Vision span or perceptual span is the angular span (vertically and horizontally), within which the human eye has sharp enough vision to read text. The visual field of the human eye spans approximately 120 degrees of arc. However, most of that arc is peripheral vision. The human eye has much greater resolution in the macula, where there is a higher density of cone cells. The field of view that is observed with sufficient resolution to read text typically spans about 6 degrees of arc, which is wide enough to allow a clear view of about five words in a row when printed text at ordinary size is held about 50 centimeters from the eyes. The brain creates the illusion of having a greater visual span by automatically and unconsciously moving the center of vision into any area of interest in the field of view.
Read more about Vision Span: Application To Speed Reading
Famous quotes containing the words vision and/or span:
“Redeem
The time. Redeem.
The unread vision in the higher dream
While jewelled unicorns draw by the gilded hearse.”
—T.S. (Thomas Stearns)
“... we’ve allowed a youth-centered culture to leave us so estranged from our future selves that, when asked about the years beyond fifty, sixty, or seventy—all part of the average human life span providing we can escape hunger, violence, and other epidemics—many people can see only a blank screen, or one on which they project fear of disease and democracy.”
—Gloria Steinem (b. 1934)