[Buksikoma]

Hello!

Being intended to buy a fast M42 standard lens with highly rated IQ I'd like to ask 4 question about the Super Multi Coated Takumar 50mm f 1.4:

1. Probably it is rather hard to find any people around being not aware of the fact that this lens shows some radioactivity as a result of the thorium content of the coating. It is also known that "this radiation is not dangerous for human healthy". I'd like to know if there is anyone who could support this reassurance statement with numbers or medical expertise?

2. Where can I see about which other old lenses are radioactive? I've tried it but haven't managed to find the right pages so far, perhaps it is a mistake of my google search engine...

3. The yellowing of this lens is also a well known and frequently occurrence which is a result of the thorium radiation. Now supposing that in eBay I can see one which has no yellowing. Does it mean that it will never have or the yellowing is only a matter of time?

4. Are there any M42 fast high IQ lenses at about 50-60 mm which can reach the performance of this Takumar? Bookeh and sharpness - in this order - are the most important features for me.

Many thanks!

[Stratman]

The 55 1.8 is nothing to sneeze at for sure, and you should be able to find one dirt cheap !!

A few from the Super Takumar 55mm f1.8

[rpriedhorsky]

1. Probably it is rather hard to find any people around being not aware of the fact that this lens shows some radioactivity as a result of the thorium content of the coating. It is also known that "this radiation is not dangerous for human healthy". I'd like to know if there is anyone who could support this reassurance statement with numbers or medical expertise?

You get substantial doses of radioactivity from being alive, mostly due to natural causes. It's impossible to avoid and there's no point in trying.

I don't know how radioactive SMC Taks are, but surely you can Google it. Take those numbers and compare them with this computation of your background dose. I think you could probably store your Taks inside your lungs and be just fine.

Bananas are measurably radioactive, too (from the potassium-40 IIRC).

[jmbradd]

so then I guess briefcase filled with the entire line of SMC Takumar lenses and a ton of bananas might give airport security the wrong idea?

[Rense]

so then I guess briefcase filled with the entire line of SMC Takumar lenses and a ton of bananas might give airport security the wrong idea?

Yeah, and for more than one reason I guess

Having just checked my Open University data book.

Thorium has a half-life 14 billion years, which means that it decay very very slowly. emitting a alpha particle. A single sheet of paper stops a alpha particle.

You would have to eat the lens to cause any sort of health issues but I thing the broken glass would be more of an issue.

It's about as radioactive a soil.

As for other fast M42 50mm, have a look at Zeiss lenses. I've got a Tessar 50mm f2.8 and it's lovely.

[mikeSF]

this is from Wikipedia.com:

Precautions
Powdered thorium metal will often ignite spontaneously in air (it is pyrophoric) and should be handled carefully.

Natural thorium decays very slowly compared to many other radioactive materials, and the alpha radiation emitted cannot penetrate human skin. Owning and handling small amounts of thorium, such as a gas mantle, is considered safe if care is taken not to ingest the thorium -- lungs and other internal organs can be penetrated by alpha radiation. Exposure to an aerosol of thorium can lead to increased risk of cancers of the lung, pancreas and blood. Exposure to thorium internally leads to increased risk of liver diseases. This element has no known biological role. See also Thorotrast.


[edit] Thorium extraction
Thorium - Wikipedia, the free encyclopedia

not enough radiation to thwart my LBA for Takumars...i mean, i only have one at the moment; how do i get by?

[Andi Lo]

Tak 50 is the best lens I own. I know this claim is useless without pics. Will get some when I get back later

Can't answer question 1-3 but as for question 4, I don't think there's a lens that's as good as the 50/1.4 in the same price league. I've heard about Voigtlander lenses having better performance than the Tak, though.