Originally posted by séamuis I'm not so sure that Asahi Optical never used any thoriated glass in any of the 55's. the truth is we don't actually know what Asahi Opt. did and didn't do, and while I believe there is no known official documents or otherwise showing that they did or didn't, there are a number of people who have had examples of 55's with what have at least looked like yellowed glass. I would say, we should never rule out the possibility that at least there are some 55's out there with thoriated glass, unless someone can prove pretty assuredly that Asahi Opt. never used any thoriated glass elements in any lenses other than the non-8 element 50mm 1.4's.
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