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Colour: you heard it on Horizon

  1. Aug 12, 2011 #1

    sophiecentaur

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    At last someone has made a point of broadcasting that colour is in your head and not wavelength. The recent BBC Horizon programme on TV, whilst being a bit fanciful and touchy feely, made it quite clear that the colour we see / appreciate is affected by many factors and totally depends on the individual and on how that individual happens to be feeling, how he has been brought brought up and what the present / recent lighting conditions happen to have been.
    Good 'ol BBC.
     
  2. jcsd
  3. Aug 12, 2011 #2

    Claude Bile

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    Nonetheless, we all still agree what is 'red' and what is 'green' for example which is the important thing (and just as well, at least when it comes to driving).

    Claude.
     
  4. Aug 12, 2011 #3
    wow!
     
  5. Aug 12, 2011 #4
    Sure everyone could see the color blue as a different color and all agree that they are seeing blue, but they know it is blue because that wavelength sends a different signal than any other color. Some people even feel colors, or taste them. There are chemicals you can take that can allow a normal person to feel or taste or hear colors. Your just taking that familiar signal and crossing it to inappropriate areas of the mind.

    However the fact that each wavelength activates specific cones in our eyes and the color that we all agree on is discrete means that color is wavelength.
     
  6. Aug 12, 2011 #5

    sophiecentaur

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    And it's no surprise that we choose two extremes of colour for those purposes. (You can neglect blue because it's a low luminance colour and would not be easily visible in many circumstances). You'd never go for scarlet and crimson as your two traffic light colours, for instance.
     
  7. Aug 12, 2011 #6

    sophiecentaur

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    @ LostConjugate
    I had an email notifying me of a post but the post doesn't show on this forum. Your description of colour vision is totally flawed (and you are not alone in this). This is why I started the thread and referred people to the Horizon Prog. Blue is NOT "a specific wavelength" and it is not because
    " each wavelength activates specific cones in our eyes and the color that we all agree on is discrete means that color is wavelength".
    Can you not understand that, whilst a particular wavelength 'looks' a particular colour, most (in fact, pretty much all) colours we see are due to a whole mixture of wavelengths. Colour TV would never work if our eyes worked the way you are implying.
    There is no TV display in the world that only produces a single wavelength of light when displaying ANY colour. Display phosphors are just not like that. Read some facts about the system before you start to hold forth on it.
    Edit - I now see your post and my comments still stand.
     
  8. Aug 12, 2011 #7
    Cones in the eyes are tiny resonators, just like in a radio they are tuned to a specific station. Sure it resonates within a range of wavelengths/freq but that range is what defines the color.
     
  9. Aug 12, 2011 #8

    sophiecentaur

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    SO ......... all the colours seen by the 'blue' receptors are seen as 'blue' are they? How does that account for the fact that 1. The receptors that you call 'blue' receptors have sensitivity extending pretty much over the whole visible range (and likewise for the other two receptors)?
    and 2. If these things you call "resonators" have a bandwidth of a large chunk of an octave - not a very tight resonance, is it? That would be like having your VHF radio receiver picking up every VHF radio station on the dial at the same time. The analogy is not a good one. The cones do not have any idea about the specific wavelength they are picking up, you know. It is the combination (mix) of the three sensor outputs that gives us the sensation of colour.

    Can you suggest a single coloured thing that you have seen, recently, from which the light entering your eye was monochromatic?
     
  10. Aug 12, 2011 #9
    http://wiki.umd.edu/wikivision/images/9/9d/Color_1.jpg

    This is a good image that shows how our cone/rod receptors in our eyes respond to different wavelengths.

    I never thought I would have to crack open my first year Psych textbook again but here's the blurb in it about cone/rods:

    "The Triochromatic Theory states that color vision emerges from the combined activity of three different types of receptors, each most sensitive to a different range of wavelengths. ... It would be possible to match any visible color by varying the relative intensities of three primary lights, each ov which acts maximally on a different type of receptor. ... Three types of cones indeed exist in the humin retina, each with a different photochemical that makes it most sensitive to light within a particular band of wavelengths
    ...
    The cones are labeled "blue," "green," and "red," after the color that is experience when that type of cone is much more active than the other types. Notice that any givene wavelength of light produces a unique ratio of activity in the three types of cones. For example, a 550-nm light, which is seen as greenish-yellow, produces a slightly larger response in "red" cones than in "green" cones and a very low response in "blue cones". *see the pictures I posted* That same ratio of response in the three cone types could be produced by shining into the eye a mixture of red, green, and blue primaries, with the first two much more intense than the last. The result would be a perceptual experience of greenish-yellow indistiguishable from that produced by the 550-nm light"
    -Psychology - Fifth Edition. Peter Gray.
     
    Last edited by a moderator: Apr 26, 2017
  11. Aug 12, 2011 #10
    Yes but they "resonate" at a more specific range.

    I agree with everything your saying here, but I don't understand how it leads to color not being the result of wavelength. I am pretty sure last time I played around with a monochromatic laser it looked green, and yup, I looked directly into it (bad).

    It sounds like we are not on the same wavelength here.
     
  12. Aug 12, 2011 #11

    sophiecentaur

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    Response to the Phych Textbook passage:
    That's all perfectly right EXCEPT for the bit about the indistinguishablilty of the spectral yellow and the synthesised yellow. The resultant of a red and a green primary does not actually lie on the same part of the chromaticity diagram as the spectral yellow. It can be made to lie on the same radius(chrominance phase) from the centre (white) but lies on a chord, joining the two primary primary points and not on the spectral curve. Near enough but not the same. (Also, you would just NOT want to be adding any blue - that would just desaturate the synthetic yellow even more)
     
    Last edited: Aug 12, 2011
  13. Aug 12, 2011 #12

    sophiecentaur

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    Colour, of course, depends upon the light entering the eye. BUT, it is (99.99% of the time) due to a combination of light of different wavelengths. Furthermore, you can produce the SAME colour sensation with many different combinations of contributing wavelengths and intensities. I am just arguing against saying that colour is wavelength - it definitely isn't, because saying 'wavelength' with no further qualification, implies just one wavelength. As I said, above, you never get just one wavelength.

    I guess the nearest equivalent would be to say that the chord of Cmajor just consists of one frequency. Yes- there will be some 440Hz in there but what about the frequencies corresponding to the Third, Fifth etc?? And there's Cminor, Cdiminished, C augmented etc etc. Very analogous to colours, don't you think?

    Bad boy looking into a laser. But where were the lasers when our colour vision evolved?
     
  14. Aug 12, 2011 #13
    Well this is the idea behind resonance. Frequency is fundamentally uncertain anyways.

    Does it mean that to tune your radio to 104.5 is incorrect. That the station should not be defined by its frequency?
    Is it 104.50000000000000000000000000000000000000000000000000000000 or is it 104.50000000000000000000000000000000000000000000000000000007?

    The ranges of frequency we are talking about are relatively small ranges in the entire spectrum.
     
  15. Aug 12, 2011 #14

    DaveC426913

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    No, it's more comparable to a station that broadcasts at 101.5, 103.5, 105.5 and 107.5. Does it make sense to say that radio's frequency is 104.5? 104.5 is actually silent.

    Like he said, optically, the real world is not made of single frequencies.
     
  16. Aug 12, 2011 #15

    sophiecentaur

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    The range is the equivalent to the whole of the fm broadcast channel, as a fraction of the band centre. Also, where did you read that apart from the basic quantum idea, there is a resonance in the colour receptors? Would it not just be a general broad-band absorption? But, anyway, how is all this relevant to what I see as your basic mis-conception?
     
  17. Aug 12, 2011 #16
    http://en.wikipedia.org/wiki/Cone_cell

    All senses are a resonance phenomenon. Trying not to get too philosophical but I must say consciousness is a resonance phenomenon.
     
  18. Aug 12, 2011 #17

    sophiecentaur

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    You mean the same as crystals help you focus your energy on the workings of your body? I thought this was a Physics forum.
     
  19. Aug 12, 2011 #18
    No I don't think I meant that.

    I mean that sound is a resonance phenomenon, thought is a resonance phenomenon, touch, taste, etc.
     
  20. Aug 12, 2011 #19

    sophiecentaur

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    You would have to define what you mean by "resonance" in your description. It seems to have little to do with the response of a system with a natural frequency of oscillation to a periodic disturbance - which is the normally understood meaning. Whilst it is true that the hairs in the cochlea do resonate at appropriate frequencies, what is in smell or touch that is frequency related or narrow band? This is far too fanciful if you want to have a serious discussion about colour and the way that the photochemical receptors operate.
     
  21. Aug 12, 2011 #20
    I simply mean reaching a much higher amplitude for a certain frequency range enough to be noticed. The cones send a much stronger electric signal when they are subject to a specific frequency range, this signal is picked up by the brain.
     
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