"The Illusion of Sex works by manipulating the luminance contrast between the eyes and lips and the rest of the face," author Richard Russell wrote. "It has been shown that manipulating it affects ...

While the human eye is rather poor at distinguishing between the absolute luminance ... optical illusion that when comparing or contrasting a darker image against a lighter background it looks darker.

Contrast ratio is an important criterion in screen quality. The ratio is derived by the brightest luminance divided by the darkest luminance in candelas per square meter (cd/m 2). For example ...