[Clanky44]

Hello folks,

I am new to mirrorless cameras, having picked up a Fuji x-t2 just a few months ago. I've started to look at some vintage m42 mount lenses to experience the artistic side these lenses have to offer. As I was watching some reviews, my wife pointed out that her father had left her some vintage cameras in a box somewhere in the basement,... a bit of a search found a small box with mostly useless just point and shoots, but there's was a Pentax Asahi film camera with an SMC TAKUMAR 1:2 55mm Asahi lens. Serial # 7624832. The lens has a distinctive yellow tinge with a bit of exterior lens dust but shows no wear on it.

Is there any way to confirm if this lens has the thorium glass in it? I've heard differing accounts to the dangers of using the radioactive lenses,.. from 'avoid at all costs' to 'it's the price you pay for great images'... My wife wants to throw out the lens already ?.. I've placed an order for an m42 Fuji mount.

[Adam]

Hello folks,

I am new to mirrorless cameras, having picked up a Fuji x-t2 just a few months ago. I've started to look at some vintage m42 mount lenses to experience the artistic side these lenses have to offer. As I was watching some reviews, my wife pointed out that her father had left her some vintage cameras in a box somewhere in the basement,... a bit of a search found a small box with mostly useless just point and shoots, but there's was a Pentax Asahi film camera with an SMC TAKUMAR 1:2 55mm Asahi lens. Serial # 7624832. The lens has a distinctive yellow tinge with a bit of exterior lens dust but shows no wear on it.

Is there any way to confirm if this lens has the thorium glass in it? I've heard differing accounts to the dangers of using the radioactive lenses,.. from 'avoid at all costs' to 'it's the price you pay for great images'... My wife wants to throw out the lens already ?.. I've placed an order for an m42 Fuji mount.

The only way to confirm would be to measure the actual radiation, but I do believe the 55mm F2 is known to be radioactive. That said, I really don't think it's a concern in normal use.

How radioactive are the Super Takumars? - PentaxForums.com

[Ned Bunnell]

Greetings,
You’ve gotten a lot of great advice. I posted a series of images detailing how I treated one of my Tak’s last year on Instagram. I thought some of this information might be helpful. Enjoy your Tak, it’s a beautiful lens.
Cheers,
Ned

Two Tak’s after CLA:
Ned Bunnell on Instagram: ?07.29.17 Super Takumar 50mm f/1.4 (7 element) lenses. Photo 1 of 2. I just got these back from being CLA'd. They're both in mint condition.??

Degree of Thorium Fogging:
Ned Bunnell on Instagram: ?07.29.17 Super Takumar 50mm f/1.4 (7 element) lenses. Photo 2 of 2. I just got these back from being CLA'd. Thorium fogging on earlier??

UV Treatment:
Ned Bunnell on Instagram: ?08.03.17 My big science project. I'm using the Ikea JANSJÖ LED work lamp (see comment below about UV) to see how it reduces the Thorium??

Results of UV Treatment:
Ned Bunnell on Instagram: ?08.05.17 Update on using the Ikea JANSJÖ LED work lamp to see how it reduces the Thorium fogging on one of my Super Takumar 50mm f/1.4 (7??

Tip about front element:
Ned Bunnell on Instagram: ?08.07.17 As a final tip if you're considering buying a Super Takumar 50mm f/1.4 or most early Tak lenses...The Thorium coating was only??

[stevebrot]

Welcome to the Pentax Forums!

The only way to confirm would be to measure the actual radiation, but I do believe the 55mm F2 is known to be radioactive.

Yes, this is true on both counts, though, as with the Super Takumar 55/1.8, there might be some Super Takumar 55/2.0 examples that don't have radioactive thorium doped glass. The yellow-brownish discoloration (found on the rearward elements) is a good indication, however.

Results of UV Treatment:
Ned Bunnell on Instagram: ?08.05.17 Update on using the Ikea JANSJÖ LED work lamp to see how it reduces the Thorium fogging on one of my Super Takumar 50mm f/1.4 (7??

I too favor the Ikea JANSJÖ lamp for dealing with the yellowing. It works like a charm. As for the radiation, it is unlikely that your lens would cause health problems if used as intended. The is particularly true if it is mounted to a camera and/or is not stored in close proximity to you or a family member. Use of a metal rear cap might also decrease emissions, though I have no data on that.


Steve

[Clanky44]

Thank you all for the replies.

One potential issue I couldn't find in the links is the effect of long term radiation on the sensor. I'd assume it best to remove the lens from the x-t2 when not in use.