Wednesday, December 9, 2015

Color constancy and why some of the science is wrong

I am definitely not going to disagree with the science of color constancy, which dictates that the perceived color of an object remains constant despite changes in light. I am disturbed, however, by the insistence of some neuroscientists that color constancy and the way the brain simplifies color information cannot, under any circumstances, be disregarded or compromised.  Obviously, in their quest for fundamental rules, they are overlooking the possibility of variables in the science of vision. They are discounting the possibility that some people, especially artists, can learn to evaluate the color of the illuminant or light source and in turn learn to evaluate color more accurately.

Color constancy is a feature of color perception which ensures that the color of an object will remain relatively constant under varying illumination. Color constancy explains why the grass in your front yard looks green under blue sky, remains green under a cloudy sky, and still looks green during a red sunset. A yellow banana will always look yellow, despite any change in the light which illuminates it, and a red apple will always look red. Without the brain’s ability to discount varying light conditions, acquiring color information about objects would be difficult. Without this ability to stabilize visual information, the world would be a very confusing place.

The subjective nature of color constancy accounts for the fact that beginning artists often have a hard time seeing color. Shadows will simply look gray, and the yellow banana will be the same color yellow from one end to the other. Beginning artists are not likely to see variation in any local color or be able to adapt to changing light conditions. The idea of cooler north light vs. using a warmer studio light would be confusing. However, the ability to decipher variations in illuminants and to perceive the ensuing changes in the color of objects and the color of shadows can be learned. Most art teachers are going to know this, and so will many painters. At some point, with persistence and practice, we learn to see differently.

Can we learn to totally discount color constancy? Probably not. But we can and do learn to work with it, and in many cases we can learn to see beyond the visual system’s preference for predictable color.

We need to understand that color information relayed to the brain is dependent on the evaluation and comparison of the range of wavelengths of light reflected by different objects in the visual scene. This process allows the brain to estimate and dismiss the influence of the light source and assign a constant color to an object or surface. Color constancy is one of the many “programs” running in the background of our visual system.

The Fisherman by Joaquin Sorolla
So, how do you work around this preference for consistent color? Compare, compare, and compare. Ideally, one should evaluate the quality of the illuminant first. Is the light warmer or cooler? Compare a lit area to a shadow and decipher the difference in color temperature. Next, identify the value range. Find the lightest light in the area where you are looking, and then compare to the darkest dark. Try and grasp the relationship of the two by making a mental comparison to a value scale. Is the lightest area close to white? Or a step or two away from white? Do the same with the darkest value, comparing it to black. This is the beginning of using a different form of visual processing. View the scene as a whole, and then pick out the most obvious differences in the pieces of information contained in the whole.

Now do the same with the colors you are seeing. Look for the “warmest” color notes, those more closely aligned with red, orange and yellow, and then compare with the “coolest” information, blues, greens, and violets. Look for the most obvious differences and then try to assess the more nuanced information. Remember that this is an ongoing process and not a once-and-done thing. Once you stop looking for differences, and once you stop comparing, you will revert to normal visual processing.

And some of the neuroscientists? Well, it seems as if many don’t think artists can learn to use the brain’s ability to process and compare complex information in a different way. They don’t believe we can learn to see differently. I think this bias is compromising the integrity of their research. Believing seems to be the first step in acquiring new information. Learning to see differently comes from a place of knowing this is possible.






The Rouen Cathedral series was painted in the 1890s by Claude Monet. The paintings in the series each capture the fa├žade of the cathedral at different times of the day and year. The cathedral allowed Monet to highlight the paradox between a seemingly permanent, solid structure and the ever-changing light which constantly plays with our perception of it.