The Cornsweet illusion, also known as Craik-O'Brien-Cornsweet illusion or Craik-Cornsweet illusion, is an optical illusion where the gradient within a central line or section creates the impression that one side of the image is in fact darker than the other. In reality, both sections are the same.
The Cornsweet illusion, as well as numerous other visual and perceptual illusions, provide a valuable way to investigate how the eye and brain process visual information. Equally, they are used by artists for visual effect, entertaining and satisfying the endless fascination human beings have with novelty and creativity.
The Cornsweet illusion, also known as Craik-O'Brien-Cornsweet illusion or Craik-Cornsweet illusion, is an optical illusion that was described in detail by Tom Cornsweet in the late 1960s, and published in 1970 in 'Visual Perception'. Craik and O'Brien had made earlier observations in a similar vein, and thus the illusion is often referred to as the Craik-O'Brien-Cornsweet illusion.
When looking at the classic Cornsweet illusion, two squares of differing contrast appear to be separated by a thin band of gradient. In reality, the two squares are exactly the same level of contrast. In some examples, the illusion is so convincing that the only way it can be believed is to cover over everything but the two identical colors, thus proving that they are indeed the same.
This phenomenon is similar to the familiar phenomenon of simultaneous contrast and Mach bands, but differs from it in two important respects.
The Cornsweet illusion is an example of the way the brain uses the edges of shapes to impart information to the surrounding areas, and takes place because of the way nerve impulses travel through the visual cortex. The retina interprets what it sees using certain luminance profiles. The Cornsweet image is processed with nearly identical codes, which the cortex then integrates and arrives at the same perceptual result. In other words, the brain is used to seeing things a certain way, and often interprets information within those parameters.
The Cornsweet illusion has applications in graphic design, where it can be used to create interesting visual effects. Awareness of the Cornsweet illusion is also useful in areas like radiology; without awareness of the Cornsweet illusion, technicians can potentially misread areas of x-ray images.
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