How we see color - Colm Kelleher

Summary

This script explores the concept of physical color, explaining how light waves' frequencies determine color. It highlights the human eye's biology, particularly the role of cones detecting red, green, and blue light, which allows the brain to perceive a wide spectrum of colors, including yellow as a combination of red and green light. The script also touches on how our limited color detection in low light is due to rod cells and the practical application of color theory in TV manufacturing.

Takeaways

• 🌈 Light waves' colors are determined by their frequencies: violet for high frequencies and red for low frequencies.
• 🤔 The concept of 'physical color' suggests that color is an inherent property of light, independent of human perception.
• 👀 The combination of red and green light waves appears yellow to us due to how our eyes and brain process different frequencies.
• 🧬 Human color perception occurs in the retina, involving two types of light-detecting cells: rods and cones.
• 👁‍🗨 Rods are responsible for vision in low light, but cannot detect color, while cones are responsible for color vision.
• 🟥🟩🟨 There are three types of cone cells that correspond to red, green, and blue light frequencies.
• 🧠 The brain interprets signals from cone cells to create the perception of color, including mixed colors like yellow.
• 🌌 At night, when rods dominate, we can't perceive color because they only send a signal for light presence, not color.
• 🖥️ The principle that red, green, and blue light can be combined to create any color is utilized in TV manufacturing.
• 🎨 Our eyes have a limited number of color receptors, but this limitation allows for the creation of a wide spectrum of perceived colors.

Q & A

What is the physical basis for the color of an object?

The physical basis for the color of an object is the frequency of light waves it reflects. High-frequency light waves appear violet, low-frequency ones appear red, and the intermediate frequencies look yellow, green, orange, etc.

Why is the idea of physical color not the complete story?

The idea of physical color is not the complete story because it doesn't account for human perception. For example, when red and green light waves overlap, they create a yellow color, even though there is no yellow light present.

How does the human eye perceive color?

Color perception occurs in the retina, which contains light-detecting cells called rods and cones. Rods are for low-light vision, while cones are responsible for color vision, with three types corresponding to red, green, and blue.

Why does the overlapping of red and green light appear yellow?

The overlapping of red and green light appears yellow because the brain receives signals from both red and green cones, similar to how it would if actual yellow light were present.

How does the presence of only one type of rod cell affect night vision?

Having only one type of rod cell means that in low-light conditions, the brain can only receive signals for light or no light, which is why we cannot detect colors in the dark.

Why can the human brain be tricked into seeing any color?

The human brain can be tricked into seeing any color because it has only three types of cone cells. By combining the signals from these cones in the right way, it can perceive a wide range of colors.

What is the practical application of human color vision in television manufacturing?

In television manufacturing, instead of needing infinitely many colors, manufacturers only need to use red, green, and blue because the human brain can perceive a full spectrum of colors from these three.

How does the concept of 'red plus green equals yellow' relate to human color perception?

The concept of 'red plus green equals yellow' relates to human color perception because the brain interprets signals from red and green cones as yellow, whether from actual yellow light or a combination of red and green light.

What is the role of cones in color vision?

Cones play a crucial role in color vision by detecting specific frequencies of light and sending distinct signals to the brain, allowing us to perceive a wide range of colors.

How does the absence of a specific cone for yellow affect our perception of that color?

The absence of a specific cone for yellow does not affect our perception of that color because the brain interprets signals from red and green cones as yellow.

What is the significance of having three types of cone cells?

Having three types of cone cells allows humans to perceive a broad spectrum of colors by combining signals from red, green, and blue cones, which is known as the RGB color model.