Colour: you heard it on Horizon

[sophiecentaur]

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.

 

[Claude Bile]

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.

 

[jewbinson]

wow!

 

[LostConjugate]

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.

 

[sophiecentaur]

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.

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.

 

[sophiecentaur]

@ 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.

 

[LostConjugate]

@ 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.

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.

 

[sophiecentaur]

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.

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?

 

[Clever-Name]

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.

 

[LostConjugate]

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)?

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.

 

[sophiecentaur]

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)

 

[sophiecentaur]

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.

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?

 

[LostConjugate]

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.

 

[DaveC426913]

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.

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.

 

[sophiecentaur]

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.

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?

 

[LostConjugate]

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?

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.

 

[sophiecentaur]

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.

You mean the same as crystals help you focus your energy on the workings of your body? I thought this was a Physics forum.

 

[LostConjugate]

You mean the same as crystals help you focus your energy on the workings of your body? I thought this was a Physics forum.

No I don't think I meant that.

I mean that sound is a resonance phenomenon, thought is a resonance phenomenon, touch, taste, etc.

 

[sophiecentaur]

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.

 

[LostConjugate]

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.

 

[phinds]

When someone is color-blind, does that mean that their cones don't work right or does it means something happens to the resulting signal that makes the brain not distinguish it in the same way as the brain of someone who recognizes color?

If their cones are flawed, then I don't think my question is relevant to this discussion, but if their cones are OK, but the brain sees black and white doesn't this say something about how "color" is not frequency but a mental interpretation?

 

[DaveC426913]

Bzzt. Point goes to SophieS.

LostC, you're going to have to make a stronger and clearer argument than this. If you're talking about signal strength over a range of frequencies then do so, none of this handwavitudinous "resonance" argument.

 

[LostConjugate]

When someone is color-blind, does that mean that their cones don't work right or does it means something happens to the resulting signal that makes the brain not distinguish it in the same way as the brain of someone who recognizes color?

If their cones are flawed, then I don't think my question is relevant to this discussion, but if their cones are OK, but the brain sees black and white doesn't this say something about how "color" is not frequency but a mental interpretation?

Well yea, we are not saying it is not. Color is a mental interpretation of frequency.

 

[LostConjugate]

Bzzt. Point gores to SophieS.

LostC, you're going to have to make a stronger and clearer argument than this. If you're talking about signal strength over a range of frequencies then do so, none of this handwavitudinous "resonance" argument.

The highest signal strength is determined by the resonance. Just like a radio's variable capacitor causes the IRL circuit to resonate at specific frequencies which is what allows you to modulate that frequency with audio and have only your audio be a high enough amplitude to be picked up by the amp.

Why am I having this conversation :(

 

[sophiecentaur]

Well yea, we are not saying it is not. Color is a mental interpretation of frequency.

Why do you just say "frequency". I keep on telling people that there are always multiple frequencies involved - usually a continuous spectrum and very wide band - take the 'blue' sky, for instance. The colour we appreciate is a very simple analysis of the total spectrum that we receive (modified by other factors, too).

 

[sophiecentaur]

The highest signal strength is determined by the resonance. Just like a radio's variable capacitor causes the IRL circuit to resonate at specific frequencies which is what allows you to modulate that frequency with audio and have only your audio be a high enough amplitude to be picked up by the amp.

Why am I having this conversation :(

I can't think. It is inaccurate and nothing to do with how we actually see and appreciate colour. Do you actually know what a resonance is?

 

[LostConjugate]

I can't think. It is inaccurate and nothing to do with how we actually see and appreciate colour. Do you actually know what a resonance is?

Here is a quote about resonance.

In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies. At these frequencies, even small periodic driving forces can produce large amplitude oscillations, because the system stores vibrational energy.

You can say the cones get "excited" but the proper explanation is resonance.

 

[LostConjugate]

Why do you just say "frequency". I keep on telling people that there are always multiple frequencies involved - usually a continuous spectrum and very wide band - take the 'blue' sky, for instance. The colour we appreciate is a very simple analysis of the total spectrum that we receive (modified by other factors, too).

very wide?

I am not sure if you are grasping how small a range of frequencies a cone resonates with. It is something like .000001% of the entire electromagnetic spectrum (just guessing). Photons can carry all sorts of energy anywhere from 10^-33eV to 10^28eV I think.

 

[D H]

When someone is color-blind, does that mean that their cones don't work right or does it means something happens to the resulting signal that makes the brain not distinguish it in the same way as the brain of someone who recognizes color?

It means their cones don't work right. The signals going from the eye to the brain differ in some qualitative way in a colorblind person compared to someone with a fully functional suite of rods and cones.

The idea that color is subjective is suspect. More than 90% percent of the people see more or less the same color for a given frequency spectrum.

 

[sophiecentaur]

very wide?

I am not sure if you are grasping how small a range of frequencies a cone resonates with. It is something like .000001% of the entire electromagnetic spectrum (just guessing). Photons can carry all sorts of energy anywhere from 10^-33eV to 10^28eV I think.

So you are saying, contrary to every other source of information, that we don't have three sets of wide band receptors but a huge number of different receptors, each tuned to a separate frequency - or does each one have some sort of output which tells the brain which actual frequency has been received? This is a truly revolutionary idea and I would love to know where you read about it.
If you look at the sensitivity curves of the three receptors you will see that the sensitivity range of each receptor covers most of the optical region so that they all overlap significantly. They just have peaks in different places. (Google colour sensitivity curves) This gives three signals of different relative levels which allows your brain to assign a colour to the light entering the eye for a wide range of spectra. This was all established nearly a hundred years ago and modern colourimetry uses more or less exactly the same system. As for resonance, the bandwidth of the receptors can be estimated when you consider that the optical region covers about an octave and that the half power width of the sensitivity is about 1/3 of that. This gives a fractional bandwidth of, perhaps 1/6. Resonance is not the only mechanism for frequency selectivity - you can make a bandpass filter with only Rs and Cs so no resonance is needed. You are just using the wrong terms for your ideas. What are you "grasping" from what you have read?

 

[LostConjugate]

Resonance is not the only mechanism for frequency selectivity - you can make a bandpass filter with only Rs and Cs so no resonance is needed. You are just using the wrong terms for your ideas. What are you "grasping" from what you have read?

I am no electrical engineer but isn't that still a form of resonance that is just prevented from completing a full oscillation?

I am not disagreeing with you that the cones respond to a range of frequencies. I never did disagree with that, there are only 3 cones, they each (we will say) get excited within a "range" of frequencies.

You could also argue that if I show up at 7pm that I am actually showing up somewhere between 6:50pm and 7:10pm or 6:59:45pm and 7:00:70pm. No disagreement.

 

[Drakkith]

very wide?

I am not sure if you are grasping how small a range of frequencies a cone resonates with. It is something like .000001% of the entire electromagnetic spectrum (just guessing). Photons can carry all sorts of energy anywhere from 10^-33eV to 10^28eV I think.

I don't see how resonance has much of any meaning here. A cone cell does not oscillate back and forth nor does it store vibrational energy. Only a certain range of frequencies will make it to the cone cell and cause the chemical reaction that eventually results in a signal being sent to the brain. Attempting to explain senses and other things in terms of "resonance" is simply confusing in this circumstance. While one could argue how resonance applies to the senses and consciousness, that is beyond the scope of the current thread and belongs elsewhere in my opinion.

In regards to color perception, we need to be clear with what we mean. A cone that is labeled as Blue responds BEST to blue light. To my knowledge it has a cone shaped section covered with a pigment that absorbs less light near the blue end of the spectrum and more light as the frequencies get further away, hence giving it the response range it has. The retinal doesn't particularly care what frequency of light within this range hits it. The other 2 cells operate similarly but react better to different portions of the visual spectrum. The combination of the 3 cells and the signals they send determines the input the brain receives and interprets.

So obviously wavelength plays a great role in color perception, but it does not play the ONLY role. Physical damage to the cone cells, nerves, or brain can cause someone to have an altered perception of color. In addition, your mental state can also cause you to perceive color differently. (Among perceiving other things differently as well)

Furthermore, your brain compensates for different light intensities and even partially for entirely missing frequencies. Take out part of the blue end of the spectrum from a light source and you can usually still tell what color an object is as long as you have something to compare it too. Not as well as you could in pure white light, but enough for everday situations usually. Taken out more frequencies obviously reduces the effectiveness of this in general.

I don't see it as simple as saying color perception is based on X. A basic understanding of the whole process is needed in my opinion. Also, I see a difference between what you see normally and what you might see under the influence of drugs, injury, or something else that affects color perception. Just because your brain puts the signals together doesn't mean that it is the only thing responsible for color perception unless the discussion is ONLY about the way the brain puts together those signals and interprets them. (Which this discussion doesn't appear to be that focused to me)

 

[LostConjugate]

Only a certain range of frequencies will make it to the cone cell and cause the chemical reaction that eventually results in a signal being sent to the brain.

So this chemical reaction is not due to electron configurations resonating with the specific frequency range?

Everything else you said, I agree with.

 

[Drakkith]

When someone is color-blind, does that mean that their cones don't work right or does it means something happens to the resulting signal that makes the brain not distinguish it in the same way as the brain of someone who recognizes color?

If their cones are flawed, then I don't think my question is relevant to this discussion, but if their cones are OK, but the brain sees black and white doesn't this say something about how "color" is not frequency but a mental interpretation?

Most people who are color blind have a problem with their cone cells. Sometimes they can be missing an entire set of cone cells and only have two inputs instead of 3. Sometimes the cone cells have their response ranges shifted, resulting in much less of an ability to distinguish between certain colors, such as my dad seeing Red and Green as being almost the same color.

It is possible, to my knowledge, for something like brain or nerve damage to cause color blindness as well. The effects of that are probably much more varied than deficient cone cells.

 

[Drakkith]

So this chemical reaction is not due to electron configurations resonating with the specific frequency range?

Everything else you said, I agree with.

As far as I know, no. The pigment filters out wavelengths and only let's light within its range make it to the retinal to activate it. A stronger response simply means that the wavelength has a better chance of getting through the pigment. I'm am not an expert on this, so I could very possibly be wrong.