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:
“Perchance we may,
Where now this night is day,
And even through faith of still averted feet,
Making full circle of our banishment,
Amazed meet;”
—Coventry Kersey Dighton Patmore (1823–1896)
“A circle swoop, and a quick parabola under the bridge arches
Where light pushes through;
A sudden turning upon itself of a thing in the air.
A dip to the water.”
—D.H. (David Herbert)
“Behind her was confusion in the room,
Of chairs turned upside down to sit like people
In other chairs, and something, come to look,
For every room a house has parlor, bedroom,
And dining room thrown pell-mell in the kitchen.”
—Robert Frost (1874–1963)