Science

The Science of Color, by Apryl

Art and Science Collide

 

To understand color, first we must understand how we see it. Our eye is much like a camera. It contains a lens that focuses the light, an iris (aperture) that controls how much light is let into the eye through the pupil, and the retina (the film or the image sensor). The retina lines the inside of the eye and receives the light that comes in through the pupil. It is made up of photosensitive cells called rods and cones. The cones are the cells that allow us to see color. Cones vary in their response to light, with over half responding most strongly to red light, a third responding most strongly to green, and a very small percentage responding most strongly to blue.

When light enters the eye, the retina and its combination of photosensitive cells detect the light waves which vary in length depending on the color. Information that the cells detect is then passed through the optic nerve to the brain, where it is then perceived as color.

With only three different types of color receptors, you may wonder how we can see such a wide range of colors! When light enters the eye, it will stimulate different receptors at the same time. All the colors we see are simply combinations of three primary colors. For example, if you see magenta, then the lightwaves are stimulating red and blue receptors, but not green. When all of the cones are stimulated equally, we perceive white.

How do light waves mix to form colors? Light is made of waves of energy that are grouped together in a spectrum. Our eyes can only see a portion of the light spectrum. At the shorter end of the visible spectrum, the light waves are perceived as blue. At the longer end of the visible spectrum the light waves are perceived as red. Green is in the middle, and all other colors we perceive fall in between. Light waves that fall outside of the visible spectrum are not visible by the naked eye, but may become visible with aids such as night vision goggles or x-ray machines.

When mixing colored light, you are essentially starting with darkness, or the absence of light, and then adding in light that falls along the visible spectrum. For example, green light plus blue light gives you cyan. All three primary colors of light mixed together will give you white. This is called the additive color system, and this is how all image capture devices (such as cameras, video, etc.) handle color.

When creating artwork, it is important to know how the light spectrum works, and how the additive color system used in controlling light color differs from the subtractive color system that is used in mixing pigments for paint and ink.

Objects, photographs, and artwork all express color by absorbing some light wavelengths and reflecting back others. For example, a white sheet of paper appears white because it is reflecting back the entire visible spectrum of light waves. A sheet of black paper appears black because it is absorbing the entire spectrum. To illustrate the example further, picture a white sheet of paper. It is currently reflecting back all the light waves. When you add a circle of cyan paint, it subtracts the cyan light wave from what it is reflecting back to you, essentially absorbing the cyan light wave. The eye perceives this and interprets it as a cyan colored dot. If you layer a yellow dot directly over the cyan dot, it is subtracting cyan and yellow from the light waves that are reflected, and your eye perceives green. In theory, overlaying the three primary pigments cyan, yellow and magenta would absorb the entire spectrum of light waves and you would perceive black.

Often, when mixing paints, the colors are not pure and the results are muddy. This is why when mixing paints or inks, pure pigments are needed to get accurate results. Also, since light itself is color, your light source will change how different paints and inks are perceived.

Try your hand at mixing colors in this virtual color mixing lab:  http://sciencenetlinks.com/tools/mixing-primary-colors/

Here is a beautifully designed App from the Exploratorium called Color Uncovered  https://www.exploratorium.edu/explore/apps/color-uncovered

References:

O’Haver, T. (2001, January). In Living Color. Retrieved February 19, 2014, from Inform.umd: http://www.inform.umd.edu/MCTP/Courses/ColorLesson/

Pappas, S. (2010, April 29). How Do We See in Color. Retrieved February 19, 2014, from livescience: http://www.livescience.com/32559-why-do-we-see-in-color.html

unknown. (n.d.). Understanding Color. Retrieved from RGB World: http://www.rgbworld.com/color.html

Apryl–Born and raised in Tennessee, Apryl is a southern girl at heart.  She lives out in the country aprylwith her husband and her three daughters. After having an unfulfilling public school education herself, and struggling to find peace with the education her girls were receiving in the public school system, she made the choice to homeschool.  When they began their homeschool journey, the girls were in the third and sixth grades.  Now she is happily coaching three teenaged daughters through their high school years.

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