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:
“we are the circle of the crazy ladies
who sit in the lounge of the mental house
and smile at the smiling woman
who passes us each a bell,”
—Anne Sexton (1928–1974)
“Yes, thou art gone! and round me too the night
In ever-nearing circle weaves her shade.”
—Matthew Arnold (1822–1888)
“When heaven and earth were in confusion hurl’d
For the debated empire of the world,
Which awed with dreadful expectation lay,
Soon to be slaves, uncertain who should sway:”
—Lucretius (Titus Lucretius Carus)