Do Nikon use thoriated lens?

Discussion in 'Classic Manual Cameras' started by kl122007, Aug 8, 2009.

  1. There are so many AF stuff are dealing in the Nikon area, but I am here to ask for the non-ai one and regarding to the thorium. I am wishing to know whether Nikon use thorium same as Canon.
    And after having a brief check, it is noticeable that Pentax is thorium-philic for their takumars. Canon also have some thoriated lenses but not in Pentax's amount. So how about Mamiya/sekor and Nikon, how many and which lens is having thorium?
    Thank you, Kevin
  2. Good question Kevin, but I can't help you on this one. Nikon either haven't used Thorium, or are not admitting to it. They do have, of course, all those ED (extra low dispersion) lenses, but I don't know what sort of glass that they use for that.
    Having said that, I have never noticed the tell tale yellowing of thorium elements in any of the old Nikkors that I have. I have a couple of the "hot" Takumars, and the Canon FD 35mm F2, that have yellowed nicely...saves on Y2 filters!
  3. That sounds good for BW photos but not coloured one. I started this post because a reply from my question in FD area said the Nikon 35mm f/1.4 would turn yellow under strong sun light:
    It seems Japanese really enjoy radioactive things to make lens during 70-80s.
  4. Actually, strong sunlight will UN-yellow a thorium element lens. I've de-yellowed a couple of 50mm f1.4 SMC Takumars by leaving them on a windowsill for several days, and it defintely gets rid of the yellow cast.
  5. I have a very yellow first-version 35mm 1.4.
  6. I still have my 35mm F1.4 lens that I bought in the summer of 1978 +/-.
    It is still clear as a bell, for what the info may be worth. I guess it's called Ais today.
  7. Mamiya Sekor optics were not all that great, and didn't really use any revolution technology. I sincerely doubt they would have made a Thorium lens.
  8. Dave,
    it is really a good news for me. I want to remove the yellowing from my FL 58mm. Besides the windowsill method, can I use the small UV lamp which is for money checking?
    I don't really know much about Mamiya. I never use their lenses. And how those m42 lens es makers (excluding Pentax), who is using thorium?
  9. FYI it was not just the Japenese optical industry which used thorium in thier lenses. The Soviet/Russian industry used a great deal of thorium in fast lenses. The 85mm f/2 Jupiter Sonnar copy used it heavily, as did the Industar 61 50mm lens.
  10. I thought the I-61LD used Lanthanum. Either way, I've got a third eye growing out of my forehead. ;-)
  11. Kevin, I have no idea if a UV lamp would work as well as sunlight, because I don't know if it is the UV spectrum or some other part of the spectrum that gets rid of the yellowing. All I know is that sunlight works with the particular glass in a SMC Takumar 50mm f1.4.
    Be sure to rotate the lens, and expose both front and back to the light over the course of several days so that the whole glass gets exposed to the light for a period of time.
  12. Thank you Dave, I will try it out. I need a UV Lamp becuase my living area doesn't have sufficient and strong sunlight (blocked by tall buildings). And I think it would be more favourable to control the UV exposure if I use the UV Lamp.
    I will tell you the result after using the UV Lamp.
  13. oh i didn't know the radioactive glass was called thorium. anyway, i've got a host of nikkors and none of them have ever been yellow but i've got one takumar that has and i've reduced the yellowing by sitting it in a window sill.
  14. There is some radiation test info available on the Web, covering some lenses of different makes, but it doesn't look thorough or exhaustive. Yellowing only occurs in the most extreme cases. Some lenses known to contain thorium oxide in the glass do not emit enough radiation to become yellow, but it's still more than background level radiation.
    Apparently, the use of thorium oxide was abandoned by Japanese SLR lens makers by the mid-1970's.
    Those makes that did use thorium oxide in some products also made others without it. Fast M42 normal lenses by Asahi and Yashica used thorium oxide for a time.
  15. Here are a couple of links, including some older ones from suggesting that early 35/1.4 Nikkors had radioactive elements: (Nikon 35mm f/1.4 Nikkor-N.C Auto non-Ai)
    The big optical glass companies (at least Schott and Hoya) stopped production of glasses with radioactive elements (not only thorium) in the mid 1970s. Some lens manufacturers were thus forced to replace those elements with the newer glass and/or redesign their lenses. There are many more parameters than refractive index, dispersion, partial dispersion (and all their dependence on temperature and other parameters) which make a 1-to-1 replacement of glasses without change in quality nearly impossible.

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