[trader]

Is it correct to say that ( approximately ) 55.133 total percent of the red is reflected back from the USA executive flag, but of this 55.133 quantity only 41.5 percent quantity is visible to the eye as the color red and the other 13.633 is hidden and mixed with other colors that together appear white to the eye ? Is this statement another way to correctly state what you said above or am I still missing something very important ?

[Peter Ansoff]

Is it correct to say that ( approximately ) 55.133 total percent of the red is reflected back from the USA executive flag, but of this 55.133 quantity only 41.5 percent quantity is visible to the eye as the color red and the other 13.633 is hidden and mixed with other colors that together appear white to the eye ?

No, it's not correct. I'll try to explain why -- I'm definitely not an expert in optical physics, and someone who is may be able to explain it better. Anyway . . .

There are around 300 (I think) wavelengths in the visible light spectrum that the eye can perceive as distinct colors. Three of those wavelengths are designated as "pure" red, blue and green. This is because the human eye contains three different types of light receptors, each of which is sensitive to one of those three particular wavelengths. If a light beam of light happens to contain one of those three wavelengths (red, for example), only the red receptors are stimulated.

In the real word, of course, most of the light that hits our eyes is not one of those three particular wavelengths. In those cases, more than one set of receptors is stimulated. For example, yellow light will stimulate both the red and the green receptors. The degree of stimulation of each set will depend on the "mix" of the color -- if the particular wavelength of the yellow is more toward the green side of the spectrum, the green receptors will be stimulated more than the red receptors. (The brain, of course, interprets this as the appropriate shade of yellow.) If the light is white, all three sets will be equally stimulated.

The point is that when you try to add the red reflected from the red stripes of the flag, and the red component of the white, you are mixing apples and oranges, so to speak. In the first case, you're talking about the particular wavelength of light that is reflected by the stripes, and in the other about the proportion of the white light that stimulates the red receptors in the eye. The red reflected from the red stripes is not "pure" red -- it actually has a substantial blue component, and looks almost purple under some conditions. (The red in the Canadian flag, for example, is closer to the "pure" red). If you really want to analyze the proportions of the three primary color wavelengths that are reflected from the flag under white light, you can do that, but the problem is considerably more complex.

Once again, I really don't see the point of all this. When you make a flag, you start with white fabric and dye the appropriate sections in their respective colors. The quantity of dye (or of dyed cloth, if it's a sewn flag), is driven by the proportion of the surface area that reflects each of the three colors. The physics of how the eye perceives color is a separate issue.

Peter Ansoff

[Robin Hickman]

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Why, Yes, now that you've asked me, I actually DO happen to think that this thread should be "closed" !!!

Robin Hickman
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