Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
05-10-2009, 10:35 AM   #1
Inactive Account




Join Date: Oct 2007
Location: Hódmezővásárhely, Hungary
Posts: 9
Once again about Super Multi Coated Takumar 50mm f 1.4

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!



05-10-2009, 10:56 AM   #2
Veteran Member
Stratman's Avatar

Join Date: Mar 2007
Location: St Louis, Missouri U S A
Photos: Gallery | Albums
Posts: 2,464
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







05-10-2009, 11:10 AM   #3
Senior Member
rpriedhorsky's Avatar

Join Date: Dec 2008
Location: Minneapolis
Posts: 210
QuoteOriginally posted by Buksikoma Quote
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).
05-10-2009, 11:44 AM   #4
Veteran Member




Join Date: Feb 2009
Location: Portland, OR
Photos: Albums
Posts: 325
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?

05-10-2009, 12:08 PM   #5
Site Supporter
Rense's Avatar

Join Date: Dec 2008
Location: Zetten - The Netherlands
Photos: Gallery | Albums
Posts: 8,812
QuoteOriginally posted by jmbradd Quote
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
05-10-2009, 04:09 PM   #6
Dom
Guest




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.
05-10-2009, 09:00 PM   #7
Pentaxian
mikeSF's Avatar

Join Date: Jan 2009
Location: East Bay Area, CA
Photos: Gallery
Posts: 5,541
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?
05-10-2009, 09:02 PM   #8
Veteran Member
Andi Lo's Avatar

Join Date: Jul 2008
Location: Halifax, Nova Scotia
Posts: 2,925
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.

Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
50mm, iq, k-mount, lens, lenses, m42, multi coated takumar, pentax lens, radiation, slr lens, takumar, takumar 50mm, thorium
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale - Sold: Super-Multi-Coated Takumar 50mm 1:1.4 k100d Sold Items 27 08-24-2009 09:17 PM
Super Multi Coated Takumar 50mm f4 k100d Post Your Photos! 4 03-21-2008 04:38 AM
For Sale - Sold: Super-Multi-Coated Takumar 50mm 1.4 ,65$ mayoapo Sold Items 0 08-26-2007 09:38 AM
For Sale - Sold: Super-Multi-Coated Takumar 50mm f: 1.4 mayoapo Sold Items 0 08-19-2007 11:48 PM



All times are GMT -7. The time now is 08:02 AM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top