I My 50 year old Science book says that Black is the absence of all color

[gary350]

TL;DR Summary

Do any books still say, black is absence of all color?

My 50 year old science book says, black is absence of all color. Do any books still say, black is absence of all color?

I looked online for 30 minutes no where say, black is absence of all color. NOW everything says, Black is the darkest color.

Why the change in books? If black is not a color then how can it be the darkest color?

 

[berkeman]

Summary:: Do any books still say, black is absence of all color?

My 50 year old science book says, black is absence of all color. Do any books still say, black is absence of all color?

I looked online for 30 minutes no where say, black is absence of all color. NOW everything says, Black is the darkest color.

Why the change in books? If black is not a color then how can it be the darkest color?

What color is outside of the additive color triad?

https://en.wikipedia.org/wiki/Additive_color

What color is in the middle of the subtractive color triad?

https://en.wikipedia.org/wiki/Subtractive_color

Spoiler

 

[sophiecentaur]

Summary:: Do any books still say, black is absence of all color?

My 50 year old science book says, black is absence of all color.

That makes no sense and it didn't then, either. Britannica used to get a lot of Science horribly wrong at one time. Likewise elementary textbooks (all subjects) at times. Nothing about colourimetry has actually changed significantly in the past hundred years. The details of the topic are still on the move , though.

Black is the absence of any light. And colorimetry has been studied for much longer than 50 years. The Tristimulus approach to colour vision works on the principle that we analyse the colour that we see in terms of three wideband colour filters (the reds, the blues and the greens in the middle) and it is the sum of the three 'signals' that tells us the brightness and the ratios that tells us the colour. With black, there is no light so we cannot assign a colour. In fact our low level vision has no colour discrimination ('rods') and we need higher levels of light to perceive colour ('cones'). (Rods and cones are the different types of sensors on the retina.) See this link.
But colour is essentially a subjective thing and different individuals will have different versions of what they see - although we all learn and agree what to call colours that are in the red regions and the greens, browns, purples etc.
Other theories exist about colour vision but the basic tristimulus system does a pretty good job for colour TV displays and we mostly tend to agree about the colours that TV reproduces - but not everyone. There are some odd questions asked by some people as to whether the red I see could be the blue that you see but that's largely just 'idle fancies'. We see a leaf and I call it green and you may call it vert - but that's just language

 

[hmmm27]

If you say "Well, my sweater is red, my pants are blue, and my socks exhibit no radiative properties in the visual spectrum", people will look at you funny.

That's pretty much it. What's the confusion ?

 

[SchroedingersLion]

That makes no sense and it didn't then, either. Britannica used to get a lot of Science horribly wrong at one time. Likewise elementary textbooks (all subjects) at times. Nothing about colourimetry has actually changed significantly in the past hundred years. The details of the topic are still on the move , though.

Black is the absence of any light. And colorimetry has been studied for much longer than 50 years. The Tristimulus approach to colour vision works on the principle that we analyse the colour that we see in terms of three wideband colour filters (the reds, the blues and the greens in the middle) and it is the sum of the three 'signals' that tells us the brightness and the ratios that tells us the colour. With black, there is no light so we cannot assign a colour. In fact our low level vision has no colour discrimination ('rods') and we need higher levels of light to perceive colour ('cones'). (Rods and cones are the different types of sensors on the retina.) See this link.
But colour is essentially a subjective thing and different individuals will have different versions of what they see - although we all learn and agree what to call colours that are in the red regions and the greens, browns, purples etc.
Other theories exist about colour vision but the basic tristimulus system does a pretty good job for colour TV displays and we mostly tend to agree about the colours that TV reproduces - but not everyone. There are some odd questions asked by some people as to whether the red I see could be the blue that you see but that's largely just 'idle fancies'. We see a leaf and I call it green and you may call it vert - but that's just language

You say it makes no sense, but your explanation is completely equivalent to the statement that "black is the absence of all colour", isn't it? Identifying colours with certain wavelengths, the absence of colour is the same as the absence of light.

 

[sophiecentaur]

You say it makes no sense, but your explanation is completely equivalent to the statement that "black is the absence of all colour", isn't it?

Black is the absence of all light. Whatever the colour of the light happened to be when it was turned off is, africa, irrelevant. If you were being really fussy then you could say that, as colour can be described as a ratio of different analysis primaries and black involves all the factors being zero, it's ill conditioned.

Does this thread really need to go on for any longer? It could be a solution to my insomnia as there's no Physics in it.

 

[SchroedingersLion]

Black is the absence of all light. Whatever the colour of the light happened to be when it was turned off is, africa, irrelevant. If you were being really fussy then you could say that, as colour can be described as a ratio of different analysis primaries and black involves all the factors being zero, it's ill conditioned.

I was just curious why you would reject the statement with "no colour" that much, because they are equivalent.
No light => no colour.
No colour => no light.
Therefore, "black is the absence of all colour" <=> "black is the absence of all light".

 

[hutchphd]

I will ask a slight variation, then. What defines a 50% gray?

 

[sophiecentaur]

I will ask a slight variation, then. What defines a 50% gray?

Haha. May I remind you that nobody likes a smarty pants.
The ratios are all unity because there are actual values for RG and B. So grey (Same as white) is an actual colour. Tadahh!

 

[Merlin3189]

No idea what defines 50% gray, but maybe it reflects (diffusely) 50% of the white light falling on it? But Wikipedia tells me, that's about the albedo of old snow or alto cirrus cloud, which I guess most of us would call white?
I'm struggling to find any decent values to quote, as Google seems to think the only things we want to know the albedo of are planet surfaces, especially earth. But I've seen values of 80-85% for white painted surfaces and 20% for dark painted surfaces.
I have a very hazy memory of my visual perception prof saying that a "blackboard"* could reflect as much as 50%, equal to what I'm saying you mean by 50% grey. (* probably called a chalkboard or something now.)
He of course knew that absolute values are pretty meningless in visual perception. Context is everything. Depending on lighting, surroundings, what other surfaces are adjacent, not too mention your previous experience and knowledge of conventional descriptions, one physical object may appear to have a range of colours and brightness.

Back to the original question. I too would have said black was the absence of light, which obviously implies the lack of colour.
But then I remembered we used to call UV, "black light". I'm not sure whether UV counts as a colour - at least far enough in as to not register with our eyes. But does it count as light?

BTW I think you can get π angels dancing on the head of a pin, but I wonder what Sophie thinks?

 

[sophiecentaur]

50% of the white light falling on it?

White has no unique definition. The CIE chromaticity diagram has a number of defined 'illuminants', specified by temperature of a black body. Once you choose your illuminant (and your three primaries) then all the other colours will have unique RGB values. So a grey is actually defined in terms of the illuminant.
Black, otoh is what you get when you turn all illuminants off. All blacks are the same. All greys are not (even allowing for the % luminance value).
This box is empty, so is this box and this box but they all have different sorts of emptiness. If they are 'half full' then they are half full of something.
This thread has become suitable for pub conversation after lockdown.

 

[gmax137]

Medium, between white and black is "18%" grey. There is some kind of logarithmic thing, if I recall.

Also, 18% grey is the normal color of the sky in Rochester NY.

 

[hutchphd]

For my money the "science" of color is fraught with ambiguities and I avoid it. And yet I have designed two color meters. I always want to see a spectrum.

The questions of white black or more generally gray are not really nebulous at all. One usually is talking about diffuse reflectance of light energy (Remission) from a thick layer of pigment. To be uniformly gray this reflectance must not depend upon wavelength. The gray value can vary from 0% Remission (which we call black) to 100% (which we call white) at all viable wavelengths. Does not depend upon illumination.

The transmissive analog of gray is a "neutral density" filter usually characterized logarithmically by an optical density. Again does not depend upon illumination.

Of course our calibration in either case requires a known fixed value for comparison (the moon is 12%!).

Anything else, absent an illuminant spectrum and a target spectrum, is beyond what I choose to worry about. Angels indeed!

 

[A.T.]

I was just curious why you would reject the statement with "no colour" that much, because they are equivalent.
No light => no colour.
No colour => no light.
Therefore, "black is the absence of all colour" <=> "black is the absence of all light".

Just because something is not wrong, doesn't make it a good definition. Describing the lack of something (light) as the lack of a certain property of that something (color of light) is unnecessarily indirect.

 

[sophiecentaur]

I was thinking further. Our colour perception fails in low light conditions. So, not as a Scientist, perhaps, one could say black (and low luminance conditions) could be said to be without (perceptible) colour.

 

[gary350]

If you say "Well, my sweater is red, my pants are blue, and my socks exhibit no radiative properties in the visual spectrum", people will look at you funny.

That's pretty much it. What's the confusion ?

Black is not a color but black is the darkest color.

 

[hmmm27]

Black is not a color but black is the darkest color.

In your one sentence you've used two slightly different definitions of "color" (notwithstanding you've spelt it wrong... "colour" ) . This is not actually a physics issue : there, you're looking at wavelength and frequency.

I'd happily postulate that the former is part of an introduction to optics (rainbows, etc), the latter an approach using dyed clothing, or painting as a context.[edit: or LCD monitors where the dye blocks the backlight]

Perhaps in the intervening half a century the blurb on "what is colour" was shifted around a bit in the general curriculum... or just plain old dumbed down.

The actual physics context for "black" is "black hole" (where it makes sense) and "black body" (not so much).

 

[sophiecentaur]

This is not actually a physics issue : there, you're looking at wavelength and frequency.

It is very rare to be looking at a single wavelength source (except in a lab). Colour perception (spelled with a u, of course) nearly always involves analysing and recognising a continuum of wavelengths. There are methods of reproducing colours with remarkable accuracy (people cannot usually tell the difference when it's been done well).

Perhaps in the intervening half a century the blurb on "what is colour" was shifted around a bit in the general curriculum... or just plain old dumbed down.

It's different now but not necessarily worse. A lot of people use cameras and image processing and they have a far better idea about what's going on than the general public did, fifty years ago. It's probably one of those topics that has actually been the reverse of 'dumbed down'.

 

[gary350]

OK books use to say, black is Absence of all color. Then I read, Black is not a color AND black is the darkest color. WHY has it changed? With all the crap going on these days I wonder if someone is trying to be more political correct with the word BLACK.

 

[sophiecentaur]

WHY has it changed?

Has it really changed? The only remaining evidence of the opinions of the 60s is in textbooks. I seem to remember having similar, open conversations about colour which were about as lacking in Physics as they are these days.
I also remember the pointless discussions about the 'upside down' image on the retina, as if it were the slightest bit relevant to our vision. Any animal using a lens for vision will have had the software already built into take care of that since the first 'eye' was evolved. The psychology of the way we deal with our input signals is far too complex to try to boil it down to simple 'text book' statements.

 

[A.T.]

WHY has it changed?

It is just used differently, in different context, just like many other words.

 

[gary350]

It is just used differently, in different context, just like many other words.

This reminds me what my aunt use to say. She became a nurse at the start of WWII and was a nurse for 40 years. When people were sick at their stomach they, threw up. Every few years management decided we need a nicer word so they started saying, vomit, then, puke, then whale, barf, hurl, up chuck, purge, spew, fetch up, throw up. I never liked, up chuck, once I was in the hospital nurse ask me if I was going to, up chuck, I said, NO I never do that I, "PUKE". You should have seen look at that nurses face it was so funny. LOL

 

[hmmm27]

OK books use to say, black is Absence of all color. Then I read, Black is not a color AND black is the darkest color. WHY has it changed? With all the crap going on these days I wonder if someone is trying to be more political correct with the word BLACK.

Maybe ; what's your theory ?