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Thread: Benham disks

  1. #1
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    Benham disks

    How do these things work? I mean, I know how to work them (spin fast) but why do black and white patterns look so colorful? Did not quite understand Wikipedia's explanation.

  2. #2
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    Thye're called Fechner Colours, which is a useful search term.
    Short wavelength retinal cone cells respond more slowly than long wavelength cones, so if you present the retina with rapidly flickering white light, you produce mismatched colour signals from the retina that don't properly balance out to a neurological white signal.
    How that mechanism plays out in detail still seems to be a matter for debate (128KB pdf).

    Grant Hutchison
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  3. #3
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    I wonder if this might be related to the effect which causes visual problems (flickering color bands along high-contrast sharp edges) for some people when DLP video projectors are used. Some people (like me) have to concentrate to even notice the projector effect. Others are made nauseous by it.
    Selden

  4. #4
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    Are the colors universal or idiosyncratic? If I see blue in one line, will someone else see red-violet, and another person lime green?

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    Quote Originally Posted by Tom Mazanec View Post
    Are the colors universal or idiosyncratic? If I see blue in one line, will someone else see red-violet, and another person lime green?
    Not perfectly universal, because we don't all match particular Fechner colours to the same colour chip, but not entirely idiosyncratic either, since the effect relies on underlying chemistry and physiology we largely all share.
    There's also quite a lot of within-individual variation according to things like ambient lighting, attention, fatigue ...

    Back in the 1960s the BBC's science strand Tomorrow's World made a brief colour broadcast on black and white TVs, using Fechner colours. (This was before anyone worried about flicker-induced epileptic fits.) I remember a woman's lips, supposedly wearing bright red lipstick, which I saw as a deep muddy brown. Discussion the next day suggested that a lot of people saw the intended red, but many saw a shade of brown (caused by an admixture of a green sensation). But that was the range of experience, IIRC - there were no bright blues or purples, which makes sense in terms of a largely shared physiological response.

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

  6. #6
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    Here is a report of widely varying colors: http://www.dailymail.co.uk/sciencete...knows-why.html
    SHARKS (crossed out) MONGEESE (sic) WITH FRICKIN' LASER BEAMS ATTACHED TO THEIR HEADS

  7. #7
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    Quote Originally Posted by Tom Mazanec View Post
    Here is a report of widely varying colors: http://www.dailymail.co.uk/sciencete...knows-why.html
    The Daily Mail?
    You can achieve a reasonable understanding of the world by believing exactly the opposite of anything the Daily Mail tells you.

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

  8. #8
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    Quote Originally Posted by grant hutchison View Post
    The Daily Mail?
    You can achieve a reasonable understanding of the world by believing exactly the opposite of anything the Daily Mail tells you.

    Grant Hutchison
    I've always wanted to ask the British members of the board which of the online British news sources were "real" and which were Europe's version of the National Enquirer.

    American sourced news outlets can be so predictably tedious.
    Time wasted having fun is not time wasted - Lennon
    (John, not the other one.)

  9. #9
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    Quote Originally Posted by BigDon View Post
    I've always wanted to ask the British members of the board which of the online British news sources were "real" and which were Europe's version of the National Enquirer.

    American sourced news outlets can be so predictably tedious.
    oh lament, the sad decline of journalism. Online BBC is in my view still the best but they have erred toward small bites and away from in depth stuff. The papers are partisan mostly , the Guardian is left wing, the Telegraph is right wing and getting worse I fear, the Times has lost a lot of journalists, the Financial Times is still good for general news IMO. The Daily Mail has sunk so low, it's a right wing one. The press make a fair complaint that the licence fee funded BBC has an unfair advantage but I would not change that personally. I prefer radio BBC (and radio NPR too) You can get that online for example search "bbc radio 4" and also the bbc podcasts. I am sure I am biassed but I use BBC for news.
    sicut vis videre esto
    When we realize that patterns don't exist in the universe, they are a template that we hold to the universe to make sense of it, it all makes a lot more sense.
    Originally Posted by Ken G

  10. #10
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    Anything with "Daily" on its masthead on weekdays should be used for entertainment purposes only: Daily Star, Daily Mail, Daily Express, Daily Mirror. The Sun falls into the same category.
    There's quite a good article about British newspapers, for the guidance of foreign students visiting the UK, here.

    Grant Hutchison
    Blog

    Note:
    During life, we all develop attitudes and strategies to make our interactions with others more pleasant and useful. If I mention mine here, those comments can apply only to myself, my experiences and my situation. Such remarks cannot and should not be construed as dismissing, denigrating, devaluing or criticizing any different attitudes and strategies that other people have evolved as a result of their different situation and different experiences.

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