Colors Out of Space [Slide Show]
Colors can change with their surroundings and spread beyond the lines
![Colors Out of Space [Slide Show]](https://www.scientificamerican.com/sciam/cache/file/4CF021AE-A417-42FA-9383A63E9CAA8ED4.jpg?w=590&h=393)
Colors Out of Space [Slide Show]
- WHITE'S EFFECT
In 1979 Michael White of the Tasmanian College of Advanced Education described an illusion that changed everything in visual science. The gray bars on the left look brighter than the gray bars on the right. In fact, all the gray bars are physically identical. Before White discovered this effect, all brightness illusions were thought to result from opponent processes—that is, a gray object should look dark when surrounded by light and light when surrounded by dark. But in this illusion the lighter-looking gray bars are surrounded by white stimuli, and the darker-looking gray bars are surrounded by black. The brain mechanisms underlying White’s effect remain unknown. Akiyoshi Kitaoka - MULTICOLORED RINGS
Here is another example of how the brain determines color depending on the context. In the bull’s-eye structures in the top half of the checkerboard, the center rings look either green or blue, but they are all the same color (turquoise). The center rings in the bottom half of the checkerboard are all the same shade of yellow. Unlike the previous images, this type of color illusion is difficult to explain by an opponent process because the apparent color of the rings is more similar than dissimilar to the background. Akiyoshi Kitaoka - RED RINGS
This image by Kitaoka contains a number of blue-green circular structures. The red rings are purely a creation of your brain. A process called color constancy makes an object look the same under different lighting conditions, even though the color of the light reflecting from the object is physically different. Color constancy is an incredibly important process that allows us to recognize objects, friends and family both in the firelight of the cave and in the bright sun of the savanna. Because the rings here are drawn in shades of blue, the brain mistakenly assumes that the image is illuminated by blue light and that the physically gray rings inside the blue structures must therefore be reddish. The visual system subtracts the blue “ambient lighting” from the gray rings, and gray minus blue results in a pastel red color. Akiyoshi Kitaoka - EYE SHADOW
It looks like this Japanese manga girl has one blue eye and one gray eye. In fact, both eyes are exactly the same shade of gray. The girl’s right eye only looks the same as the turquoise hair clip because of the reddish context. Part of the process of seeing color is that three different kinds of photoreceptors in the eye are tuned to three overlapping families of color: red, green and blue (which are activated by visible light of long, medium and short wavelengths). These signals are then instantaneously compared with signals from nearby regions in the same scene. As the signals are passed along to higher and higher processing centers in the brain, they continue to be compared with larger and larger swaths of the surrounding scene. This “opponent process,” as scientists call it, means that color and brightness are always relative. Akiyoshi Kitaoka
