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Thread: Light

  1. #1 Light 
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    i understand colour does not exist without light but can light exist without colour (as i know colour makes up part of the suns frequences)

    Thanks Rachel (Art student)


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    Brassica oleracea Strange's Avatar
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    It probably depends what you mean by "colour". Would you consider white light (i.e. sunlight) to have colour?

    Or what you mean by "light". Infra-red and ultra-violet don't have colour (because we can't see them). But I don't know if they count as light.


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    Color is a perception or interpretation by our brains of wavelength.
    Our brain can only perceive a limited amount of EM radiation directly.
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    Quote Originally Posted by rachelshrive View Post
    i understand colour does not exist without light but can light exist without colour (as i know colour makes up part of the suns frequencies)

    Thanks Rachel (Art student)
    Yes it can, the human eyes contain both rods and cones, in some rare cases the cones do not function as intended and without working cones there is only black and white vision. Not sure what that would be like and it would be very tough trying to explain color to this individual. But if you were born that way it would be normal for you, at least until they wouldn't give you a drivers license.

    There are animals that do see in infrared and ultraviolet.

    Birds, unlike humans but like fish, amphibians and reptiles, have four types of colour receptors in the eye. These give birds the ability to perceive not only the visible range but also the ultraviolet part of the spectrum, and other adaptations allow for the detection of polarized light or magnetic fields. Birds have proportionally more light receptors in the retina than mammals, and more nerve connections between the photoreceptors and the brain.
    The retina is a relatively smooth curved multi-layered structure containing the photosensitive rod and cone cells with the associated neurons and blood vessels. The density of the photoreceptors is critical in determining the maximum attainable visual acuity. Humans have about 200,000 receptors per mm2, but the House Sparrow has 400,000 and the Common Buzzard 1,000,000. The photoreceptors are not all individually connected to the optic nerve, and the ratio of nerve ganglia to receptors is important in determining resolution. This is very high for birds; the White Wagtail has 100,000 ganglion cells to 120,000 photoreceptors.

    Rods are more sensitive to light, but give no colour information, whereas the less sensitive cones enable colour vision. In diurnal birds, 80% of the receptors may be cones (90% in some swifts) whereas nocturnal owls have almost all rods. As with other vertebrates except placental mammals, some of the cones may be double structures. These can amount to 50% of all cones in some species.
    Many animals have a tissue layer called the tapetum lucidum in the back of the eye that reflects light back through the retina, increasing the amount of light available for it to capture. This is found in many nocturnal animals and some deep sea animals, and is the cause of eyeshine. Humans lack a tapetum lucidum.
    I couldn't find very many animals that can see infrared, one of the problems with seeing infrared is that just about everything radiates in infrared and it would interfere with our normal vision. However I believe many snakes, especially vipers have infrared receptors, but then they already have poor regular vision.

    Hope that helped a bit.
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    Pit vipers.
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    Bees see in the ultraviolet. They can't see orange, yellow or green, but can see a narrow range of blue-green.

    Interesting.

    Vision of a human compared to vision of bee
    Its the way nature is!
    If you dont like it, go somewhere else....
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    Here's a page of various color blindness test charts. If you open up a test and have trouble seeing the number or image, it means you have some degree of color blindness.

    color blindness test - Bing Images







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    Alec Bing must think you're great. You're always drawing attention to her screen name.
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  10. #9  
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    Here's one I'm having trouble with. I can't tell what it is for the life of me.

    color blindness test - Bing Images
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  11. #10  
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    Another Bing image EM spectrum chart

    em spectrum chart - Bing Images
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  12. #11  
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    I like this chart but you can barely see the visible light range.

    em spectrum chart - Bing Images
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  13. #12  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by Bad Robot View Post
    Yes it can, the human eyes contain both rods and cones, in some rare cases the cones do not function as intended and without working cones there is only black and white vision.
    Ah! This might be most relevant to the original question: because the cones are less sensitive, in low light levels we only see in black and white. Light with no colour!
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  14. #13  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by Bad Robot View Post
    Here's one I'm having trouble with. I can't tell what it is for the life of me.

    color blindness test - Bing Images
    It could be a problem with the colour gamut of your display...
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  15. #14  
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by Bad Robot View Post
    Here's one I'm having trouble with. I can't tell what it is for the life of me.

    color blindness test - Bing Images
    It could be a problem with the colour gamut of your display...
    Yes, it could be a possibility. You didn't state whether you could make out the image on your monitor or not. Plus most of the other images I could easily make out the image for different color combinations. I am assuming they put those test together to measure known color blindness issues.

    I also remember reading somewhere that most people do have some mild color perception issues which are not concidered a problem, because they don't ever put your life in danger such as a red, green color blindness might.
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  16. #15  
    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by Bad Robot View Post
    Yes, it could be a possibility. You didn't state whether you could make out the image on your monitor or not.
    I didn't, did I. But I can't. I wasn't sure if it was a problem with my screen as well. However, looking at the other images in that (rather random) collection, I wonder if that has been cropped from a larger image and so the detail that would make it recognisable is missing. Or maybe it is a control image with no meaning. Or ...
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    I can't make it out either. I can see differences, but I can't see a pattern.
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
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  18. #17  
    Brassica oleracea Strange's Avatar
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    Maybe the pattern is only visible to our Lizard Overlords.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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  19. #18  
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    Of all the images on Bing, that's the only one I can't make out a pattern.
    Its the way nature is!
    If you dont like it, go somewhere else....
    To another universe, where the rules are simpler
    Philosophically more pleasing, more psychologically easy
    Prof Richard Feynman (1979) .....

    Das ist nicht nur nicht richtig, es ist nicht einmal falsch!"
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  20. #19  
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    Quote Originally Posted by AlexG View Post
    Of all the images on Bing, that's the only one I can't make out a pattern.
    I couldn't make this one out either.

    color blind test - Bing Images
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