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Thread: Does black exist?

  1. #31
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    Quote Originally Posted by parallaxicality View Post
    Really? That's fascinating. I'd ask for elaboration but I don't think that would be possible.
    Sure it is. I've experienced visual field defects at both the retinal and the cortical level over the years.
    A missing chunk of near-central vision is surprisingly difficult to detect, since the brain simply generalizes the surroundings so as to fill the defect. So I was completely unaware of the missing area of vision and asked a companion, "Where did Declan go to?" when Declan was in fact standing directly ahead of me and waving. For me, he didn't come into view until I got close enough for his visual image to expand into functional areas of my visual field. And looking at a menu written on a whiteboard gave me the impression that someone had wiped away part of the writing, rendering it smeary and indistinct.
    A defect at the edge of vision is even harder to detect, because peripheral vision has so little detail anyway - people can lose whole chunks of peripheral vision without noticing, if it happens slowly. In my case I'd had a retinal bleed that caused a dense black floater tethered in my peripheral vision - and when I stopped being able to see that, I realized my retina had stopped working in that area. But it was only because I had a "reference object" that stayed relatively fixed in my visual field that I was able to detect the change.
    Having a newly and completely blind eye is definitely noticeable, but again there's no sensation of "blackness" - just a sense that something is rather bothersomely missing on one side of your visual field, as well as a sense of disorientation from the sudden loss of 3D vision. It's odd to blink the blind eye and so no change - certainly no "blackness" associated with closing the eye.

    Grant Hutchison

  2. #32
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    Quote Originally Posted by Hornblower View Post
    I can elaborate on it. I have a blind spot on each retina, as we all do. The visual cortex never gets signals from those spots and is programmed to ignore them, so we do not see black spots when looking at a bright field. If a small black spot in the field is projected onto a blind spot, it disappears but the sensation is just whatever surrounding light is present.
    And, of course, with normal binocular vision the blind spots in each eye are not an issue, because there is data from the other eye to fill the gap - so there is no defect in the visual field unless you close one eye.
    (My episodes of near-central vision loss have been cortical, so they were present with both eyes open.)

    Grant Hutchison

  3. #33
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    Quote Originally Posted by Ken G View Post
    At this point, many who don't understand language at all will object "but that's just semantics"
    I hate that as an argument because of course it's semantics; it depends on what you mean by "black", "exist", etc.

  4. #34
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    By the way, as far as your brain is concerned, a lack of retinal illumination is data. There are specific cells, called off bipolar cells, that fire when their little patch of retinal territory is in darkness.

    Grant Hutchison

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    Quote Originally Posted by grant hutchison View Post
    And, of course, with normal binocular vision the blind spots in each eye are not an issue, because there is data from the other eye to fill the gap - so there is no defect in the visual field unless you close one eye.
    (My episodes of near-central vision loss have been cortical, so they were present with both eyes open.)

    Grant Hutchison
    Addendum to my post: I was considering the sensation with one eye closed or covered.

  6. #36
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    Quote Originally Posted by grant hutchison View Post
    By the way, as far as your brain is concerned, a lack of retinal illumination is data. There are specific cells, called off bipolar cells, that fire when their little patch of retinal territory is in darkness.
    How do you know that lack of retinal illumination is data and that it exists .. as far as the attached brain is concerned?

  7. #37
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    Quote Originally Posted by Selfsim View Post
    How do you know that lack of retinal illumination is data and that it exists .. as far as the attached brain is concerned?
    Because there are retinal neurons that fire to indicate the "presence of darkness", and their signals travel up the optic nerve to the visual cortex, where we can see specific V1 neurons firing in response to darkness, which in turn drives the component of dark adaptation that occurs at a cortical level.

    ETA: See Vladusich et al. (2007) for more on the evidence that "darkness" has its own visual pathway, independent of "brightness".

    Grant Hutchison
    Last edited by grant hutchison; 2019-Sep-22 at 09:46 PM.

  8. #38
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    Quote Originally Posted by grant hutchison View Post
    Because there are retinal neurons that fire to indicate the "presence of darkness", and their signals travel up the optic nerve to the visual cortex, where we can see specific V1 neurons firing in response to darkness, which in turn drives the component of dark adaptation that occurs at a cortical level.
    Well, ok .. that's a testable model capable of producing evidence supporting the association of neuron firings with our sense of 'darkness'.
    But that model doesn't produce evidence of the existence of 'darkness itself', though, eh? .. Or does it?

  9. #39
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    Quote Originally Posted by Selfsim View Post
    Well, ok .. that's a testable model capable of producing evidence supporting the association of neuron firings with our sense of 'darkness'.
    But that model doesn't produce evidence of the existence of 'darkness itself', though, eh? .. Or does it?
    I don't know what you mean by "darkness itself".
    I was responding to the OP suggestion that "black" was simply the result of our brains crying "insufficient data". Our brains receive lots of information about which areas of the retina are unilluminated, so the quale "black" is produced in response to data, not to a lack of data. See the link I edited into my previous post for more on that topic. Whereas insufficient data produces the odd visual perceptions I described earlier, in relation to my own experience of visual field defects.

    Grant Hutchison

  10. #40
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    A photon detector or an eye detects a level of impinging light that can be quantified.

    Zero is a quantifiable level. Yes, black exists.


    Followup question:
    Does white exist?

    Unlike having a lower limit, the amount of impinging light has no upper limit. Technically, any collection of equal strengths of all wavelengths is just some high degree of grey.

  11. #41
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    This may be threatening to evolve into a discussion on the meaning of "exist", and could go the way of the Reality Thread.

  12. #42
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    Quote Originally Posted by DaveC426913 View Post
    A photon detector or an eye detects a level of impinging light that can be quantified.

    Zero is a quantifiable level. Yes, black exists.
    Are there places in the universe where there is an absolute lack of visible photons?


    Sent from my iPhone using Tapatalk
    As above, so below

  13. #43
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    Quote Originally Posted by Hornblower View Post
    This may be threatening to evolve into a discussion on the meaning of "exist", and could go the way of the Reality Thread.
    Do you mean the absolute, most stupendously successful thread in the entire history of BA or Cosmoquest .. that thread?


  14. #44
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    Quote Originally Posted by Jens View Post
    Are there places in the universe where there is an absolute lack of visible photons?


    Sent from my iPhone using Tapatalk
    If I am not mistaken, no. Absolute zero would be needed. At 2.7K they will be few and far between compared to the zillions of microwave photons, but there should be a few in the vastness of the universe.

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    Its interesting to note that one of the very foundations of Physics is that information cannot be lost. Loss of information is the same as generating entropy .. which means generating heat. The process of losing all information would disintegrate our universe, (as Physics explains it). Black objects emit radiation. There is information there, (producing the blackness), for us to detect.

    Grant H’s model is of great benefit to science in terms of helping to localise defects in physiology. A loss of neuron firing data, may lead to a diagnosis of where the defect lies. The undiagnosed patient already suspects a defect, otherwise, why else refer to such a model in the context of blackness representing absence?. Either way, the outcome of using such a model is to diagnose defect/no defect.
    Our visual sense relies on distinguishing 'things' (or contrasting them) from a visual landscape (backdrop). If we couldn't perceive contrast, there would be no distinctions between a landscape/backdrop and 'things' .. just some sort of a continuum. 'Things' could not be singled out as existing in such a visual sense only hypothetical model.

    The ’insufficient' data term in the OP, (which I interpret as insufficient information), is a relative term, because there is always information in a universe described by Physics .. and never none.

  16. #46
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    Quote Originally Posted by Hornblower View Post
    If I am not mistaken, no. Absolute zero would be needed. At 2.7K they will be few and far between compared to the zillions of microwave photons, but there should be a few in the vastness of the universe.
    In theory, one could find onesself in the middle of a dense coal sack. While there would be plenty of photons, it's conceivable none of them would be in the 440-770nm range for some arbitrary duration of time.

  17. #47
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    I would say that in Ye Olden times- 'black' exists in the same way that 'red' qualia exists. (pre-scientific/ naive realism)

    That now "Black" exists in the same way a "Hole" exists (scientific= lack of photons interacting with rods in retina)

    Here's a question:

    what is 'blacker" - eyes closed in a dark room, vs vanta black viewed in a bright room.
    I'd say the latter as perception of contrast is what gives true- blackness... and that a totally dark room generates visions (Phosphenes) "on the inside of our eyelids" which we usually ignore.. but will keep you up at night if you notice them.. like tinnitus!

    https://visioneyeinstitute.com.au/ey...ee-close-eyes/
    Last edited by plant; 2019-Sep-23 at 10:32 AM.
    "It's only a model....?" :-)
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  18. #48
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    If we were to define colors by the frequency of light and black as the absence of light then in that context it seems that black would be a condition rather than a color. I think it makes sense to include conditions in the set of things that can exist, at least when they do.

    In the context of visual perception classifying black as a condition makes some sense too. Or perhaps even all perceived colors. The color names are labels to describe a complex set of circumstances (frequencies of light, biochemistry in the eye and visual cortex, experience, more) that together result in a human seeing a certain color.

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    Quote Originally Posted by Darrell View Post
    If we were to define colors by the frequency of light...
    But we don't.

    Mauve and violet might be the same frequency of light, yet they are very different colours. Same with red and pink. Indigo and robin's egg blue.

    And, of course, the obligatory magenta - which is not one frequency of light at all.

    Colour is a consequence of perception.

  20. #50
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    Quote Originally Posted by Darrell View Post
    In the context of visual perception classifying black as a condition makes some sense too. Or perhaps even all perceived colors. The color names are labels to describe a complex set of circumstances (frequencies of light, biochemistry in the eye and visual cortex, experience, more) that together result in a human seeing a certain color.
    It is true that our perception depends on circumstances. I think this is why people specified that you have to be clear what you mean by black. Because if you are going to have paint colors, it doesn't make much sense to say, "the color that is caused by an absence of photons" or "all the frequencies together" or "a color that looks like red when it's bright outside but which becomes a dull grey in very low lighting conditions."
    As above, so below

  21. #51
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    Quote Originally Posted by DaveC426913 View Post
    But we don't.

    Mauve and violet might be the same frequency of light, yet they are very different colours. Same with red and pink. Indigo and robin's egg blue.

    And, of course, the obligatory magenta - which is not one frequency of light at all.

    Colour is a consequence of perception.
    I wasn't stating that we do I was stating a premise. But, I'm not quite sure what you mean. If mauve and violet are the same frequency or same combination of frequencies of light then they are the same color, just different labels. All humans with vision that falls within the normal range for humans will see the same color though they may label it differently.

  22. #52
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    Quote Originally Posted by Darrell View Post
    I wasn't stating that we do I was stating a premise. But, I'm not quite sure what you mean. If mauve and violet are the same frequency or same combination of frequencies of light then they are the same color, just different labels. All humans with vision that falls within the normal range for humans will see the same color though they may label it differently.
    Colour exists beyond the spectral locus, however. I'm not particularly convinced that violet and mauve actually have the same hue, but we also need to consider saturation and lightness, too. It's those properties that give us the difference between browns and yellows or reds and pinks, for instance.

    Grant Hutchison

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    Quote Originally Posted by Darrell View Post
    I wasn't stating that we do I was stating a premise. But, I'm not quite sure what you mean.

    If mauve and violet are the same frequency or same combination of frequencies of light then they are the same color, just different labels. All humans with vision that falls within the normal range for humans will see the same color though they may label it differently.
    Mauve an violet are distinctly different colours, even though they are the same frequency.

    mauve.png

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    Quote Originally Posted by DaveC426913 View Post
    Mauve an violet are distinctly different colours, even though they are the same frequency.

    mauve.png
    Very interesting. Could you explain a bit or point me towards some information on that? From the few minutes I spent looking into it Violet is a spectral color (single wavelength) while Mauve is a shade of purple and is a composite color (a combination of wavelengths).

  25. #55
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    Quote Originally Posted by DaveC426913 View Post
    Mauve an violet are distinctly different colours, even though they are the same frequency.

    mauve.png
    My bold. That is a grossly oversimplified attempt at a description. That mauve is clearly light gray with an admixture of violet, which means a range of frequencies. The saturated violet can be a single frequency, but not in this display. The typical emitters on color monitor screens are not capable of producing spectral violet. At best they imitate it with mixtures of red and blue.

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    Quote Originally Posted by DaveC426913 View Post
    Mauve an violet are distinctly different colours, even though they are the same frequency.

    mauve.png
    This demonstrates the need to understand that visible color isn't just wavelengths but must include intensity of each wavelength as well. I've seen, even astronomers, argue the Sun is white because sunlight has all the colors of the visible spectrum. But they are forgetting that all stars (formal definition) have all the colors. Blue-white stars have all the colors but the intensity of the blue end is far greater than the nearly flat (surprisingly so) photon distribution from the Sun. Are blue stars white?

    Also, though Grant has addressed it, the brain is involved in color determination. Dr. Lamb (Polaroid creator) coined the term retinex to include both the eye and the brain functioning together. As mentioned earlier, a color like yellow (~ 580nm and very narrow in band width) can be monochromatic or can contain wavelengths with no yellow wavelength but the retinex sees it as yellow. These are called metamers. The lighting industry sells some lightbulbs that has us seeing white but they are emitting only a few wavelengths at great intensity.

    Oversimplifying perhaps, but couldn't black just be a value of 0 for all intensities across the visible spectrum?
    Last edited by George; 2019-Sep-24 at 04:03 PM.
    We know time flies, we just can't see its wings.

  27. #57
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    Quote Originally Posted by DaveC426913 View Post
    But we don't.

    Mauve and violet might be the same frequency of light, yet they are very different colours. Same with red and pink. Indigo and robin's egg blue.

    And, of course, the obligatory magenta - which is not one frequency of light at all.

    Colour is a consequence of perception.
    There is no brown in the rainbow.
    "It's only a model....?" :-)
    https://www.youtube.com/watch?v=m3dZl3yfGpc

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    .. not to mention colors that only a tetrachromat can see.

    https://en.wikipedia.org/wiki/Tetrachromacy
    "It's only a model....?" :-)
    https://www.youtube.com/watch?v=m3dZl3yfGpc

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    Quote Originally Posted by plant View Post
    There is no brown in the rainbow.
    Picky but that depends what colour filter you use, a brown transmission filter like a slide of a muddy scene will give you brown or indeed any colour so it must be in the rainbow as white light. Our eyes interpret mixes of frequencies.
    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

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    Quote Originally Posted by plant View Post
    .. not to mention colors that only a tetrachromat can see.

    https://en.wikipedia.org/wiki/Tetrachromacy
    Reading about that took me to this page on "impossible" colours: https://en.wikipedia.org/wiki/Impossible_color

    There are a couple of examples which combine yellow and blue, or red and green, which seem to cause some people to perceive a colour that is neither and which they cannot describe. When I tried it, I saw a square that had alternating waves of the two colours passing over it. Quite odd.

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