In optics, a circle of confusion is an optical spot caused by a cone of light rays from a lens not coming to a perfect focus when imaging a point source. It is also known as disk of confusion, circle of indistinctness, blur circle, or blur spot.
In photography, the circle of confusion (“CoC”) is used to determine the depth of field, the part of an image that is acceptably sharp. A standard value of CoC is often associated with each image format, but the most appropriate value depends on visual acuity, viewing conditions, and the amount of enlargement. Properly, this is the maximum permissible circle of confusion, the circle of confusion diameter limit, or the circle of confusion criterion, but is often informally called simply the circle of confusion.
Real lenses do not focus all rays perfectly, so that even at best focus, a point is imaged as a spot rather than a point. The smallest such spot that a lens can produce is often referred to as the circle of least confusion.
Read more about Circle Of Confusion: Two Uses, Circle of Confusion Diameter Limit in Photography
Famous quotes containing the words circle of, circle and/or confusion:
“Men go out to admire the heights of mountains, the huge waves of the sea, the broadest spans of rivers, the circle of ocean, the revolutions of stars, and leave themselves behind.”
—St. Augustine (354–430)
“And year by year our memory fades
From all the circle of the hills.”
—Alfred Tennyson (1809–1892)
“The confusion of emotions with behavior causes no end of unnecessary trouble to both adults and children. Behavior can be commanded; emotions can’t. An adult can put controls on a child’s behavior—at least part of the time—but how do you put controls on what a child feels? An adult can impose controls on his own behavior—if he’s grown up—but how does he order what he feels?”
—Leontine Young (20th century)