What is Colour Summary

Question 1

Why do we need more than one photoreceptor to see colour?

Answer 1

The need for more than one photoreceptor to see colour is due to the principle of ‘univariance.’

Question 2

What is the principle of univariance?

Answer 2

The principle of univariance states that a single type of photoreceptor can only convey information about the number of photons absorbed,

• but cannot distinguish between different wavelengths of light.
• Thus, multiple photoreceptors with different spectral sensitivities are required to perceive color.