Originally posted by stevebrot I researched this matter several years ago and based my comment partially on that research and partially on what I have been by various camera buffs, repair people and such. If the 55/1.8 has the yellowing problem, it was new to me.
On the other hand, I have long suspected that the lists (including the one linked several comments above) are far from complete. I just did a little Google work and was surprised to find videos of people testing lenses that I would never have dreamed were radioactive. Based on that search it appears that these lenses were quite common. The big surprises? How do these sound:
- Yashinon DX 35/1.8 (on Electro 35 CC)
- Various Super-8 movie cameras
- Yashinon DS/DX 50/1.4/1.7
- Mamiya/Sekor 55/1.4
- Leitz Summicron 50/2 (collapsible ca. 1953)
- A plethora of Canon FD/FL fast 50s
- EBC Fujinon 50/1.4
- Various Zeiss Jena
...and yes...at least two (SMC and S-M-C) Takumar 55/1.8.
It almost makes me want to get a cheap geiger counter and head down to check out the shelves at the local used camera places. Seriously though, I own a couple of lenses (non-Pentax fast 50s from the late 60s and my Jupiter-8 in Contax/Kiev) that have a yellowish cast that I would sort of like to test just to satisfy my curiosity.
Steve
Some Pentax 55/1.8 Takumars are radioactive and some aren't. My early 55/1.8 Auto Takumar isn't radioactive at all, but the S-M-C 55/1.8 is about 2/3 as radioactive as the famous 50/1.4 S-M-C Takumar, based on a Geiger-Mueller pancake probe close to the rear element. Farther away, as measured with a "high energy" gamma ray scintillator probe 100mm from the side of the lenses, the 55/1.8 is only about 20% as radioactive as the 50/1.4.
The 55/1.8 is not significantly yellowed, while the 50/1.4 was decidedly yellow, before I gave it the UV treatment.
The most surprising finding with the geiger counter was that the Canon FD 17mm f/4 and Olympus 20mm f/3.5 bellows lenses are both radioactive.
BTW -- Does anyone know of a comprehensive list of thorium-containing lenses?