Have you ever wondered how you are able to recognize a color even when lighting makes it look different? This lesson explains the retinex theory of color, including the science behind how the brain sees colors.
Definition of the Retinex Theory
We learned our colors in preschool and can tell the difference between black, red, blue, white, and other colors. We use colors to help understand and explain the differences between things. You tell your friend you live in the blue house or explain to a young child that apples are red.
Edwin Land studied light and color for many years. In 1980, he suggested an idea called retinex theory of color to explain how we are able to see colors consistently in spite of differences in light levels. It’s an explanation for how parts of the brain change the color the eye sees. The term retinex is a word he coined combining the words retina and cortex. The retina is the part of the eye that detects color, and the visual cortex is the part of your brain that processes the information it receives from the retina.
Whew! Got that? Let’s move on.The level of ambient light can change the appearance of colors. Let’s say you take two photographs of a red house, one in full sunlight and the other on a very cloudy day.
If you look at the photos side by side, you will see that the color of the house appears different. However, we know that the color of the house didn’t change, so we’re still able to confidently say, ‘The house is red.’ The camera records the colors as they actually exist for the given color, light conditions, and other camera settings. How and why does our brain do this override thing?
Causes of Retinex Theory
Our brains do this color recognition thing because doing so makes survival easier. It’s much easier to learn that a snake with a specific color combination is poisonous and should be avoided if you can recognize that color combination regardless of the current light levels.
Otherwise, to avoid a potential death, you would have to learn the specific color combination in full sunlight, overcast weather, stormy weather, winter sunlight, summer sunlight, dawn and dusk, not to mention the snake species in question will likely have color variation between individuals. Recognizing colors consistently across different ambient light levels helped our ancestors survive, and they passed that ability on to us.
The Role of the Brain
Take a look at this picture below:
The flower in the picture is the same in each photo; the only difference is the light source. We can see the color of the flower seems to change when the light source changes. How do our eyes understand and recognize the color of an object in any light source? Our eyes and brains make that happen through pattern recognition.When your eyes are open, the retina is constantly sending signals to your brain’s cortex about the actual color of light that is reflecting off surrounding surfaces.
The cortex, in turn, now needs to process this visual information. Our brains can do this because they are excellent pattern recognizing machines. The cortex scans memories for a term for the object being seen and names it. The brain also assigns the object a color from memory.
The original color sent from the retina is forgotten because the brain deemed it irrelevant information.In the previous poisonous snake example, the brain would send the signal ‘DANGER!’ and forget to mention that the retina may have actually seen something very different from the original snake color. In other words, the brain is working harder at keeping us alive than at assigning colors to objects. Luckily for us, this all happens in the blink of an eye!
Edwin Land examined light and came up with a theory to explain how objects are interpreted consistently in different light conditions.
Land’s retinex light theory explains much about colors and how humans are able to understand them. His retinex theory of color, named for the retina and cortex, explains how we are able to see consistent colors even with very different levels of ambient light, which can change the appearance of color. The theory holds that when color comes into our eyes, the information is passed through the retina to be processed in our brains. The brain names the object and attaches a color to it from memory.
The reason for this is actually not to make it easier for us to assign colors to different things, it’s to keep us alive!