Is Black a Colour? Examining the Definition and Perception of Black as a Colour

[ZapperZ]

Actually ZapperZ, his post is factual and not philosophical. Colors as we experience them are created in the brain and are not a property of the EM wavelengths they represent. There is no objective reason that EM wavelengths between 625 and 740 nanometers should look red to us. There's no reason any color should be anything but a shade of grey. Our brains add the spice of colors as we percieve them. This is a neurological fact that you could confirm with Mentor Hypnagogue or selfAdjoint.

It does become "philosophical" when you start to consider if something "exist". "color" is how we perceive certain EM frequency. It isn't quantitatively accurate, but it is certainly not something we imagined. It is no different than having a trigger that goes BAM when an EM radiation of a certain frequency hits it.

If you accept his logic as color not existing, then you should accept also that you don't exist, because all you are is what *I* perceived in my brain. This is what I mean as it being no longer a physics discussion.

Zz.

 

[zoobyshoe]

It does become "philosophical" when you start to consider if something "exist". "color" is how we perceive certain EM frequency. It isn't quantitatively accurate, but it is certainly not something we imagined. It is no different than having a trigger that goes BAM when an EM radiation of a certain frequency hits it.

If you accept his logic as color not existing, then you should accept also that you don't exist, because all you are is what *I* perceived in my brain. This is what I mean as it being no longer a physics discussion.

Zz.

I think I understand your objection to what he said.

When I read it, I disliked the way he said it, but didn't take it to be the grounds of anything like a developed philosophical stance, just a poorly expressed, over exited reaction to an "amazing" piece of information. My mind was boggled when I first found this out as well, so I refrained from pointing out that saying "We only think it exists" is not an articulate way of expressing the phenomenon of our experience of color. I thought he just lacked the sophistication to phrase it in a way that wasn't inadvertantly misleading.

 

[Danger]

We have to suppose this was the same kind of accidental mutation that goes on all the time in evolution. Despite being a "fictional" perception it proved so much more useful in sorting the environment out than just seeing things in many shades of grey, that the first people who saw this way did better than their black and white visioned contemporaries and eventually supplanted them.

I can't remember the details, but a SciAm article a couple of issues back on how birds see provides evidence that early humans (or their forebearers) possessed 4 types of cone cells and degraded to the 3 that we now have.

 

[zoobyshoe]

I can't remember the details, but a SciAm article a couple of issues back on how birds see provides evidence that early humans (or their forebearers) possessed 4 types of cone cells and degraded to the 3 that we now have.

I read that, at least some birds, can see in the ultraviolet range. So it sounds like the article you read is suggesting humans once could as well.

You recall what made them suspect this?

 

[Danger]

Not right off, but I still have the issue at home. I think that it was by tracking eye development through various stages of evolution in general to see where birds and mammals differentiated as to visual structures. I'll look for it when I'm done work.

 

[NoTime]

I can't remember the details, but a SciAm article a couple of issues back on how birds see provides evidence that early humans (or their forebearers) possessed 4 types of cone cells and degraded to the 3 that we now have.

Actualy, some still do, but IIRC its lower into the red not UV.

A small mention of tetrachromats in the following
http://en.wikipedia.org/wiki/Color#Spectral_colors

 

[zoobyshoe]

Actualy, some still do, but IIRC its lower into the red not UV.

A small mention of tetrachromats in the following
http://en.wikipedia.org/wiki/Color#Spectral_colors

But not infra-red, (which would be cool):

Also, evidence suggests that some very few humans are tetrachromats, a phenomenon which presumably arises when an individual receives two slightly different copies of the gene for either the medium- or long-wave cones. It can be supposed that, for genetic reasons, the small numbers of human tetrachromats that do exist are overwhelmingly female. Their color discriminations are only slightly enhanced, but their brains do appear to adapt to use the additional color information.

 

[Chaos' lil bro Order]

Originally Posted by Chaos' lil bro Order
Dave gives the best answer so far. This definition satisfies that an object can be black because any incident light is absorbed by it and that an object can be black because there is no incident light whatsoever. The point is, as Dave succinctly pointed out, is that 'no light is emitted from [the object].'

All other discussion is wrong.

Ouch! Can't disagree more. Is a perfect reflector black?

I'm not sure I understand your objection Gokul. I don't recall saying perfect reflection makes an object black. Can you elaborate please.

 

[Chaos' lil bro Order]

Bees can see the UV rays emitted from flowering plants (read David Bodanis' 'The secret house').

Snakes have pits on their head that detect Infrared (re: hunting for mice at night).

Humans have a so-called 'third eye' technically called the pineal gland located under the forehead. Science does not know much about this gland and many suppose its a vestigial remnant. Interestingly, many birds have this gland much closer to the surface of their forehead (possibly to detect the Earth's magnetic field for migration compassing purposes?)

People always talk about cones as being our 'color detectors', but few people know that cones are actually at the back of the retina. Incident light must first travel through many layers of cells in the Plexiform layer of the retina. These cells include (in order of interaction with incident light) Ganglion cells, Amacrine cells, Bipolar Cells, Horizontal Cells AND THEN cones and rods. Many researchers believe Ganglion cells may also act as photoreceptors in addition to the familiar cones and rods. It is also wise to postulate that both Ganglion cells and cones/rods are photoreceptors and their redundancy is part of a fact-checking error correction system. This postulate gains extra credence by the fact that there are many subsystems in the retina that WE KNOW to be utilizers of a fact-checking error correciton system (re: feedback loops in horizontal cells).

If anyone has a question, please ask it, as this is my area of expertise. Finally I won't have to step on Zapper's QM knowledge or SpaceTIger's Cosmology knowledge!

 

[Gokul43201]

I'm not sure I understand your objection Gokul. I don't recall saying perfect reflection makes an object black. Can you elaborate please.

A perfect reflector has an emissivity of zero (from energy conservation and Kirchoff's Law). So, if it emits no light...

 

[DaveC426913]

A definition was put forth (https://www.physicsforums.com/showpost.php?p=1091947&postcount=19") that "A thing is black if it absorbs all the visible radiation incident upon it". This is a needless condition - whether the object absorbs anything is irrelevant. The only requirement for an object to be black is that no photons are coming from the object. (eg. In a dark room, the object absorbs no photons.)

A perfect reflector has an emissivity of zero (from energy conservation and Kirchoff's Law). So, if it emits no light...

I think you're bifurcating bunnies here. Correct me of I'm wrong but, without worrying about the details, an object reflects photons by absorbing them and re-emitting them. We don't call this emission, but technically it is.

Nonetheless, if "no emissions" is technically unacceptable, then can we come up with a term that means "no photons leave the object"?

 

[Andrew Mason]

A definition was put forth (https://www.physicsforums.com/showpost.php?p=1091947&postcount=19") that "A thing is black if it absorbs all the visible radiation incident upon it". This is a needless condition - whether the object absorbs anything is irrelevant. The only requirement for an object to be black is that no photons are coming from the object. (eg. In a dark room, the object absorbs no photons.)

But in your definition colour is not an attribute of the object but an attribute of the light that falls on it.

AM

 

[Farsight]

Zoobyshoe, I was rather trying to keep things simple. And fun.

Zapper, in my humble opinion, whether colour actually exists is something more than philosophy. What definitely exists is frequency, a cyclic variation. We can measure this. Yes, we can assign a colour, but the colour is not actually out there in the world we are trying to study. It's an internal label for information processing. In similar vein we can model molecules and work out the arrangement of atoms, but the smell of them is not actually there either. Going further we can talk about heat, a "derived effect" of motion. We all know about heat and how it burns, but we tend to start talking about heat flow as if heat is an actual fluid. Or people talk about pure energy as if it's something you can hold in your hand, forgetting that it is the property of a system. My point is that the science becomes coloured, corrupted even, by our perception, and the loose linguistic baggage that we take for granted. Rigour is compromised.

Andrew, perhaps that should be an attribute of the light that comes from it.

 

[ZapperZ]

Zapper, in my humble opinion, whether colour actually exists is something more than philosophy. What definitely exists is frequency, a cyclic variation. We can measure this. Yes, we can assign a colour, but the colour is not actually out there in the world we are trying to study. It's an internal label for information processing. In similar vein we can model molecules and work out the arrangement of atoms, but the smell of them is not actually there either. Going further we can talk about heat, a "derived effect" of motion. We all know about heat and how it burns, but we tend to start talking about heat flow as if heat is an actual fluid. Or people talk about pure energy as if it's something you can hold in your hand, forgetting that it is the property of a system. My point is that the science becomes coloured, corrupted even, by our perception, and the loose linguistic baggage that we take for granted. Rigour is compromised.

It is one thing to say such a description is inaccurate. It is ANOTHER to say it doesn't exist! I would say that you don't exist either.

I would put it to you that assigning a number to the value of frequency is no different than assigning "color". You are still putting a "label" on it. You just don't realize it.

Zz.

 

[Farsight]

Actually Zapper, the existence of my consciousness is a very interesting question. I can't see it, or smell it, or weigh it, or touch it. I can't prove it exists. All I can do is experience it. And it is all that I do experience. It's nothing and everything. It's totally imaginary, yet totally real. It doesn't exist, or does it? Let's not consign this sort of thing to philosophy just because we can't be bothered to think up an experiment. Especially seeing as it rather reminds me of money. And money reminds me of energy.

 

[ZapperZ]

Actually Zapper, the existence of my consciousness is a very interesting question. I can't see it, or smell it, or weigh it, or touch it. I can't prove it exists. All I can do is experience it. And it is all that I do experience. It's nothing and everything. It's totally imaginary, yet totally real. It doesn't exist, or does it? Let's not consign this sort of thing to philosophy just because we can't be bothered to think up an experiment. Especially seeing as it rather reminds me of money. And money reminds me of energy.

If you don't think that what you said here does not belong in physics, then there's nothing else to be said to you.

Zz.

 

[Farsight]

Anyhow, is black a colour?

Yes. It is our internal label for frequency 0.

Edit: Maybe not physics, Zapper. But Brain Science, not philosophy.

 

[NoTime]

But not infra-red, (which would be cool):

I might have the longer wave version of the long-wave cones.
In any event I can see when supposedly IR leds and lasers are opereating.
For example most remote controlers.
Exposed led ones are fairly easy to see. Some of the covered ones are barely (or not) detectable and the room lights needs to be dimed, but I don't have to wait for dark adaption.

I wonder how common this is.

Bigest thing I've noticed is that sometimes people will call red for what I would call a red/orange

 

[Farsight]

That sounds unusual, NoTime. I've heard of people who can see some way into the UltraViolet range, but not the other way. Maybe there's something here:

http://www.4colorvision.com/files/tetrachromat.htm

"Tan reported, and Griswold & Stark confirmed, that the spectral response of aphakic humans extended well into the area of 300-400 nm..."

 

[Farsight]

All: I think this has been posted up before, apologies if it's old news. But it's particularly relevant here because it tells us something important about perception and colour, which we need to appreciate when we're trying to be rational about questions like Is black a colour? It seems rather incredible, but in simple terms you end up with something like this:

Q: When is blue yellow?
A: When they're both grey.

Try it:

http://www.echalk.co.uk/amusements/OpticalIllusions/colourPerception/colourPerception.html

 

[Chaos' lil bro Order]

A perfect reflector has an emissivity of zero (from energy conservation and Kirchoff's Law). So, if it emits no light...

If something emits no light, its a perfect blackbody. A perfect blackbody has an emissivity = 1. A perfect reflector has an emissivity = 0. You are intertwining reflection and emission as the same concept. If something emits no light, its black. Case solved.

 

[Chaos' lil bro Order]

It is one thing to say such a description is inaccurate. It is ANOTHER to say it doesn't exist! I would say that you don't exist either.

I would put it to you that assigning a number to the value of frequency is no different than assigning "color". You are still putting a "label" on it. You just don't realize it.

Zz.

This notion has been beaten to death in the Dr.Chinese 'Realism' post. Everything we know is a semantical construct predicated upon observational experience. No news here. I'm sure FarSight gets this point. Heck, I think we all realized this point in our teenage years, its not really that deep.

I would make one distinction that may sound stupid and overphilosophical, but here it goes anyways... Human assign a number value to frequency, but frequency assigns a color value to our minds.

 

[Farsight]

Guys: I really want to draw your attention to this astonishing colour perception demonstration. Please do follow the link. It's a real gobsmacker, I couldn't believe it when I first saw it. But amazingly, it's true:

http://www.echalk.co.uk/amusements/OpticalIllusions/colourPerception/colourPerception.html

Q: When is blue yellow?
A: When they're both grey.

 

[zoobyshoe]

I might have the longer wave version of the long-wave cones.
In any event I can see when supposedly IR leds and lasers are opereating.
For example most remote controlers.
Exposed led ones are fairly easy to see. Some of the covered ones are barely (or not) detectable and the room lights needs to be dimed, but I don't have to wait for dark adaption.

You might contact someone who studies vision and offer yourself to be tested for this. It shouldn't be too difficult to design set ups to quantify the extent of your ability to do this.

I wonder how common this is.

Bigest thing I've noticed is that sometimes people will call red for what I would call a red/orange

In the case of pigments I only recently became aware that most of what passes for red in the medium of colored pencils is actually red-orange. There is a lot of yellow present that makes mixing purples from these alleged reds impossible. You end up with overly greyed results. The only really successful purples come from magenta and related shades, and not the "reds".

I could see the difference between "reds" and magentas before but now I am alert to the fact that the "reds" are actually richer red-oranges.

 

[DaveC426913]

In the case of pigments I only recently became aware that most of what passes for red in the medium of colored pencils is actually red-orange. There is a lot of yellow present that makes mixing purples from these alleged reds impossible. You end up with overly greyed results. The only really successful purples come from magenta and related shades, and not the "reds".

I could see the difference between "reds" and magentas before but now I am alert to the fact that the "reds" are actually richer red-oranges.

More generally, the reds you're using are "warm" reds (which means they have a lot of yellow). You should adhere to the guideline of mixing warm tones only with warm tones and cool tones only with cool tones. Crimson Lake and Cherry and related tones are cool reds and will mix well with your purples.

In fact, most artists tend to keep a warm and a cool of each colour on their palette.
Canary and lemon yellow are cool while school bus yellow is warm.
Azure is cool while sky blue is warm.
Forest green cool, lime green warm. etc.

 

[NoTime]

You might contact someone who studies vision and offer yourself to be tested for this. It shouldn't be too difficult to design set ups to quantify the extent of your ability to do this.

I was just curious to see if others could see their remotes light up.
Its easier if you turn the room lights off.
And try different ones, they vary quite a bit in brightness.
Or maybe it's just time to change the batteries

FWIW they look red.
The same color red as a visible red led.
It's the relative receptor activation that defines the color you see more than frequency.
All frequencies below the middle wave receptor activation point look red.

 

[zoobyshoe]

More generally, the reds you're using are "warm" reds (which means they have a lot of yellow). You should adhere to the guideline of mixing warm tones only with warm tones and cool tones only with cool tones.

I've only dabbled with paint, at this point anyway, and colored pencil designations are different, which makes crossover by color name problematic. The Prismacolor Crimson Lake was discontinued a long time ago, and they've never made a Cherry red. Everything now designated a "red" would be one of the "warm" reds you mentioned. For mixing purples what you have left are: Magenta, Process Red, Mulberry, and Raspberry pencils.

In fact, most artists tend to keep a warm and a cool of each colour on their palette.
Canary and lemon yellow are cool while school bus yellow is warm.
Azure is cool while sky blue is warm.
Forest green cool, lime green warm. etc.

That's something I can pay more attention to: whether or not a given pencil is cool or warm within the general cool or warm range it's in. I tend, naively, to treat all greens as cool, and so forth. In fact, I only recently started experimenting with mixing them since there is a huge range of straight out of the pencil colors of many different values to work with. I also only recently started muting colors by laying them on top of a bed of gray.

 

[DaveC426913]

I've only dabbled with paint, at this point anyway, and colored pencil designations are different, which makes crossover by color name problematic.

Well, these aren't paint colours, just colloquialisms. Crimson Lake is actually a Crayola colour.

I would think raspberry would be a cool red.

 

[zoobyshoe]

I was just curious to see if others could see their remotes light up.

No, I don't seem to have this experience.

You are InfraMan!

 

[DaveC426913]

So, I've posted https://www.physicsforums.com/showthread.php?t=134077" to see how many InfraPersons there are.