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Author Topic: Color Blind  (Read 2543 times)

Offline Ben6789

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Color Blind
« on: 04/05/2007 14:58:07 »
Okay, say your color blind to blue. You see a violet car, do you only see the red used to make the violet, or do you see violet?  ???

« Last Edit: 07/05/2007 16:40:28 by Ben6789 »


 

another_someone

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Color Blind
« Reply #1 on: 04/05/2007 22:27:35 »
If you are colour blind to blue, then what colours do you see?

If the only colour you see is red, then it will look monochrome (i.e. you will only see shades of brightness within the red colour frequency, and will not be able to discriminate between that and any other colour, so they will all look grey - rather like a monochrome photograph with a red filter on).

If you can see colours in the red and green part of the spectrum, then the question is whether blue will be totally invisible to you (as ultraviolet is to us), or whether blue will trigger some week response in the green receptors.

Furthermore, violet is not necessarily made up of red and blue.  We detect violet as being a combination of red and blue, and RCG colour displays will diplay violet as a combination of red and blue, but there are many ways of creating a violet display, using lots of different combinations of colours, or even just using a transmission/reflection of a pure colour in the violet part of the spectrum.  It really depends on exactly which combination of spectral lines are used to create the violet colour, and how they match up to the spread of colours that you can perceive, as to what sensation of colour you get.

In any case, what does it mean to say one sees red or blue or violet.  One understands something to be blue insofar s one cannot discriminate between that colour and another thing that is blue.  In reality, there are many ways that one can create the colour blue, and it is just a limitation of our eyes that they all appear as the same colour.  So too, if one can only detect red and green, so all that happens is that we are further restricted in our ability to distinguish different colours, so that colours that we think to be different colours today would seem like the same colour because we lack this additional receptor to make the additional discrimination.  If we we had a 4th colour receptor in our eyes (not outside of the present spectrum, but within it - e.g. in the yellow part of the spectrum), we would be able to disseminate between different colours that today we regard as being one and the same colour, but how would we label these colours is another matter, since we have no names for that which we cannot today perceive.
 

Offline Batroost

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« Reply #2 on: 05/05/2007 11:59:45 »
I listened to a documentary the other day that described how our native language affects the separation of colours we see. Apparently (if I remember it aright) many of the earth's languages do not distinguish between blue and green. One is simply considered to be a darker version of the other. Subjects who speak these languages do not naturally distinguish between these colours even when taught new languages. In other words they do not percieve a difference in colour.

The other oddity I remember is that English is supposed to be unusual in having words for blue/red mixtures (e.g. violet) but not for yellow/green mixtures.
 

another_someone

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« Reply #3 on: 05/05/2007 13:43:31 »
I don't think it is blue and green, but blue and yellow (and gold).

According to Chambers dictionary of Etymology, the English 'blue' has a root that is possibly cognate with the Latin 'flavus' meaning 'yellow', and may be related to the Greek word 'phalós' meaning white.

To quote from the dictionary (referring to the colour blue):
Quote
The name of one colour has often shifted to another colour in the various Indo-European languages so that different colours (here yellow, white, pale or livid) have related forms from the same base.

Green, being the colour of grass and foliage and fresh growth of vegetation, was always the colour of paramount importance in the environment, and has remained far more conserved over time.

 

Offline eric l

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« Reply #4 on: 06/05/2007 18:48:12 »
Colour and colour perception is a difficult matter.  It involves physics, chemistry, physiology, psychology - and apparently linguistics, too.

  • PHYSICS :  visible light is limited to wavelengths from 380 to 780 nm.  Each wavelength gives a specific colour.  But that is not true the other way around, it is not so that every colour we can see is created by one specific wavelength.  Light of one specific wavelength is called "monochromatic", we find it in lasers, in the lab, and occasionally in fireworks (or something very close to it).  If you see a violet car, you see reflected light, part of which has been absorbed by the pigments in the paint.  If you analyse this reflected light (luminosity in function of wavelength), you will find a curve with a number of peaks.  At which wavelength you will find a peak is a matter of chemistry
  • CHEMISTRY :  it is the chemical structure that will determine the wavelength of an absorption peak because light energy is used to make electrons in a molecule jump from a low energy level to a higher energy level.  Each possible jump requires a specific amount of energy, that comes from a photon at a specific wavelength.  In chemistry, such absorption peaks - mainly in the IR band - for the determination of the chemical structure of a molecule.
    But to create a desired colour, we mix different pigments.  An most colours can be created by different combinations of pigments (for the same colour).  How that is possible is a matter of physiology.
  • PHYSIOLOGY :  to see a colour, the eye does not make a spectral analysis.  The eye has two types of sensors :  the rods and the cones.  The rods are easy :  they give a signal proportional to the intensity of the light, and with the rods only you would have something like a black and white photograph.  For seeing the colour, we need the cones.  We have three types of cones, each with a different sensitivity graph when you set out sensitivity in function of wavelength.  The peak sensitivities are respectively with red, green and blue.  That is why computer an televisions screens work with the famous RGB system :  the ratio of the three components (red, green and blue) determines the colour of the pixel.  But keep in mind that each type of cones gives a signal at any visible wavelength, only the signal for the same amount of energy received varies with the wavelength.
    If you say that you are colour blind for blue, I suppose that you lack the cones that are most sensitive to blue.  But even monochromatic blue will give some signal (though a weak one) with the cones that are most sensitive to green, or those that are most sensitive to red.
    Any colour we see is the result of three signals by three types of cones, it is the ratio between the three that determines the colour.
    There are more than three pigments, there are dozens of them.  And every pigment gives a specific response with each of the three types of sensors.  This means that different combination can add up to the same result.
    One of the weird things with your colour blindness is that it may be possible that you see a difference between two violet cars (of different makes, using different combinations of pigments) where a "normal" person would see no difference, because you lack the blue-sensitive cones (which makes the other types more important).  But what name you will give to these colour perceptions is a matter of psychology. 
  • PSYCHOLOGY :  Let us not forget that everyone has always called the colour you see for that car "violet", so however you perceive this colour, you are bound to call it violet !  Your colour blindness is noticed only when you can not make a distincition between two shades, or when you see a distinction where nobody else does, or when you are asked to place place your violet on a scale between red and blue, and give a rating that is different from that of everyone else.

Now, apparently, there is also a question of linguistics or etymology, but I better leave that out.

 

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Color Blind
« Reply #4 on: 06/05/2007 18:48:12 »

 

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