Subject Reality

Consider our experience of the color green. In the physical world there is light of a certain frequency, but the light itself is not green. Nor are the electrical impulses that are transmitted from the eye to the brain. No color exists there. The green we see is a quality appearing in the mind in response to this frequency of light. It exists only as a subjective experience in the mind.

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Green is identified by a set of light frequencies; the fact that it is a qualitative does not mean that light in the green range is any less green. Also, the colour receptors in our eyes respond to different frequencies, so green light triggers certain receptors that allow us to experience green rather than another colour.

Green is defined by frequency range; that frequency range might be slightly different depending on the conventions of the people using the language. In other words, 'green' might refer to a slightly different range of frequencies to brits, aussies, and yanks - but thats the basic issue of 'semantics', not an issue of subjective perception.

Aquilinas is right.

I'm slightly color blind, so no color is really the color one says it is.

Actually, light is not green. You cannot see green in light unless you shine regular (white) light through a prism or green filter.

The color green in a object is seen because of pigments that reflect and absorb light. The pigment that we see as green actually reflects the frequency of yellow and blue and absorbs the frequency of red. Yellow and blue together create what we see as and call green.

Aquilinas is incorrect and so are you.

Color is subjective because it is Dependant upon our receptors and our ability to see color which is the mind at work.

Conditions of the light and filters also effect color. A green cloth under a red light just looks brown. As long as there is only red light (perhaps shining through a red filter of some kind, or a red atmosphere) the cloth will always appear brown under a red light.

If conditions of the light change and the cloth suddenly looks green, a person who has only seen it as brown might say, "that brown cloth looks green under these conditions."

So color is subject to conditions of light, and to our receptors in our brain.

A 'green' cloth under a red light...

A but you see a cloth under a red light has its frequency modified by the environment...

therefore you can not label the cloth green.

'green' as a pure color can only exist under the proper ambient frequency range.

if the frequncy range is modified then the cloth 'becomes' the 'color' assigned to the frequency it reflects.

No, the 'green' cloth does not have its frequency modified at all.
The only thing modified is the light.

The cloth is only labeled "green" because under "normal" light, that is what an observer would see. But.. If the observer NEVER saw the cloth under normal light, you are right, then he would have no way of knowing that the cloth's color was green and he would not label the cloth "green" nor would he paint it "green" if he were an artist.

Totage,

Good example. Consider a world where everyone was color blind. Then a person enters the world who is not color blind. Imagine all these color blind people were painting pictures of how they see things. Now picture what these picture might look like to the person who is not color blind. They would probably look very strange.

Color is basically a refelection of light, and we all see things different. Your green, may be my blue. We learned to call we we saw as green, green and what we saw as blue, blue, even though to someone else our blue may be their green, and our green may be their blue. That's why when I tell people I'm color blind and they try to point out colors, I can get them right, it's the shades that get me.

Its true that green is seen in an object because of the interaction of the object and light - but there is also such a thing as 'green light'. When you see the color green, you are actually seeing green light that has reached your eyes.

Also, we can create green light directly using diodes.




You are not talking about color, you are talking about our experience of color. Why choose terms to be meaningless and vague? Scientists often have the good sense to choose their definitions deliberately and intelligently, aiding them in their exploration and discussion of truth. Theirs is an excellent approach.

You keep saying "color" when you really mean "our internal, separate, subjective experience of color". Naturally our subjective experience of color is subjective.



You've labelled the cloth 'green' only because it reflects a great deal of green light when subject to white light.

Naturally a cloth that reflects very little red light is going to reflect very little light (and appear brown) when illuminated with a red light.



All true, and it doesn't change the fact that color (which is the frequency range of light) is objectively measurable.



No, the color of the light reflected by an object is subject to the conditions of the illuminating light - which is obvious. Whichever color of light is so reflected is still objectively definable and measurable.



Yes, exactly. And it all seems to me to be mostly unrelated to the fact that color itself is objectively definable and measurable.

I think what is being measured is light frequency, not color.

I personally have never "seen" green light unless it was light shining through a green filter or glass or prism or in a rainbow which is a prism.

If there are no pigments on an object you would not see the color.

So please tell me how you can see actual green light?

Sure, light plays a roll in everything we see, but normal light has no color.

What is a diode and how does that work?

Yep. The alternative is too much of a mouth full of words.




Exactly. And it is what we normally and simply call "color."

Color is actually just light.

Much of this conversation is simply an argument about semantics.
What is being measured is light frequency, which is color.




When you see white light, you are seeing green light - you are just not equipped to directly sense that green light is a part of the white light that you are seeing. If the light did not have green in it, it would not appear white.




After appropriately colored light interacts with appropriately pigmented object, the light that leaves the object might be dominated by frequencies in the range that we term 'green'. When this light strikes you retina, you are not only 'seeing green light' in the same sense that you see green light when white light strikes your retina, for non-color-blind people we also sense that green-frequencies are dominating the frequency distribution of the light.



What is 'normal' light? The sunlight that reaches the earths surfaces is biased towards yellow, many indoor lamps are biased towards yellow and some are biased towards blue. I think its actually just a little inconvenient to produce a nice pure white light that isn't biased towards any colors - and is rarely desirable.



That may be what you normally call color, but not me nor most of the people I have serious conversations with on a regular basis.



The technology behind diodes is vaguely similar to that behind solar panels and computer chips - in that two differently doped regions of a material are in close proximity, creating a unique situation at the junction. I've forgotten the details, but the point is that this allows us to create a very pure light, with a very narrow frequency range.

I believe (could be wrong) that neon bulbs also allow us to directly create light in a narrow frequency range.

Most of the ways that humans created light before the modern era relied on heating something - and hot objects naturally emit light on a range of frequencies, not a narrowly defined frequency. The normal way to create light of a pure color was to produce broad-spectrum light and send it through a filter.



Cool! Another point of agreement between us.

I'm glad we agree.


Green is not green, it is just light. LOL

"It's not easy being green"

Yeh, just ask Kermit the frog.

A diode is simply a semiconductor that allows electricity to pass in one direction, but not the reverse.

A light emitting diode (LED) is basically the same thing but converts some of the electrical energy into light over a relatively narrow frequency band. This device is similar to a resister which reduces voltage by converting some of the electrical energy into light in the "heat" bandwidth of infrared.

A similar solid state device would be the maser where microwave radiation (a form of invisible light) is created at a single frequency by the stimulated emission of radiation.

And finally there is the laser where, using solid state devices or encapsulated gas, light is created of a single frequency by the stimulated emission of radiation. Some of these devices are "tuneable" allowing the precise frequency to be selected.