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Thread: OC filters in our future?

  1. #21
    Jac@stafford.net's Avatar
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    Re: OC filters in our future?

    Quote Originally Posted by Eric Woodbury View Post
    Sodium vapor will fog paper.
    You have had some bad luck, Eric.

    My Thomas lights do not fog. They each have two sets of filters one of which slightly changes the color of light, and they have doors to lower light intensity more if necessary. (I got new filters a few years ago. The first filters lasted almost thirty years.)

  2. #22
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: OC filters in our future?

    Quote Originally Posted by Eric Woodbury View Post
    Sodium vapor will fog paper.
    Sorry, Eric, but...

    Not true in my tests.

    I left a piece of paper, partially covered, on the counter for an entire printing session (several hours).

    As the last activity of that session, I developed that sheet of paper.
    I could not identify the area that was covered.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  3. #23
    Eric Woodbury
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    Re: OC filters in our future?

    I don't wish to hijack this topic, but to scratch other's itch, no, I have not owned a Na vapor lamp. I have two good friends that have tested them: one the late-great Al Weber and two a colleague of his. Both did threshold testing and found fog. Furthermore, check the spectra of either low pressure or high pressure sodium and find lines in the blue and green areas, albeit not large, but present.

    The point of this link is OC filters in our future. I don't think there is any reason for filtering tungsten black body radiation with an OC filter for what you can get readily, reliably, and lower power from either an amber or red LED.

    If you have success with Na vapor, then this doesn't apply to you. If somebody wants a good safelight for $5 or less, use LEDs.
    my picture blog
    ejwoodbury.blogspot.com

  4. #24
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: OC filters in our future?

    Quote Originally Posted by Eric Woodbury View Post
    I have two good friends that have tested them: one the late-great Al Weber and two a colleague of his. Both did threshold testing and found fog. Furthermore, check the spectra of either low pressure or high pressure sodium and find lines in the blue and green areas, albeit not large, but present.
    There's an old saying: "Ye shall find what ye seek."
    That applies to almost any quest.

    What your friends obviously missed is that the Thomas Duplex safelight is equipped with filters to eliminate that extraneous energy.

    Apples and cumquats.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  5. #25

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    Re: OC filters in our future?

    Quote Originally Posted by Leigh View Post
    192.168.x.x is a non-routable IP address block.

    It cannot be accessed by anyone outside of its own physical domain, like over the internet.

    I tried it and got:
    Non-authoritative answer:
    Name: subclub.org
    Address: 69.49.101.19


    I tried that IP address and it failed.
    It also fails a PING, so it is not accessible over the internet.

    However, when I accessed subclub.org, it worked.

    - Leigh
    192.168.0.1 is my router. I don't understand how it can work if it can't be resolved by ping, nslookup or traceroute. What do you have in /etc/resolv.conf ?
    Last edited by Old_Dick; 14-Dec-2017 at 18:39. Reason: The bleeding obvious.
    Principal Unix System Engineer, Yoyodyne Propulsion Systems

  6. #26
    Jac@stafford.net's Avatar
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    Re: OC filters in our future?

    Quote Originally Posted by Eric Woodbury View Post
    [...] I have not owned a Na vapor lamp. [...] I have two good friends that have tested [...] and found fog. [...] I don't think there is any reason for filtering tungsten black body radiation [...]
    Bogus in too many ways including hearsay, and how does black body radiation relate to this thread? Impression is not science.

  7. #27
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: OC filters in our future?

    Quote Originally Posted by Jac@stafford.net View Post
    ...how does black body radiation relate to this thread?
    A tungsten lamp is a black body radiator, as opposed to an LED, which is not.

    He's talking about filtering light from a tungsten bulb, using an OC filter.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

  8. #28
    Jac@stafford.net's Avatar
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    Re: OC filters in our future?

    Quote Originally Posted by Leigh View Post
    A tungsten lamp is a black body radiator, as opposed to an LED, which is not.

    He's talking about filtering light from a tungsten bulb, using an OC filter.

    - Leigh
    If a source can be seen, or it's measured to be more energetic than ambient radiation (light), it is not a black body.
    .

  9. #29
    Drew Wiley
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    Re: OC filters in our future?

    Beehives and the full range of filters are still easy to acquire; and the relevant specifications for each type of filter is still accessible info. Since I do a lot of color work, I'm accustomed to navigating in total darkness. Even my beehive for b&w paper Dev is on a momentary-contact footswitch. I never leave the safelight on. There is no silver bullet. When in doubt, test first.

  10. #30
    8x10, 5x7, 4x5, et al Leigh's Avatar
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    Re: OC filters in our future?

    Quote Originally Posted by Jac@stafford.net View Post
    If a source can be seen, or it's measured to be more energetic than ambient radiation (light), it is not a black body.
    You obviously do NOT understand the concept of a "black body radiator".

    Look it up.

    - Leigh
    If you believe you can, or you believe you can't... you're right.

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