar 135mm f/3.5 are not radioactive.

The radioactive lenses should not pose a danger as long as you don't:
Use them as an eye loupe for extended periods,
Carry them arround in your trouser pocket all day
Sleep with them under your pillow.

As will all radioactive sources you can minimise your dose by limiting your exposure time and by keeping them at a distance (1/r^2 law means that if you double the distance you quarter the dose, if you increase the distance by a factor of 10 you reduce the dose by a factor of 100)

Thoriated glass was used in quite a few lenses of that period as it had a high refractive index and a low dispersion and so was very usefull in correcting chromatic aberations.
The fact that the 55mm f/1.8 is radioactive and the very similar 55mm f/2 is not indicates that although the difference in max aperture is very small the lenses must be slightly different optical designes.

Last edited by MattGunn; 03-05-2010 at 06:07 AM.
03-05-2010, 07:14 AM   #6
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Thanks for all the detailed info!!!
03-05-2010, 08:21 AM   #7
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Those old lenses are great when you you go hiking. You can nuke your food and have a hot lunch.
03-05-2010, 04:39 PM   #8
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Here is something I posted a while back. Thought you might like to know.

In addition to the radioactive problem with the various Takumar lenses there is another problem which is even more dangerous.

In another thread a few months back a user related that he was was changing from an M42 mount to a K mount while standing on the platform of a train station. He dropped the mount adapter, it rolled off the platform, and ended up by the tracks. He jumped down retrieved the mount adapter, and returned to the platform.

The conclusion which I have come to is that in addition to having your eyeball shrivel up and fall out along with the potential loss of teeth and hair from radiation exposure, you also have the possibility of getting run over by a train. These lenses are dangerous and should only be used by a professional. Send all your Takumar lenses to Mike Cash. Mike is really "Mr. Takumar" around here and he will know what to do. You can't be too careful.

Last edited by wlank; 03-05-2010 at 04:50 PM.

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