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Thread: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

  1. #1

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    Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    I am just wonder if anyone here was able to completely cleared the yellowing of the Bell and Howell 6 inches f/2.5 or AE 6 inches f/2.5 ?
    I have no problem clearing out AE 7 inches' yellow in 1 day, but I am still trying to wrap up the remaining yellowing of B&H 6''.

    Basically I found out this lens have both thorium on both front and the back groups, unlike the AE7 which has only in the rear group.
    For tool , I used an LED 300 Watts grow light that I already have several years, which has full-spectrum and more UV than regular Ikea LED light .
    It is also convenience because I can mass bleaching several thorium lenses at the same time. I surmise that the bleaching will speed up much with higher wattage , say 600 watts or 1200 watts

    With this particular lens I was able to clear most of the yellowing within 2 days (12 hours per day) , about 90%, but it seems the last 10% is hard to get rid of.
    FYI I am still using the LED light to clear off the remaining as mentioned above.

    I post some pictures for your consideration, and a video as well (that has flickering which showed the pulsating emission) .



    B&H Before Bleaching





    B&H After 2 Days of Bleaching







    Flickering video of the bleaching currently


  2. #2

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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    Trippy video, man! Seriously, it seems like you're on the right path. I'd just keep on; there's no exact prescription for the treatment you're trying.

  3. #3

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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    I'd say continue also. I have 2 or 3 of these, and have partially bleached one but haven't gotten to the others. I did fully disassemble them (8 elements I believe), so maybe doing so would help more too.

    Have you shot with them at all? I haven't gotten around to shooting with mine but hopefully will someday.

    -Ed

  4. #4

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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    I am putting another 12 hours and the yellow is still there. It is driving me crazy. I will probably put up with it for another 12 hours.
    I think it is starting to follow this curve


  5. #5

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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    Quote Originally Posted by renditiont View Post
    I am putting another 12 hours and the yellow is still there. It is driving me crazy. I will probably put up with it for another 12 hours.
    I think it is starting to follow this curve

    Hmm. How did you measure the bleaching percentage?

  6. #6

    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    Just think of it as saving you the cost of a K2 filter for B&W.

  7. #7

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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    Quote Originally Posted by Pfsor View Post
    Hmm. How did you measure the bleaching percentage?
    no i am just eyeballin' the percentage the yellow is not that visible if I look through the lens, but if I put it against a white paper it is still there.

  8. #8

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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    Quote Originally Posted by Chauncey Walden View Post
    Just think of it as saving you the cost of a K2 filter for B&W.
    I definitely do not want to pursue this bleaching for long. Probably another 12 hours before I give up .

  9. #9
    Corran's Avatar
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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    I have one of these that for a year was at a local machinist while he tried to figure out a good way of attaching it to a Pacemaker board. He never got around to it. I took it home and put it facing in to a UV light, where it sat for months. It never fully cleared, but it got better. My guess is that it won't clear fully.
    Bryan | Blog | YouTube | Instagram
    All comments and thoughtful critique welcome

  10. #10

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    Re: Bell and Howell 6 inches f/2.5 yellow bleaching using LED Grow Light 300 watts

    Quote Originally Posted by Corran View Post
    I have one of these that for a year was at a local machinist while he tried to figure out a good way of attaching it to a Pacemaker board. He never got around to it. I took it home and put it facing in to a UV light, where it sat for months. It never fully cleared, but it got better. My guess is that it won't clear fully.
    Thank you Corran for ...clearing... it up. Guess I will yank my light in a few minutes

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