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  1. #1

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    M42 50mm SMC Takumar f/1.4 Yellowed - Light Source Suggestions?

    Hi,

    I have a yellowed SMC Takumar in M42 for my Spotmatic. I love the lens for b/w, but I want to shoot color with it and I find the yellowing drops probably a full half-stop from getting through the viewfinder (which at my age is increasingly a problem).

    I could just set it out in the sun as such: http://www.apug.org/forums/archive/i...p/t-41848.html

    But, is there a better/faster way to get UV on it?

    Thanks,

    Clint

  2. #2
    Steve Smith's Avatar
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    I can't think of a bigger or brighter UV source.


    Steve.

  3. #3
    Chrismat's Avatar
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    I've read blogs where people have used a black light. They put the black light and the lens in a shoebox. I used the sun method myself for my Takumar 1.4, but make sure you wrap the lens body in aluminum foil. If not, the black exterior of the lens is going to absorb a lot of heat possibly loosening the lens elements.

    Chris

  4. #4

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    With the yellowing of the lens element what you will see will be a slight warming of colors. People will tolerate any color shift provided it is toward a warm color. I would try the lens with at least one roll of color slide film and determine whether you like the colors. Putting the lens in the sun can cause lubricants to migrate to the lens elements. Once this happens the lens must be disassembled and cleaned.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

  5. #5
    brucemuir's Avatar
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    Dont feel bad Zen…I have a 35 1.4 Nikkor in the same condition. The only part that bugs me is the light loss (that cant be proper grammar)

    I haven't gotten around to trying a fix…the sun is only good during certain seasons around here.

  6. #6
    ignatiu5's Avatar
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    I've used the sun before for M42 Pentax lenses, but I recently wanted to speed up the process for a yellowed SMC Takumar 6x7 lens. I tried the UV lamp in my biosafety cell culture cabinet for hours and hours. I tried the UV of a DNA crosslinker box, again for hours times multiple sessions. Neither was as effective as the window ledge wrapped in aluminum foil. Go figure.

  7. #7

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    I bought a UV-A reptile light at Petco. Cleared up a yellowed radioactive LTM Summicron 50 in about 10 days.

  8. #8

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    Bruce, its possible to remove the cells from the 35 1.4. I cleared one of mine and kept one yellowed, looks nice in B&W. The one I cleared took at least 2 weeks, all day, but it was in the winter, put the lens on a old busted body and wrapped with foil.

  9. #9
    polyglot's Avatar
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    Sun is the cheapest option; for faster you need a UV lamp bright enough that it's a hazard to humans, e.g. a medical-sterilisation tube.

  10. #10

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    Hello,
    I have cured 2 SMC 1,4/50 Takumars under an OSRAM Vitalux 300 W lamp in a distance of about 20 cm (about 8''). I think this is similar to what is described above as UV-A reptile lamp. It took about 2-3 days. The lens was wrapped in aluminium foil an I put a metal sheet with a roud opening for the rear lens over it, but nevertheless it got about 60° C warm. I neither had lens separation nor problems with migrating lubricant. Not only the UV irradiation but also heat causes the bleaching, but you have to be careful not to to melt the lens cement. Besides the radioactive lens (contains Thorium, an alpha-emitter) is in the rear element (affirmed by a Geiger counter), so put this towards the light source. I put a little mirror under the front lens (without filter!), so the light is reflected and can work two times. I want to warn to do the same with the 1:2/35 mm Takumar since this lens will suffer lens separation in the rear element by the resulting heat (the glas types seem to have different thermal expansion)!
    Some weeks ago I have read that a LED lamp from the international furniture house IKEA (the name was JANSJÖ) was successfully used for this and had success in less than one day! So I assume that every strong LED lamp (MAGLITE; LED lenser; CREE LED) could do the same job without producing so much heat like a UV-A reptile lamp and does not need so much electrical energy, only a set of batteries.

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