The Reverse of how colors work: how would it look?

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WorldTradeRichard
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The Reverse of how colors work: how would it look?

Postby WorldTradeRichard » Sat Mar 18, 2017 5:42 pm UTC

It's a simple question:
Image

Upon looking at this drawing, I began to wonder what the object in Our universe (colored red when it absorbs all wavelengths of visible light except for red), would look like instead if it absorbed ONLY red and reflected all other colors, like an opposite. Moreover, what would an object look like if it's color was a solid "all colors except for red"? Does it just blend?

I understand slightly the answer, but I can't really put it into words and I have to explain it to a Younger one.
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Sizik
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Re: The Reverse of how colors work: how would it look?

Postby Sizik » Sat Mar 18, 2017 5:58 pm UTC

If it absorbed red and reflected all other colors, it would look cyan.
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Re: The Reverse of how colors work: how would it look?

Postby Soupspoon » Sat Mar 18, 2017 5:58 pm UTC

In the setup you have above, assuming specific red rays, green rays and DVDs blue rays, a red-absorbing object would reflect green and blue, which would result it in being seen as cyan.

But that assumes a rather specific lighting. Natural lighting is a spread of frequencies, with gaps that you don't notice unless you're looking for them. i.e. an object that was 'red' in that it absorbed only the red light at (say) 680nm, though, does it not absorb light at 640nm (still red)? 660nm (a closer red)? 670nm? 679nm? Given a white light source, the narrower the absorption, the more red-but-not-exactly-as-red light there is that still reflects to work with the reflected non-reds to appear "white" (or nearly so) to the Mark I Eyeball.

See https://en.wikipedia.org/wiki/RGB_color ... n_and_blue for the whole "why RGB"/vision thing...

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Eebster the Great
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Re: The Reverse of how colors work: how would it look?

Postby Eebster the Great » Mon Mar 20, 2017 2:24 am UTC

The "red object" in your drawing looks magenta to me.

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Re: The Reverse of how colors work: how would it look?

Postby Xanthir » Tue Mar 28, 2017 6:09 pm UTC

Note that this "absorbs one color and reflects everything else" is the way that *most* objects in the real world operate. Reflecting only one color is relatively rare - that's a lot of energy to absorb, and molecules usually only have a small band of wavelengths they can absorb, so you need either a very good mix of molecules covering the absorption spectrum, or some very special molecules that have extra-wide absorption bands (like that hyper-black coating that's making the news rounds again).

For example, apples are red because they absorb greenish light and reflect everything else.
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