The color of light can indeed affect our perception of brightness. Our eyes have different types of photoreceptor cells called cones, which are responsible for detecting and interpreting different colors of light. Cones are sensitive to three primary colors: red, green, and blue. The combination of signals from these cones allows us to perceive a wide range of colors.
Brightness perception is influenced by the intensity of light, which refers to the amount of light energy reaching our eyes. However, the perceived brightness of a light source is not solely determined by its intensity. The color of the light also plays a role in how bright we perceive it to be.
The human visual system has a characteristic known as the luminosity function or luminosity curve. This function describes the sensitivity of our eyes to different wavelengths of light. It indicates how our perception of brightness varies with the color of light.
The luminosity function shows that our eyes are most sensitive to greenish-yellow light, which corresponds roughly to the peak sensitivity of our green cones. As a result, light that contains more greenish-yellow wavelengths appears brighter to us compared to light of the same intensity but with different color compositions.
For example, consider two light sources with the same intensity—one emitting pure green light and the other emitting pure blue light. Even if both sources emit the same amount of energy, we would perceive the green light as brighter because our eyes are more sensitive to green wavelengths. The blue light, being outside the peak sensitivity range of our cones, would appear dimmer even if it has the same intensity.
This phenomenon is often taken into account when designing lighting systems, displays, and visual media. Different color compositions are used to create the perception of brightness or to evoke certain moods and emotions. By understanding how the color of light affects our perception, we can manipulate lighting conditions to create desired visual experiences.