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

[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.

 

[zoobyshoe]

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

Well, it's a mixed bag. Some colors are named for the source they're derived from:

"lake
1 a : a purplish red pigment prepared from lac or cochineal b : any of numerous usually bright translucent organic pigments composed essentially of a soluble dye absorbed on or combined with an inorganic carrier"

and others are invented labels for a hue that might be mixed from who knows what different sources.

I expect zinc white to contain zinc oxide and be consistant across manufacturers. The same for yellow ochre and its derivatives, cobalt blue, cadmium red, etc.

"Raspberry" and "Limepeel", I don't expect to be made from fruit, and am not surprised if there's an inconsistancy between two different manufacturers who both use these names for something.

 

[DaveC426913]

You might be interested in a book called https://www.amazon.com/dp/0812971426/?tag=pfamazon01-20. The author travels the world to explore the origin of colours, from the white clays in Australia to the red cochineal bugs of Brazil.

 

[zoobyshoe]

You might be interested in a book called https://www.amazon.com/dp/0812971426/?tag=pfamazon01-20. The author travels the world to explore the origin of colours, from the white clays in Australia to the red cochineal bugs of Brazil.

Sounds like exactly the kind of book that would interest me just now.

Send it to:

Mr. Z. Shoe
Zoobie Brush Shelter
Tecolote Canyon
San Diego, Ca.

 

[LHarriger]

Technically, the only necessary condition of black is "no light is emitted from it."

Why must light not be emitted?
Consider a thin film such as a bubble. The bubble does reflect light back, but undergoes a 180 phase change when reflecting off the inner surface while rays on the outer surface do not experience a phase change at all. The thinnest part of the bubble does not provide ample path length difference between waves and as a result the waves cancel causing black. So it seems to me that it is safe to say waves can leave from a substance in the direction of your eye and still result in black or am I missing something? Does the fact that their superposition results in zero truly cause the waves to no longer exist?

 

[thiotimoline]

Ok if most people say that black is an absence of colour, then is black a colour? In addition, if some light comes back to our eyes and we perceive it as a colour, then by the definition of black, no light comes back to us, hence there is no colour. By saying this, does that mean than an absence of colour = transparent?

 

[zoobyshoe]

Ok if most people say that black is an absence of colour, then is black a colour? In addition, if some light comes back to our eyes and we perceive it as a colour, then by the definition of black, no light comes back to us, hence there is no colour. By saying this, does that mean than an absence of colour = transparent?

The notion of black as a color preceeded the scientific understanding of the cause of the phenomenon of color by tens of thousands of years. It arises from the nomenclature for pigments. Primitive man, for instance, smeared himself with soot and charcoal in preparation for rituals and the color of it had specific meaning. The color had to be named to distinguish it from the white china clay he might use on a different occasion or the yellow ochre he might use on another.

We can call black a color because it's part and parcel of the in-place nomenclature for pigments.

A lady goes into a fabric store and hands the clerk a list of "colors" she needs: red, orange, black. She's making a halloween costume. Black is tacitly accepted as a proper color, no one gets upset, no one has been harmed.

Although it's nice to understand that the phenomenon of black results from the absense of the EM waves that cause the other colors, the notion of banging your head against the wall wondering if it's still proper to refer to it as a color is an obvious waste of time.

 

[arjijon]

how do you define colours?

 

[Big Bill]

No, it is still just the absence of color. If it absorbs all radiation, then it doesn't reflect any to your eyes and your eyes see nothing.

Absence of reflected light then, surely. That which does not reflect the light may be described as black. Black can have many meanings, though. Is it a wave or a particle or both? Black is certainly a colour in loose parlance, but perhaps not strictly speaking. I go for the manifestation of the absence of reflected light.

BB

 

[Ironman Joe]

If you add black to a "colour" you will change that colour. If black were not a colour, how could it change a colour? It is a matter of reflection. Black doesn't reflect any light WE can see. There are, for example, insects that can see colours we can't. Just because we can't see it, doesn't mean it's not a colour. Think about it, the only time we can't see black is when everything around a black object is black, add the tiniest bit of reflection to the surroundings, and the black object becomes visible. It's a colour, get over it.

 

[DaveC426913]

If you add black to a "colour" you will change that colour. If black were not a colour, how could it change a colour?

1] If we're talking about pigments, then most poeple agree that black is a colour. But not because of your argument. By your argument, water is a colour, since adding water to a colour, will get you a different colour too.

2] If we're not talking about pigments, and we are talking about light from an illuminated source, please demonstrate how you will (and I quote) "add black". I am not aware of any lights that emit light that is black. Are you?

It's a colour, get over it.

Don't be snotty.

 

[Ironman Joe]

Not trying to be snotty, just looking for a laugh. No there is no such thing as black light, unless your a hippy from the 60s. Space is not black, because any light continues until it strikes something reflective, it's transparent. Black holes are truly black, bacause light that strikes them just turns into matter on the surface. Shine a light on a black object, and you will see it. Shine a light on a black hole, which is still an object, you still won't see it. Black as a pigment is a color, in the realm of illumination, it does not exist.

 

[lotrgreengrapes7926]

This reminds me of the debate of Pluto's...planethood.
The only reasons you would see a black object are
1) it's not truly black and reflects some light,
2) you "see" it because it is different from its surroundings.
If you were in a sealed room, painted totally black, and you shined a flash light against a wall, you would still see nothing (except for maybe reflection of dust in the air).

 

[DaveC426913]

This reminds me of the debate of Pluto's...planethood.
The only reasons you would see a black object are
1) it's not truly black and reflects some light,
2) you "see" it because it is different from its surroundings.
If you were in a sealed room, painted totally black, and you shined a flash light against a wall, you would still see nothing (except for maybe reflection of dust in the air).

I find it interesting that I could paint that room six thousand different kinds of red and we'd still call it red. But that is not true of painting it black. If you pick up any light from it at all, you'll tell me what colour has been added to the black.

The colour "red" (or "green" or whatever) can have a nigh-infinite variety to them, yet this "black" has only a single flavour.

If black is merely a colour like every other colour, why does it follow rules so stringent as to be impossible to execute in real life?

That seems suspicious to me in terms of whether we can call it a colour, even in pigments. It seems to be more of an ideal concept.

 

[leemuhammad]

Black is the opposite of color, you must have light to have color. All colors come from Black.

 

[disregardthat]

All colors come from black?

The way we understand black is the absence of it. When we read the words here at the forum, we don't actually see them, we anly see the absence of light, which form letters in our head. I have read many stupid things here, but I must say I agree most with zoobyshoe.

I have not read the whole topic, but the one who said oxygen is black, has got it all wrong. We see an object as black if it absorbs the light with wavelengths we can see, and does not emit any light in the frequenzies we can see. Oxygen does not ABSORB any of the light in the frequenzies, (if it does it must be minimal, because we can't see the absence of any color), the light that we can see, goes through them. It doesn't get the right amount of energy to "knock" the electrons to a higher level to emit electromagnetic radiation. That's why we see them as transparent.

I may have expalined myself a bit flawfully, but the reason of that is that I can't find words for everything i mean.