Yellowing Min 58/1.2 according to S.Kölliker (artaphot.ch)

[Pontus]

http://www.artaphot.ch/nex-lens-comparisons/344-nex-5n-und-minolta-50mm-objektive-teil-i

Very interesting lens tests but what struck me was the following statement: "Bedingt durch ein spezielles Sonderglas hat das 1.2/58mm (ebenso wie das Leitz 1/50mm) einen deutlichen Gelbstich. Dieser Gelbstich ist - anders als z. B. beim Minolta MC 28mm 1:2.5 oder beim Super-Takumar 1.4/50mm - nicht durch radioaktive Gläser verursacht; er kann somit auch durch "Sonnenbaden" nicht ausgebleicht werden!"

According to Stephan, the 58/1.2 is not radioactive and the yellowing cannot be cured with UV light. Comments anyone? This is the first time I have heard about this.

[Pontus]

I'm bumping this thread as I'm afraid that this question will go unanswered otherwise. Please, if you know if Stephan is right, let us know. Have you been able to cure the yellowing of this lens?

[Tervueren]

Can't help I'm afraid, mine suffers from no discoloration at all and to be honest I've never heard it mentioned before

[Minolfan]

[fermy]

Well, his 58/1.2 has clearly yellowed, which can be seen in his samples. The color signature reminds me very much of my thorium Nikkor-N 35/1.4. He doesn't say why he thinks that yellowing is not caused by radiation. If he tried to cure that by exposing to sunlight, but failed, then there is no surprise here. While waiting for adapter, I tried to bleach my Nikkor and failed as well. Then Mark_McD at dpreview told me that many modern windows block UV, so bleaching behind the window is ineffective.

I also have to say that the article is not quite clear. First he says that 6 lenses received thorium/lanthanum glass, but does not say which ones. Then he says that a bunch of high quality lenses were calculated with the help of computer and lists them (58/1.2 is in the list). Then he says that 58/1.2 is yellow, but not because of radiation. To me this would indicate that (he thinks that) 58/1.2 does not have thorium/lanthanum glass. However, the pictures he supplies show typical radiation induced yellowing.

Camerapedia http://camerapedia.wikia.com/wiki/Radioactive_lenses classifies it as "contaminated", but quotes no source. Rokkor files http://www.rokkorfiles.com/Lens%20History.html clearly thinks that thorium/lanthanum glass was used, but gives no source. Here's the discussion where the users claim having yellowed and non-yellowed lenses http://www.fredmiranda.com/forum/topic/833131 I haven't found youtube video showing MC 58/1.2 radioactivity.

The most likely conclusion to me is that earlier MC 58/1.2 did have thorium or lanthanum glass and these will yellow. However, manufacturer's stopped using radioactive glass while MC 58/1.2 was still in production, so later copies would not yellow at all. What are the reason behind the claim on artaphot website is unclear. I would just invite him to this discussion.

[Arkku]

I have an MC Rokkor-PG 58mm f/1.2, with the knurled metal focusing ring, and it is radioactive. (Have measured with dosimeter.)