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Color Optical Illusions

A combination of color, our perception and the structure of our eyes can result in some interesting optical illusions. Here are some examples.

After Image

Stare at the red dot.
What do you see when the image disappears?

Explanation

When the screen goes white, most people will see an after image of the US flag. When we stare at a bright object for some time, there is a fatigue of the retinal process. Because of this fatigue, when the image disappears, we see the complimentary color. The complimentary color may linger for some time until the retinal process dies out.

Color Perception Optical Illusion

How many colors are there in this picture, not including white?

A discussion of color and optical illusions.

Explanation

If you answered two, you're correct. A close inspection will show that the "new" colors in the middle are actually not new. They are perceived to be different because the two colors are placed next to each other.

The darker colors that seem to appear are caused by a dithering effect. Dithering occurs when colors are so close together that your eye mixes them to create a new color.

Color Dot Optical Illusion

Which circle is largest? Which is smallest?

Explanation

All of the color dots are the same size. Color sensation is due to changes in the frequency of light that is detected by our eyes. Here's a link to a site discussing information about color, and it's potential to affect health.

Flag Color Optical Illusion

What is the difference between the two shades of green?

Explanation

There is no difference. It is the same shade of green. If you don't believe it, cover up the other colors and you'll see that they are the same.

Our perception of color is affected by the contrast with the nearby colors. Here the other colors strongly affect the green to make it appear different.

Color Reading Optical Illusion

Read through this list of colors. But instead of reading the word,
speak the color of each word.

Explanation

If you are like most people, you found this exercise to be hard. This is known as the Stroop Effect. There is a conflict between what we read and what we perceive. Orange should not be blue. Indigo should not be gray. It is also possible that this task is difficult because it requires both hemispheres of our brain to work together.

Blue and Yellow Spinning Wheel Optical Illusion

What do you see when you stare at this high speed animation?

Do you see any other colors besides blue and yellow?

Explanation

Because of different types of computers and monitors, this illusion may be more or less pronounced. If this illusion is drawn on a piece of paper and spun around, there can be some interesting color effects.

The color effects seem to be related to how fast color can be sensed in the cones of our eyes. Blue seems to be detected the fastest, while green seems to be detected the slowest. Red is in the middle. These effects can even be seen if the two colors are black and white.

Block Contrast Optical Illusion

Which block is larger?

Explanation

They are the same size. The perceived size of an object is affected by the color surrounding it. Also, in this illusion, the framed object grabs more attention, making it seem larger.

Circle Contrast Optical Illusion

Which of these two dots is larger?

Explanation

Both dots are the same size.This optical illusion shows how different colors can make a circle look different.

White Balance

The quality of light, even what we would consider white light, changes significantly depending on the light conditions. The effect is so pronounced that cameras need to adjust for the difference in a process called "white balancing," or the resulting photos can look terrible.

Our eyes automatically adjust or "white balance," usually over a period of several seconds. This illusion of a gray, hazy dot is a good example of this process, which is related to the after image illusion of the flag we saw above. If you stare at the center black dot in this illusion, you will notice that the gray haze surrounding it eventually "white balances" and appears perfectly white.