To be correct - what is color, actually?

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To be correct - what is color, actually?

Postby vivian maxine on July 21st, 2016, 11:19 am 

Not meaning to start a debate. This question came to me as I read about how colors of objects change as the amount of light striking them change.

To be both scientifically and semantically correct, does an object have color? Or does the object only reflect color depending on how much light it receives -- and, I suppose, the elements that make up that object?

Suddenly, I am asking myself What is color? And what is color's origin?
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Re: To be correct - what is color, actually?

Postby Eclogite on July 21st, 2016, 11:44 am 

When we talk about the colour of an object we are generally talking about its colour as perceived by us, or in more scientific contexts, as measured by appropriate instrumentation. The latter means what is the relative intensity of light at different frequencies.

The frequency of the light, IIRC, is determined by the energy of the photon released by an atom when an electron drops to a lower energy orbital.
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Re: To be correct - what is color, actually?

Postby Braininvat on July 21st, 2016, 11:52 am 

If we are talking about ordinary things around us, they generally "have" pigments, which are chemicals that absorb some wavelengths of light while reflecting others. Consider a yellow rose. The sunlight strikes the rose, and sunlight has wavelengths of light that range all through the visible spectrum. (you see this range, when a prism breaks up a sunbeam into a "rainbow" of all those wavelengths, from red to violet). Some of the light is absorbed, but the wavelengths that correspond to yellow (top of my head, I'm guessing that's around 570 nanometers....I'd have to look it up to give a precise range) are reflected back and observed as "color."

Other things, like lasers, produce their own light, they are emitters, IOW, and they have a handy quality in that they produce light that is monochromatic - this means, all the light emitted is the same wavelength. The red laser the grocery checker is using to read prices might be producing monochromatic light of 620 nanometers. This is different from the red rose, which is reflecting a range of wavelengths that are around that figure of 620.

Distinguishing these wavelengths of visible light is useful to many creatures, like us, so our visual system has evolved an ability to do so. Other animals, which have less need of separating out colors, see only light and dark, shapes and countours, which are sufficient for them to survive in their environment. Their total range of wavelengths visible to them, however, may differ a bit from ours. Perhaps seeing infrared helps them see things at night that we would be blind to, and helps them avoid predators or find sources of warmth.
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 21st, 2016, 12:07 pm 

So, first answer is: "It gets complicated". Second answer: "Pigment is involved in it." I think this is going farther than I expected. Can we say whether color is matter or non-matter? Or is it an interaction between two entities?

All of this really is leading somewhere. I've been reading about Descarte's effort to distinguish between body and mind. I'm not ready to say what I thought but am thinking on this idea of non-material things interacting with material things.

More on that manana.
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Re: To be correct - what is color, actually?

Postby zetreque on July 21st, 2016, 1:04 pm 

It sounds like you are asking more about the philosophical side like beauty is in the eye of the beholder. What was said is true that in reality an object will emit a certain wavelength of light no matter what. Then you have the receptor or receptors. Some people claim to be color blind in that their receptors are different so their mind see's a different "color". In this case you have
1. A material thing that has electrons changing energy orbital levels
2. sending off something with no mass aka a photon which is a packet of energy
3. coming into contact with something real/mass again, the rods and cones on the back of your eye
4. converting into another "energy signal?"
5. which is sent to the brain aka the "mind" where you find the debate between body and mind.

Now to make things even more complicated, what about sound? Everyone ignores sound which is just as important to the senses as light. I read something that life evolved to interact the world through sound before it did light. In sound you have specific frequencies again, but then when it comes into contact with the ear, can there be things like sound blindness? or a different perception of sound? Especially when you have overlapping frequencies based on your orientation in relation to the object emitting the sound.
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 21st, 2016, 1:39 pm 

Sound would work too in where I am going. This particular question about color - this particular thread - is really separate from where I started. I just suddenly stopped to wonder if that tomato the article is talking about really has color or is it just reflecting color. I forgot about pigment which does have mass and almost takes us back to the beginning of what is color. The original colors used in prehistoric art were definitely mass. Iron oxide for one. Many others.

I'll get back to Descartes and start a new thread because it will not fit here. It's an entirely different question that - as I said - this just happened to grow out of. And talk of sound might be an even better example there.

Later. I need to do some re-reading. Thanks much.
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Re: To be correct - what is color, actually?

Postby dandelion on July 22nd, 2016, 12:59 am 

Context may be a factor,
http://brainden.com/color-illusions.htm
:)
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Re: To be correct - what is color, actually?

Postby zetreque on July 22nd, 2016, 1:32 am 

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Re: To be correct - what is color, actually?

Postby neuro on July 22nd, 2016, 5:47 am 

Hi Vivian.
Strictly speaking, coloe is not a property of objects.
Color is a property of light: its composition in terms of the amount of light present at each particular frequency (wavelength).

Any object will appear to "have" a color, depending on which wavelengths it absorbs and which ones it reflects. If it absorbs all wavelengths but in the region of blue, then it "has" the color blue. However, it is obvious that if we illuminate it with a light that does not contain any blue wavelengths (dark yellow, for example), then the object will not reflect any light and will no more be blue, but simply black.

This story is physically trivial. However, it has an enormous conceptual and philosophical relevance: it says that an object cannot be defined completely based on its internal structure; it would be useless. In order to define an object we have to consider how it "appears" from outside, how it interacts with the external world, how its interface with the external world works.

The story is very reminiscent of Goedel theorem: either you try and get a consistent description of the object (properties, laws and mechanisms that fully describe it in isolation), but this will not be a complete description; or you try and get a complete description (considering the possible interactions of the object with the external world - such as its "color" for example) but it will not be possible for it to be consistent, because the object in isolation and its interactions with the external world are not described by the same properties, mechanisms and laws.

In other words, you may describe the chemical structure of a body, according to a consistent set of definitions and laws; but you cannot apply such laws to tell what is the color of the object (consistent, incomplete knowledge).
Conversely, you can describe the chemical structure of a body and also tell its color, but even though this might now be a complete description, it will be inconsistent, because if you move the object to another location its color will change.
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 22nd, 2016, 7:18 am 

neuro » July 22nd, 2016, 4:47 am wrote:Hi Vivian.
Strictly speaking, coloe is not a property of objects.
Color is a property of light: its composition in terms of the amount of light present at each particular frequency (wavelength).

Any object will appear to "have" a color, depending on which wavelengths it absorbs and which ones it reflects. If it absorbs all wavelengths but in the region of blue, then it "has" the color blue. However, it is obvious that if we illuminate it with a light that does not contain any blue wavelengths (dark yellow, for example), then the object will not reflect any light and will no more be blue, but simply black.

This story is physically trivial. However, it has an enormous conceptual and philosophical relevance: it says that an object cannot be defined completely based on its internal structure; it would be useless. In order to define an object we have to consider how it "appears" from outside, how it interacts with the external world, how its interface with the external world works.

The story is very reminiscent of Goedel theorem: either you try and get a consistent description of the object (properties, laws and mechanisms that fully describe it in isolation), but this will not be a complete description; or you try and get a complete description (considering the possible interactions of the object with the external world - such as its "color" for example) but it will not be possible for it to be consistent, because the object in isolation and its interactions with the external world are not described by the same properties, mechanisms and laws.

In other words, you may describe the chemical structure of a body, according to a consistent set of definitions and laws; but you cannot apply such laws to tell what is the color of the object (consistent, incomplete knowledge).
Conversely, you can describe the chemical structure of a body and also tell its color, but even though this might now be a complete description, it will be inconsistent, because if you move the object to another location its color will change.


Thank you, neuro. That was my thinking but I didn't want scientific facts to throw me a curve. Objects do not have color; they reflect color depending on amount of light. It would seem a bit clumsy to try to describe a child's ball that way but - for me - it's now back to the drawing board. I appreciate your explanation. The rest is fascinating information.
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Re: To be correct - what is color, actually?

Postby Braininvat on July 22nd, 2016, 8:42 am 

That was basically what I posted earlier. I would add that a complete chemical description of an object could include the chemicals absorption and emission of different wavelengths of light. In that sense, objects can "have" color. As Neuro clarified, this will mean that a complete description includes interactions with the external environment.
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 22nd, 2016, 9:03 am 

Braininvat » July 22nd, 2016, 7:42 am wrote:That was basically what I posted earlier. I would add that a complete chemical description of an object could include the chemicals absorption and emission of different wavelengths of light. In that sense, objects can "have" color. As Neuro clarified, this will mean that a complete description includes interactions with the external environment.



It's that word "interactions" that I'm clutching to. Light (a "not-physical mass) is interacting with a physical mass (pigment). I didn't get to re-read the Descartes article last night. Must get back to that or I'm not making sense. Thank you, BIV.
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Re: To be correct - what is color, actually?

Postby neuro on July 22nd, 2016, 1:27 pm 

careful Vivian!

light = a physical non-mass (not a nonphysical mass)

and don't forget that mass is nothing more than a certain "mode of being" of energy (mass-less particles are another "mode of being" of energy)
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Re: To be correct - what is color, actually?

Postby neuro on July 22nd, 2016, 1:34 pm 

Sorry BiV, I didn't mean to underestimate your explanation.

My work is to explain to students, and I simply find it useful to explain things in several different (possibly quite similar) ways. And here I was too strongly tempted to turn the question into a philosophical problem, that of defining a system per se but ALSO its boundary - which requires knowledge not only of the system but also of the laws prevailing outside (independent of) the system itself.
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 22nd, 2016, 1:36 pm 

neuro » July 22nd, 2016, 12:27 pm wrote:careful Vivian!

light = a physical non-mass (not a nonphysical mass)

and don't forget that mass is nothing more than a certain "mode of being" of energy (mass-less particles are another "mode of being" of energy)


Hmmm? How can we have a physical non-mass? Mass is a mode of being of energy?

Now I admit to total confusion. I think I've bumped into a totally different meaning of "mass". Seems to me this happened with another term just recently.

All right, I'll work on this as soon as I finish with Decartes' problem. I think I have it nailed down. Not solved! Just pinned.

Thank you. To be honest, I've suspected for some time that "mass" was being used in a far different way than my concept of mass.
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Re: To be correct - what is color, actually?

Postby zetreque on July 22nd, 2016, 1:40 pm 

Mass is Energy
Energy is Mass
It gives us nuclear bombs.

Just because it's energy doesn't mean it's not real. Is that why you call it physical neuro? Physical meaning real and can interact or be felt?
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 22nd, 2016, 1:44 pm 

neuro » July 22nd, 2016, 12:34 pm wrote:Sorry BiV, I didn't mean to underestimate your explanation.

My work is to explain to students, and I simply find it useful to explain things in several different (possibly quite similar) ways. And here I was too strongly tempted to turn the question into a philosophical problem, that of defining a system per se but ALSO its boundary - which requires knowledge not only of the system but also of the laws prevailing outside (independent of) the system itself.


Not at all, Neuro. I really do appreciate corrections and explanations. As I just posted, I've rather suspected there was something going on with that word that I needed to dig into. And there still is. I'll get with it.

As for the philosophical problem - huh? This reminds me of a teacher we had at university who had just explained something. She then looked around and said "You all look so perplexed. Yet you don't ask any questions." I piped up and said "that's because we don't know what to ask.

Is the philosophical problem beyond me?
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 22nd, 2016, 1:46 pm 

zetreque » July 22nd, 2016, 12:40 pm wrote:Mass is Energy
Energy is Mass
It gives us nuclear bombs.

Just because it's energy doesn't mean it's not real. Is that why you call it physical neuro? Physical meaning real and can interact or be felt?


Thank you, too, Zetreque. There are clues in your comments. Viv
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 24th, 2016, 12:22 pm 

neuro » July 22nd, 2016, 12:34 pm wrote:Sorry BiV, I didn't mean to underestimate your explanation.

My work is to explain to students, and I simply find it useful to explain things in several different (possibly quite similar) ways. And here I was too strongly tempted to turn the question into a philosophical problem, that of defining a system per se but ALSO its boundary - which requires knowledge not only of the system but also of the laws prevailing outside (independent of) the system itself.


My apologies, Biv and Neuro. Bad vision again. Bad reading. Viv
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Re: To be correct - what is color, actually?

Postby Braininvat on July 24th, 2016, 4:50 pm 

No apologies needed from anyone. Neuro, you considerably clarified some points I had made. Didn't mean to sound touchy.
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Re: To be correct - what is color, actually?

Postby Graeme M on July 28th, 2016, 10:52 pm 

This is a question I've occasionally tussled with in my mind. I'm not sure if strictly speaking I'm coming at it from the same angle as this thread, but here goes. I'd appreciate any comments on how close I am with this mental model.

From what I've read (and this is not a lot so I likely have only a shallow grasp of the matter) and thought about, it seems to me that color is not a property of light in any way at all. Color is entirely an inner representation of the effects of electromagnetic radiation on our visual receptors. I know at a general level how that actually works, but in simple terms, my understanding is that the ratio of responding cells signals the brain which generates a representation which we call color. If no cells respond, then the "color" represented is black (ie no signal). If all or a majority of cells respond at largely equal levels of intensity, the result is white (ie a homogeneous signal). If some cells respond, the intensity/response ratio of these will produce a color.

Evolutionarily, I'd assume that eyes (and brains) would initially have responded in a somewhat simple fashion - light or not, followed by shades of light, so I'd go out on a limb and suggest the earliest eyes did monochrome only. Color would have come later, but black and white etc would remain at either ends of the "spectrum", rather like bookends. Black white and grey-scale representations are older constructs that bleed into the more recent color representations.
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 29th, 2016, 6:59 am 

Sounds good to me, Graeme. Very much depends on the eyes. Remember that some animals (cats, e.g.) can see more in the dark than we can. So, do they have more of the "right" cells?

[quote=Graeme"]it seems to me that color is not a property of light in any way at all. Color is entirely an inner representation of the effects of electromagnetic radiation on our visual receptors.[/quote]

Something to ponder. Thank you.

Another thing I wonder about when thinking of color. Do we all see the same thing when we say a color word. Is the "green" that I see totally different from what you call "green". Perhaps what you see as "green" is, to someone else "purple"?

Just a curiosity question.
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Re: To be correct - what is color, actually?

Postby Graeme M on July 29th, 2016, 7:20 am 

Hey Vivian, first bear in mind I have only rudimentary knowledge about this stuff. I have only the most basic of science education and what I learned back then I've mostly forgotten. So pretty much everything these days is new to me!! I also can never find the time to really dig into a lot of these things so I do a quick look around and then wake up in the night and lie there thinking about it trying to get it all straight. No idea how close I am but I have a fine time thinking about stuff...

As far as vision goes, yes it depends on the kinds of receptor cells in the retina. Rods respond to light alright but only in shades of black and white. They are more sensitive to light intensity and there are more of them. Cones of course do colour. I assume that variations on these are found in other animals eyes. I believe I've read that in some creatures the cells respond to different wavelengths too (eg ultra-violet).

In terms of our experience, I think I am on safe ground to observe that pretty much nothing we experience actually exists in the "real world". Outside our heads, there is no colour, no illumination, no sounds, no hot or cold, no hard or soft etc etc. I find that absolutely astounding, and I sometimes struggle to understand what that really means.

Colour blows me away, and I wish I had time to really learn more about it.

As for what we see and whether it is the same as someone else, I have an idea about that which I cannot explain. Simply, I do suspect that the response curves for eyes must have some differences across individuals because we are organic and not digital. I don't think that leads to you perceiving green differently from me, for the simple reason that I don't believe that anyone perceives green to begin with. That strays into philosophy, but I simply don't think the 'qualia" of experience exist. Make of that what you will...
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Re: To be correct - what is color, actually?

Postby vivian maxine on July 29th, 2016, 8:49 am 

We are in the same boat, Graeme. No problem with just wondering. But then, there's this:

Graeme wrote:I don't think that leads to you perceiving green differently from me, for the simple reason that I don't believe that anyone perceives green to begin with. That strays into philosophy


Now you do have me wondering. I don't think I'll go there. I'm falling behind with today's promises.
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Re: To be correct - what is color, actually?

Postby neuro on August 1st, 2016, 6:49 am 

About light vs. color:
you might consider that we have cells in the retina that express a specific kind of light sensitive protein/pigment (they are neither cones nor rods and are called "intrinsically photosensitive retinal ganglion cells"); these cells do not project to visual pathways in the brain, but to the supraoptic nucleus of the hypothalamus, where they contribute in regulating melatonin release (by the pineal gland) and hormone circadian rhythms.
This system is not sophisticated enough to let us analyse an image or distinguish color. So, I would agree with Graeme that perception of light presumably precedes - in evolutionary terms - perception of colors.

About subjective perception of color: unless one is affected by Daltonism (the lack of one of the visual pigments in cones), there is no reason to assume that one's perception of green should differ from anybody else's perception of green. However, this cannot be demonstrated, obviously, so that a lot of flavoured food for thought is left to philosophers who like to discuss the ontology of "qualia" (subjective aspects of perception).
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Re: To be correct - what is color, actually?

Postby vivian maxine on August 1st, 2016, 9:32 am 

neuro » August 1st, 2016, 5:49 am wrote:About light vs. color:
you might consider that we have cells in the retina that express a specific kind of light sensitive protein/pigment (they are neither cones nor rods and are called "intrinsically photosensitive retinal ganglion cells"); these cells do not project to visual pathways in the brain, but to the supraoptic nucleus of the hypothalamus, where they contribute in regulating melatonin release (by the pineal gland) and hormone circadian rhythms.
This system is not sophisticated enough to let us analyse an image or distinguish color. So, I would agree with Graeme that perception of light presumably precedes - in evolutionary terms - perception of colors.

About subjective perception of color: unless one is affected by Daltonism (the lack of one of the visual pigments in cones), there is no reason to assume that one's perception of green should differ from anybody else's perception of green. However, this cannot be demonstrated, obviously, so that a lot of flavoured food for thought is left to philosophers who like to discuss the ontology of "qualia" (subjective aspects of perception).


Thank you, Neuro. Good to know this because I've wondered for many a year if we all see the same color when we name a color we see. Maybe, some day, somebody will find a tiny area in the brain that settles the matter.
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Re: To be correct - what is color, actually?

Postby neuro on August 1st, 2016, 9:49 am 

vivian maxine » August 1st, 2016, 2:32 pm wrote: Maybe, some day, somebody will find a tiny area in the brain that settles the matter.


Vivian,
I fear I was not clear at all.
Neurologically, we DO PERCEIVE the same color exactly the same way (apart from possible defects in the retina, the optic nerve or the cortex).

The philosophical question of "qualia" (i.e. the impossibility of knowing what another subject SUBJECTIVELY feels, except just assuming they feel the same we would feel) will never be settled by any scientific observation on the brain.
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Re: To be correct - what is color, actually?

Postby vivian maxine on August 1st, 2016, 10:36 am 

neuro » August 1st, 2016, 8:49 am wrote:
vivian maxine » August 1st, 2016, 2:32 pm wrote: Maybe, some day, somebody will find a tiny area in the brain that settles the matter.


Vivian,
I fear I was not clear at all.
Neurologically, we DO PERCEIVE the same color exactly the same way (apart from possible defects in the retina, the optic nerve or the cortex).

The philosophical question of "qualia" (i.e. the impossibility of knowing what another subject SUBJECTIVELY feels, except just assuming they feel the same we would feel) will never be settled by any scientific observation on the brain.


All right. I mis-read. I thought you meant we cannot actually demonstrate that A sees the same thing B sees when the two look at the same color. I do not see the connection to "feel". Let me think about it.
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Re: To be correct - what is color, actually?

Postby neuro on August 1st, 2016, 11:02 am 

vivian maxine » August 1st, 2016, 3:36 pm wrote: I do not see the connection to "feel". Let me think about it.

It is not a scientific problem.
The philosophical problem is: provided your brain and the brain of another person display exactly the same pattern of activity, how can you tell the other person "feels" exactly what you "feel"?

There is no experimental way to tell (except, very roughly, by sharing the verbal descriptions of what each of the two seems to feel; however, in the particular case it is not so easy to describe how one feels the green color...). Neither is there any solid logical / philosophical way.
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Re: To be correct - what is color, actually?

Postby vivian maxine on August 1st, 2016, 11:15 am 

Red is hot; green is cool; blue is soothing. Black is depressing - and why are so many of our authors now using black with, of all things, dark gray unreadable print?

Yet, if someone else doesn't feel the same about some of those colors, he still does not know how I feel. Or he may know how I feel but disagree.

Uncertainty on both our parts. Thank you.
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