What is color and where is it?

1. Newton, or it is just physics

So what is color and where is it? Seems like an easy question, right?

We probably all learned about Newton’s experiment crucis, a series of experiments, where he was splitting sunlight with prisms. Yes he did those experiments during a plague year in England…

Newton’s experimentum crucis concluded that sunlight can be separated in its colored wavelength with a prism through refraction. Those colored beams can not be separated further with another prism refracting the light, or in any other way. The colors can only be changed by mixing them with each other or other colors. So they are the most basic components of color, often called monochromatic colors or spectral colors.

The monochromatic colors are the colors of the rainbow, each wavelength in the visible spectrum is a pure hue ranging from violett, blue, green, yellow, orange to red. They are the most pure and saturated colors we can see. Those colors are basically forming the boundaries of all the visible colors for us.

Newton published his conclusions in his book “Opticks”, one of the seminal works on color in color theory.

Besides all those experiments, Newton did one other really important thing for us artists, he created the first color circle / color wheel, by connecting the red and blue end of the spectrum. This is the earliest organization of color, two dimensional here, the color circle is used in one version or another in every graphics software today.

Seeing Newton’s experiments the first part of what is color, is: color is in light, without light there is no color.

Probably worth asking what is light in that case, right?. So let’s do a quick side step to look into that.  

2. Interlude, what is light?

Light is electromagnetic radiation in the spectrum humans can see, also called the visible spectrum. If we can't see it, it is not light.
Light is the reason we see the world around us and the reason we can see color.

There is a famous Einstein quote I do really like, "For the rest of my life I want to study light.".
I think that was while he was working on his theory of relativity, but I might be wrong. We as artists have to study light as well, to create good comps, renderings or paintings and I do like that the quote shows that there is a connection between scientists and artists. Often either art or science are influencing each other to advance both fields. Anyway back to the topic...

As you can see in the graphic below, the visible spectrum is quite a narrow band in the electromagnetic spectrum, between 380nm and 780nm wavelength.

Left of the visible spectrum are the shorter wavelengths like ultraviolet radiation, on the right end are longer wavelengths, infrared, microwaves and radio waves.
You can also see the monochromatic colors for each wavelength range, as Newton specified them in his experiments (minus the Indigo which was more a blue). ROYGBIV is a common abbreviation to remember those colors and their order.

The wavelength for the monochromatic colors are:
Red at wavelengths higher than 630nm.
Orange is at wavelengths 590nm-630nm.
Yellow is at wavelengths 560nm-590nm.
Green is at wavelengths 480nm-560nm.
Blue is at wavelengths around 480nm.
Violet is at wavelengths shorter than 450nm.

Radiometry and photometry are the two sciences measuring light, radiometry measuring it in the full electromagnetic spectrum including the visible spectrum, photometry measuring it only in the visible spectrum.
I might write a little more about those later, since they are helpful to understand light measurements and scene linear workflows.

Of course there is more to light but for the sake of color that is good enough, back to a little more history.

3. Goethe, or don't forget the human

When Newton published his “Opticks”, not everybody was fully on board with his conclusions and especially the "lazy" way some of his peers interpreted his findings.
One of his critics was Johann Wolfgang von Goethe, the famous German “Dichter und Denker”. I am sure many Germans have painful memories of having to read his Faust in school, I certainly do, but to go back to the “Pudels Kern”...

Goethe was curious enough to borrow prisms, which were very expensive at that time, to replicate all of Newton’s experiments. I do find that very impressive, and honestly the best way to make sure things are what they are and you do understand them correctly is to try them for yourself. It just needs some prisms and C-Stands (not sure where Newton or Goethe got those from) and most of Newton's experiments can be replicated more or less easily.

After doing all the experiments himself, Goethe criticized some of Newton’s findings and added his own insights, publishing a book about it all, because why not. That is the second seminal work in color theory, Goethe’s “Zur Farbenlehre”.
To keep it short here, Goethe’s main point in Zur Farbenlehre was, color is in light, sure, but Newton completely forgot the human experience and interpretation of it. So there is the human factor to the whole color experience which we can not ignore if we want to describe or specify color. It is not only physics it is also psychophysics, our experience and perception of color.

He did a surprising amount of color observations and experiments and describes things like afterimages, complementary color experiments and his “Kantenfarben” in this book. Really cool stuff in there, it did show me that you need to be a good observer to be a good artist and it clearly shows how curious and versatile Goethe was.

Oh and of course Goethe did create his own color wheel, that thing really started to become popular. 

As you might have noticed Goethe organized the colors in his color wheel with complementary colors opposite to each other. He also assigned qualities to each color, yellow is good, green is useful, blue is mean and so on.

Summary, what is color?
Color is a combination of different things, color is in light and color is a human sensation, it depends on psychological phenomena and on our vision.

Which leaves us with two of the three main components in color science, light and the observer (us), the third is objects / materials. I am gonna write about color in nature next and  follow up with human vision, the observer, right after that.
From there we can check how we were able to describe color with math, which at the end is what we need to put it into computer models.

As always let me know if you have questions, critique or input please, hello@christophschroeer.com.