How You See Color

How rods and cones help you see color.

Do you ever wonder why you see certain objects as blue, and others as red or orange? The answer is quite simple: we see a certain amount of wavelengths of light, which is known as the visible light spectrum. The colors that you see are actually the light that's reflected from the object, not absorbed. For example, a purple shirt absorbs all wavelengths of light except for purple, which is reflected into your eye. The rod and cone cells in your eye's retina process those wavelengths, allowing you to see specific colors.

In the human eye, light is processed by rods and cones. There are six to seven million cones, which are concentrated in a small cluster in the eye's retina. Cones allow you to see color. There are three types of cones in the human eye. Each of the three cones attracts one of the three primary colors of light: red, blue, and green. Tristimulus values measure the amount of light that hits the retina, allowing us to see color.

These values form primary colors and all non-primary colors like orange and purple. For us to see non-primary colors, the wavelengths are processed by two different cones. If you're looking at a purple shirt, the wavelength is processed by blue and red cones, resulting in tristimulus values that allow you to see purple. The retina also contains 120 million rods, which have nothing to do with color. Instead, they allow you to see at night and give you depth perception. That's why you don't see color at night: because the rods are absorbing light to help you see, but colors are not easily differentiable. So to see color, cones take the lead. They allow you to see the color of a certain purple shirt. 

The three primary colors of light and the colors that they create.

So now you know why we see color, but did you know that the same purple shirt could look totally different to your friend? In other words, both you and your friend agree that the shirt is purple, but what they see as purple could be what you see as orange. Scientists have recently determined that the color that you see as red could be seen by your friend as blue. They believe that people's perceptions of color stem from their experiences. That's why people often group certain colors with different emotions. People might think of the color red as harsh, and the color blue as calming. Scientists have determined that these emotions are a result of the wavelengths we see. So the blue wavelengths will often act to calm one down, regardless of how they see it. And the way that people process these colors in accordance to emotions have nothing to do with rods and cones. Scientists have determined that separate light detectors, called melanospin, measure the amount of light that's reflected into the eye and send messages to different parts of the brain to trigger certain emotions and regulate circadian rhythm. So if an influx in yellow light is reflected into the eye, the melanospin might send the brain a message that it's time to work and be active. 

Different types of colorblindness.

Humans can see countless colors, but everyone  processes them differently. Take people who are  colorblind, for example. They can still see color, just not as many colors as those who have all three types of cone cells. People who are colorblind don't have certain cone cells. For example, if they are missing the red cone cells, they will be unable to see red. So it's evident that some people will see colors differently or have a limited color spectrum because they do not have cone cells. Colorblindness is a single-gene condition, and it's X-linked. That means that the gene for colorblindness is found on the X chromosome, but it's also recessive. So if a man has the gene for colorblindness, then he will be colorblind because men have only one X chromosome, while women need to have two genes for colorblindness to be colorblind, since they have two X chromosomes. Therefore, colorblindness is much more common among men.

But what about those who aren't colorblind? People tend to associate color with certain objects or experiences. For example, a person who has synesthesia might see certain numbers, letters, and sounds as colors. Now this does not mean that a black and white essay will miraculously become a rainbow for someone with synesthesia. One will simply correlate a certain color with a number or a word. For example, my younger sister has synesthesia and she thinks of the color pink when she sees the number five. The language you speak could also affect the way you see color. In English, we have six basic colors which we see in the light spectrum below. But other languages refer to only two colors: light and dark. These 'colors' are grouped according to whether they are cool colors, like blue and green, or warm colors, like red and yellow. This changes the way that people refer to color. Instead of saying your favorite color is blue, you would simply say you like cool colors. That could mean purple, blue, green, or any of the numerous shades of those colors like teal or eggshell. 

The spectrum of visible light, which is the wavelengths that humans can see.

Although some languages are more vague than others when it comes to colors, we still see the same amount of them. Different animals, like dogs and cats, only see shades of yellow and blue. So they do, in fact, only see 'light' and 'dark' shades. This is because they only have two photoreceptors, or cones, in their retinas instead of three. They do not have red cones, so their vision would be the same as, or very similar to, that of someone who has deuteranomaly colorblindness, or does not have red cones.

Mantis Shrimp

In addition to not having red cones, cats have heightened abilities to see light, which gives them better vision than that of humans at night. Cats are mostly active when it's dark outside, so their eyes have more rods than human eyes do, allowing them to see more light and therefore giving them a heightened depth perception. Mantis shrimp, on the other hand, are able to see countless wavelengths in addition to the visible light spectrum. They have sixteen different color-receptive cones, which is more than five times the amount of cones that human eyes have! So manta shrimp can see colors that we have never even imagined before. They can see things like ultraviolet rays, which are simply invisible to the human eye. Imagine all the different colors that can be produced from sixteen primary colors! 

The light spectrum of humans compared to that of cats and dogs. 

There are so many electromagnetic waves bouncing around us all the time, and the visible light spectrum only makes up a small fraction of them! The only difference between different electromagnetic waves is their varied wavelengths, and the visible light spectrum just happens to have wavelengths that our eyes can detect. Color can be seen in different ways according to how living things perceive it, in addition to the makeup of their rods and cones. Language plays a huge role in the way that people see color, and it's evident that some languages place more of an emphasis on it than others. People who have synesthesia see more of an emphasis on color than those who are not syntesthetes, as color may not play a large role in their everyday lives. Especially those who are colorblind. What is most remarkable about color is that everyone sees colors differently, that what you see is red could be what I see as blue. As a result of this fact, we will never know how other people see the world.