Color Perception

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Biology 103
2001 Second Web Report
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Color Perception

Sana Dada

"Color is a paradox. It exists only in light, which to the human eye seems almost colorless. Without light there can be no color (1)." If this statement is true, then how does then how it is possible to see such a diversity of colors in nature, and how do we, as humans achieve numerous effects by color? To the answer this question we have to understand major elements. They are light, which is the source of color; the object and how it reacts and responds to color; and the eye which is the perceiver of color (1).

The electromagnetic spectrum consists of many different sources of energies, which have different wavelengths. One of these sources is visible light. Visible light is the only part of the spectrum that the human eye can see. The wavelength of light ranges from 380 nm to 750 nm. Color is our response to the stimulation of energy at those wavelengths (1).

In the visible light spectrum, there are seven distinct colors that the human eye can identify. They are violet, indigo, blue, green, yellow, orange, and red. The wavelengths of all these colors are different. The colors with larger wavelengths have a lower level of energy. On one side of the spectrum is violet, with a wavelength of 430nm to 390nm, and on the other side of the spectrum is red, with a wavelength of 750nm to 650nm (2).

The concept of color can be very confusing when describing the specific color and how you can obtain it. There are two types of color systems. One of the color systems is that in which colors are generated by light. And the second color system is that in which you can actually touch, these colors can be seen on the surface of objects or on the printed page(3).

In the system in which color is generated by light, the three primary colors are red, green, and blue. When any two of these colors are combined they a secondary color is produced. When red and green is mixed yellow is produced. When blue and green is mixed cyan is produced. And, when red and blue is mixed magenta is produced. When all three primary colors are combined white light is produced. This is called the additive process of combining colors(3).

In the system in which you can actually touch the color, the three primary colors are red, yellow, and blue. When any two of these colors are combined they a secondary color is produced. When red and yellow is mixed orange is produced. When blue and yellow is mixed green is produced. And, when red and blue is mixed purple is produced. When all three primary colors are combined black is produced. This is called the subtractive process of combining colors(3).

As an object we react and respond to different colors in very distinct ways. Color can control our emotions, behavior, and mood. Different cultures have also linked specific colors to specific objects. Different genders may also respond to colors in a variety of ways.

Red, one of the primary colors is at the lower end of the visible spectrum. Red can be defined for shades ranging from bright red to a dull reddish brown. The color red has many symbolizes many qualities and aspects of life. For example, red has been used to symbolize love, for instance a red rose is represents love between two people. Red also stands for good, strong health. In Scotland, red wool is applied to relieve sprains, and in Ireland it's used to relieve soar throats, and in Macedonia to prevent fevers. In China a ruby is worn around the neck to promote long life (4).

The color orange is taken from the fruit called orange. Since the fruit grows on an evergreen tree, the color became associated with fruitfulness. On the visible spectrum, the color lies between red and yellow, and has a wavelength of 640nm to 590nm. Traditionally the color symbolizes fire, lust, vigor, excitement, and adventure(4).

The color yellow, lies between green and orange on the spectrum, and has a wavelength of 580nm to 550nm. To look at, this color is the most fatiguing. This is because of its brightness; it results in excessive stimulation of the eye, thus irritating it(5). But because of its brightness, it is associated with playfulness, light, creativity, warmth, and an easy going attitude about life. It is also stands for many negative aspects, such as jealousy, treachery, cowardice, aging, and illness(4).

Green is said to be the most soothing color for to the human eye. It is the color of renewal and freshness. It became associated with fertility, abundance, and growth because it reappeared in springtime after the colorless winter. The color also represents harmony and radiates a feeling of fullness(4). In history, brides wore the green wedding gowns to symbolize their fertility(6).

Blue is located on the strong end of the light spectrum, and it has a wavelength of 480nm to 460nm. During the twentieth century blue has become associated with masculinity. Traditionally it has symbolized constancy, faith, sensitivity, peace, loyalty, and a desire to nurture. It is the color of the sky and the ocean(4).

Since ancient Roman times, purple has been associated with royalty. Kings and queens wore dark purple robes. The color symbolizes power, leadership, respect, and wealth. In the visible spectrum, purple is known as violet and indigo. It has a wavelength ranging from 450nm to 390nm(4).

Black is produced when all the colors are combined. It has always been associated with evil, and mystery. It is the color of despair, sin, and mourning. But white on the other hand is the absence of all color. It has always been symbolized with purity, goodness, light, and innocence(4).

Our eyes see the color and transmit the message to the brain. The eye recognizes each color through a three step process. Light is the source of all color. Our source of light is the sun, which we seem to think is colorless, but in reality it is a rainbow of colors. To illustrate how we see red, we will look at an example of a red apple. The first step pf the process is when the invisible colors of light shine on the apple. In the second step, the surface of the red apple absorbs all the colored light rays, except for the red ray. The red ray is reflected to the eye. In the third step the eye receives the red light and sends a message toward the brain. The brain deciphers the message, and associates each color with what that color symbolizes. (7).

Understanding color is not as complex as it seems. Color has become so much a part of our lives that we take it for granted. For us to understand color we have to first know how color is transmitted to eyes, and then to our brain. In the brain, we see that we associate different emotions with different colors. Also to completely understand color we have to comprehend the different types of colors and how they are formed.

WWW Sources

1) What is Color?

2) Color Matters- Science Electromagnetic Color

3) Color Matter- Science Color Systems

4) A Palette of Colorful Expression

5) Color Matters-Vision Color and Vision Matters

6) Color Matters-The Brain Color and Culture Matters

 

 

Continuing conversation
(to contribute your own observations/thoughts, post a comment below)

08/12/2005, from a Reader on the Web

Hi i was reading the un-authoratative paper by the student at Bryn Mawr College .... on Color Perception. I went looking for this info because my 6th grader is doing a science project along these lines . I find the paper to be in error of a couple things.... Just wanted to point them out ...in the even the student would like to correct the paper. Simply stated .... Black is NOT a combination of all colors as stated by the s tudent ...likewise. ...white is not the absence of all color. In fact ...it is the other way around. The student does state something that is contrary to the mistake ... That "light is needed to produce color"(this is correct). Corectly stated ... White is the combination of all color ... ANd Black is th e absence of light(AND ALL COLOR). Thankyou for reviewing my comments.

 

Comments

Correcting Reader on the Web's picture

light

In the wavelength only white is the presents of all colors, but in material white is the absents of all colors. This paper is about reflection of light off of material and not the wavelength of light in its state.
Take the material of cloth and in this case a shirt. One is a black shirt and one is a white shirt. Place both outside in direct sunlight (which is not absolutely white due to atmospheric distortions). The results are; the white shirt is cooler than the black shirt. The material of the white shirt is reflecting all colors back and not absorbing light; whereas, the black shirt is hot and is absorbing light.
Thus, the black shirt is the presents of all colors and white is the absents of all colors. In terms of the wavelength; a white light contains all colors and only is altered by the material that it passes through or reflects off it.
On a personal note: this is a tough subject to grip; because, it does deal with either the wavelength of light of the reflection of light off of an object.

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