Haidinger's brush is an entoptic phenomenon first described by Austrian physicist Wilhelm Karl von Haidinger in 1844.
Many people are able to perceive polarization of light. It may be seen as a yellowish horizontal bar or bow-tie shape (with "fuzzy" ends, hence the name "brush") visible in the center of the visual field against the blue sky viewed while facing away from the sun, or on any bright background when looking through polarized sunglasses. It typically occupies roughly 3–5 degrees of vision, about the same size as the tip of one's thumb held at arm's length. The direction of light polarization is perpendicular to the yellow bar (i.e., vertical if the bar is horizontal). Fainter bluish or purplish areas may be visible between the yellow brushes (see illustration). Haidinger's brush may also be seen by looking at a white area on many LCD flat panel computer screens (due to the polarization effect of the display), in which case it is often diagonal.
Read more about Haidinger's Brush: Physiological Causes of Haidinger's Brush, Seeing Haidinger's Brush, Use of Haidinger's Brush
Famous quotes containing the word brush:
“If you pick up some paint with your brush and make somebody’s nose with it, this is rather ridiculous when you think of it, theoretically or philosophically. It’s really absurd to make an image, like a human image, with paint, today.”
—Willem De Kooning (b. 1904)