6 interesting color perception biases

Introduction

Color experiences are part sensory and part psychological experiences. The sensation of colors depend not only on physical laws related to the wavelength of the light, but also on the physiological processing in the eye and the brain. Our visual conditions and the state to which our eyes have adapted, along with our cultural background are also important contributors to our perception of colors. In the following paragraphs, we are going to talk about some of the most interesting biases that are associated with color perception.

1. Helmholtz-Kohlrausch Effect

The Helmholtz–Kohlrausch effect is a fascinating phenomenon in color perception that highlights how we interpret brightness and saturation. The effect reveals that more saturated colors tend to appear lighter to us. In simpler terms, when you increase the saturation of a spectral hue, it also seems to enhance the perceived brightness of that color. A crucial aspect of this effect is the way our eyes respond to colored light. Colored light is perceived as brighter than white light. When multiple colors are present together, the Helmholtz–Kohlrausch effect becomes even more pronounced and Colors can seem more vibrant or vivid.

The Helmholtz–Kohlrausch effect was first identified by Hermann von Helmholtz and Karl Kohlrausch in the 19th century. This effect is often leveraged in various fields such as art, design, and advertising to create appealing visuals that capture attention effectively.

2. The Bezold-Brucke shift

The Bezold-Brucke shift can be considered the opposite of the Helmholtz–Kohlrausch effect. This phenomenon describes how we perceive a shift in hue when looking at a color with higher lightness, hence the term luminance-on-hue effect. At higher light intensity, color perception shifts in specific ways: For short wavelength colors (like violet), the perception shifts toward blue. For long wavelength colors (like reds), the perception shifts toward yellow. So when exposed to bright red light, you may notice that it appears more yellowish. Conversely, under bright violet light, this hue may seem more blue.

Traditional color models, such as HSV (Hue, Saturation, Value), treat saturation and lightness as independent attributes and cannot account for perceptual changes that occur with varying lightness levels. Color appearance models (CAM), however, do incorporate perceptual aspects into their calculations. These models are designed to provide a more accurate representation of how we perceive color by mathematically accounting for factors like brightness and chromatic adaptation.

3. Simultaneous Contrast

Simultaneous contrast is an amazing phenomenon that illustrates the relativity of colors. This effect occurs when colors are placed next to one another, leading to variations in how we perceive their saturation levels. When a color is placed next to another but higher saturation color, the color appears duller. This reduction in perceived brightness occurs because our eyes adjust to the vibrant hue, making it seem less intense by comparison. Conversely, when a color is positioned next to one that has low saturation, it tends to look brighter and more vivid.

We rarely view individual hues in isolation, so simultaneous contrast has a great impact on our everyday perception of colors. For example, placing a bright red next to a muted grey will make the red appear more vibrant than if it were placed next to another bright color. Impressionists often use simultaneous contrast principles to create dynamic compositions that draw viewers’ attention. In summary, this bias demonstrates that our understanding of color is not absolute; rather, it is inherently influenced by neighbouring hues.

4. Successive Contrast

Successive contrast is a funny experience that occurs when you focus on a specific color for an extended period—typically around 5 to 10 seconds or more. Gazing at a color makes the photoreceptors in your eyes (cones) become overstimulated and build a so called afterimage which is the complementary color of the one gazed. Once you shift your gaze to a neutral surface, such as a white background, the afterimage makes the neutral wall appear colored. For example, If you focus on a vibrant red surface for several seconds, the brain compensates by interpreting signals from the less stimulated cones, resulting in seeing the wall green after shifting focus. This effect has a practical meaning as well. If one is wearing a bright pink suit, they need to account for that anyone talking to them for a longer period of time, will see their skin and face as sick neon green.

5. Purkinje Effect

The Purkinje shift is an adjustment that plays a crucial role in night vision and is part of a broader process known as dark adaptation. It refers to the tendency for our visual sensitivity to shift toward the blue end of the color spectrum in low light conditions. In dim lighting, we’re more receptive to shorter wavelengths (approximately 498 nm), which corresponds to blue light. The reason for this is that cones, the photoreceptor type responsible for vision in low light, become more active. As a result, for example reds may seem darker or less vibrant compared to blues and greens. In contrast, under bright lighting conditions, our eyes are more sensitive to yellow-green wavelengths (around 555 nm). This shift in color sensitivity allows for better visibility and contrast in low-light situations, enabling us to see objects and shapes that might otherwise be indistinguishable in darkness.

6. Color Constancy

This might be the most confusing one, as this is not a change in perception, but the perception of a color itself. Color constancy is basically consistently seeing an item with the same color despite changes in the lighting. Natural light can change dramatically throughout the day, from the warm hues of sunrise to the cooler tones of twilight. While our eyes are capable of detecting a broad range of wavelengths, they have limitations, Our ability to differentiate colors is not uniform; some colors are more easily recognized than others due to the distribution of cone cells. The resulted color constancy allows us to identify objects reliably. For example, a white shirt appears white whether you’re indoors under yellow light or outdoors in sunlight. This natural mechanism of the brain to stabilize color perception, aids us in navigating environments effectively, distinguishing between various objects and surfaces.

Conclusion

The above color perception biases are the result of a number of different factors. From the lighting in the surrounding environment to the color of the nearby object and to the condition of our eyes. In addition, the human color memory also has limitation and we often have trouble matching colors within the same environment under the same lighting conditions. We also need to count for retina fatigue when we look at the same object for a longer period of times, as the receptors get exhausted and our color perception changes. Overall, while color is often perceived as a fixed element, but in reality, it’s highly versatile. By recognizing the fluid nature of color, we can harness its potential in creative projects, making informed decisions that resonate with our audience.