[zvon]

Perspective:
Nick's Geiger Counter Page
1 micro sievert/Hour is roughly the same as the CPM * 0.0057

This video is of a seven element Takumar 50mm f1.4:
Radioactive Lens -- Pentax 50mm f/1.4 S-M-C Takumar - YouTube
At 51 seconds in the count from the back of the lens is 22000 CPM (the scale indicator is on x1000 in the top of the display)
22000 CPM is roughly 125 micro sievert/hrs.

He later states no alphas, only beta and gamma. The second test tops at around 12000 CPM.

His background radiation measure is around 30CPM = 0.17 micro Sievert/hrs

The point of all this is to reinforce what Steve said, the measured radiation on the 8 element is inconsequential and does not point to the use of thoriated glass.

You can not convert CPM to Sieverts just like that from thin air.... CPM is just counts per minute (conversion to Sv depends on calibration by the known source and radiological equipment used). Question for getting Sievert reading is the energy of the particles in eV that are being emitted by the source. It is true that Thorium-232 used in lens is exclusively alpha source but in the decay chain of thorium-232 you also get Radium down the line, which is beta minus and gamma source. And that by it self means absolutely nothing since everybody is bombarded by gamma every second of their lives.... You have to know the energy of those gamma and beta particles to know if any damage to tissue would be present. and in the case of radium generated in the decay chain of Th is negligible.

It's like headphones, you can get them to generate 120+ dB of sound pressure but range/energy is very low. 7 element taks are capable of generating milisieverts when very very close. But even then it is very localized exposure. You would have to wear the rear element right by your eye for 8 hours a day for 10 years to be able to say that it did something to you like like for eg. cataract (shooting blanks on cataracts...)

[JollyGreen]

I've met a nice person in this community that is selling an 8 Element and mentions that it has "different/older lettering than other copies I have seen" Can you guys take a look at this lens/post and let me know your thoughts? I believe it to be a legit 8 element, as the seller has good standing with this community.


8-element 50mm Super Takumar f1.4 - PentaxForums.com

I appreciate your feedback on the legitimacy and price if it is fair! Also anything about the apparent "abnormal" lettering is appreciated.

[stevebrot]

I've met a nice person in this community that is selling an 8 Element and mentions that it has "different/older lettering than other copies I have seen" Can you guys take a look at this lens/post and let me know your thoughts? I believe it to be a legit 8 element, as the seller has good standing with this community.


8-element 50mm Super Takumar f1.4 - PentaxForums.com

I appreciate your feedback on the legitimacy and price if it is fair! Also anything about the apparent "abnormal" lettering is appreciated.

The lens is legit and the seller is a regular contributor here. As for the lettering, variations on the font are discussed on the Takumar Field Guide site 8-element page...

1 : 1.4 / 50 (358) 8 element - Takumar Field Guide


Steve

[JollyGreen]

The lens is legit and the seller is a regular contributor here. As for the lettering, variations on the font are discussed on the Takumar Field Guide site 8-element page...

1 : 1.4 / 50 (358) 8 element - Takumar Field Guide


Steve

Thanks Steve! I swiped up this lens very quickly, and am super excited to start shooting with it!

[UncleVanya]

You can not convert CPM to Sieverts just like that from thin air.... CPM is just counts per minute (conversion to Sv depends on calibration by the known source and radiological equipment used). Question for getting Sievert reading is the energy of the particles in eV that are being emitted by the source. It is true that Thorium-232 used in lens is exclusively alpha source but in the decay chain of thorium-232 you also get Radium down the line, which is beta minus and gamma source. And that by it self means absolutely nothing since everybody is bombarded by gamma every second of their lives.... You have to know the energy of those gamma and beta particles to know if any damage to tissue would be present. and in the case of radium generated in the decay chain of Th is negligible.

It's like headphones, you can get them to generate 120+ dB of sound pressure but range/energy is very low. 7 element taks are capable of generating milisieverts when very very close. But even then it is very localized exposure. You would have to wear the rear element right by your eye for 8 hours a day for 10 years to be able to say that it did something to you like like for eg. cataract (shooting blanks on cataracts...)

Good info about converting, I assume the site link posted was only referencing their equipment. So we have no way to know how much the cpm count in the video actually represents without clearer data on the exact equipment.

Here's a link I found that clearly agrees with this: How to Measure Radiation - Geiger Counters International

Thanks for correcting my misunderstanding.