How do see color

Rather, the surface of an object reflects some colors and absorbs all the others. We perceive only the reflected colors. Thus, red is not "in" an apple. The surface of the apple is reflecting the wavelengths we see as red and absorbing all the rest. An object appears white when it reflects all wavelengths and black when it absorbs them all. Red, green and blue are the additive primary colors of the color spectrum.

Combining balanced amounts of red, green and blue lights also produces pure white. By varying the amount of red, green and blue light, all of the colors in the visible spectrum can be produced. Light travels into the eye to the retina, located on the back of the eye. The retina is covered with millions of light receptive cells called rods and cones. When these cells detect light, they send signals to the brain.

Most people have three kinds of cone cells, and every color stimulates more than one cone. Their combined response produces a unique signal for each color, and millions of different colors can be distinguished this way. These cells, working in combination with connecting nerve cells, give the brain enough information to interpret and name colors. Considered to be part of the brain itself, the retina is covered by millions of light-sensitive cells, some shaped like rods and some like cones.

These receptors process the light into nerve impulses and pass them along to the cortex of the brain via the optic nerve. Have you ever wondered why your peripheral vision is less sharp and colorful than your front-on vision? It's because of the rods and cones. Rods are most highly concentrated around the edge of the retina. There are over million of them in each eye. Rods transmit mostly black and white information to the brain. As rods are more sensitive to dim light than cones, you lose most color vision in dusky light and your peripheral vision is less colorful.

It is the rods that help your eyes adjust when you enter a darkened room. Okay — back to color vision and a real-life example. Imagine you are outside in an apple orchard at noon on a hot, bright day. How do you know if the fruit you are about to pick is ripe? The light from the sun is bouncing off an apple and then after the bounce, it enters your eye.

Ripe apples contain a special chemical in their skin, and during the bounce, that chemical absorbs some of the sunlight spectrum. It does not absorb all the wavelengths equally though — the short wavelengths are blocked but most of the long-wavelength light is reflected straight back out toward you. In other words, the bounce causes the spectrum of the sunlight to change and now it has much less short wavelength light in it. The riper an apple is, the more of this color absorbing chemical it has in its skin, and the more short wavelength light it absorbs.

To understand this message, we do not have to know exactly what the spectrum of reflected light looks like. We just have to know that it has lots of long wavelength light in it, and not so much short wavelength light.

This is where our cone cells come in. Each of the three cone types gets excited by a different part of the light spectrum — in other words by a different set of wavelengths. The M cones will be slightly excited because there are some medium wavelengths, but the S cones will be silent because the spectrum contains almost no short wavelengths — the apple skin absorbed them all.

Each cone will then send a message to your brain telling it exactly how excited it is. So when that big group of millions of different light waves bouncing off the apple goes into your eye and hits the millions of cone cells at the back, it generates just three signals: high, medium, and low at every location. And this is how color works for pretty much everything we see.

Each object reflects light into our eyes, and that reflected light creates responses in our L, M, and S cones. There are thousands and thousands of L, M, and S cones in your eye, each sending a coded message to your brain telling it how much long-, medium-, and short-wavelength light is bouncing off all the different things that you can see.

These three types of signals tell you about what stuff each object is made of — and this three-number code is what we call color. Light is a special case because we see its spectrum without it bouncing off anything, but the same ideas apply and its color is still due to the different amounts of signal that it generates in three cones. You might have noticed that we tried not to mention the word color until the very end of this explanation.

The idea that color is only in your head might seem strange at first, but think of it as being a bit like pain. Now you might have spotted a problem with this system. We would like to use color to tell things apart, but the only thing that you really know about the color of an object is the three-number code that it generates in your cones. It means that any two sets of light rays that make your cones respond the same way will look identical, even if they contain quite different wavelengths.

In theory, this is correct, and there are some occasions when you will mistake two different objects that seem to have the same color. Luckily, this happens less than you might think — it is not a big problem.

Even better, being able to mimic the color of one thing in real life using a different set of wavelengths turns out to be fantastically useful.

Imagine you have measured the exact spectrum of an apple, and you want to show a picture of that apple on a TV screen. TV screens are made of lots of little lights, arranged into a pattern that repeats over and over again.

It was only confirmed in the s, which means this level of detail in understanding wavelengths and colors is only 60 years old. Today, seeing a yellow school bus is a common sight. The school bus yellow is actually found in the middle of the wavelengths that trigger our perception of red and green. When light hits an object, some of the spectrum is absorbed and some is reflected. Our eyes perceive colors according to the wavelengths of the reflected light.

We also know that the appearance of a color will be different depending on the time of day, lighting in the room, and many other factors. They may perceive different variations of the color based on a range of factors—including their lighting. These tools—from spectrophotometers, to software to services, ensure color evaluation stays objective no matter what.

Most of us can recognize the color of familiar objects, even as lighting circumstances change such as a yellow school bus. This adaptation of the eye and brain is known as color constancy. We might also be able to agree with each other on the wavelengths that define basic colors.

However, this might have more to do with our brains than our eyes. For instance, in a study at the University of Rochester, individuals tended to perceive colors the same way, even though the number of cones in their retinas varied widely. But things get much more complicated when individuals or multiple people try to match colors tto a product or material samples. Physical or environmental factors and personal differences between viewers can alter our perception of color.

These factors include:. To complicate matters further, the phenomenon of impossible colors, chimerical colors and more exist and can wreak havoc on a business that relies heavily on accurate color readings. Using instruments to accurately detect colors from samples and products is imperative and having inter-instrument agreement is even more so. ThoughtCo does a good job of explaining the impact of these factors.

Colors play a vital role in our everyday lives. Like the yellow school bus. Why is it important that we see it, even in our periphery? For safety, of course. Many colors are used to depict important messages without words. Red stop signs and green traffic lights are universal. These and other regulated colors play an important part in our lives. We also associate colors with pride.