Depth of field
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The depth of field is the distance between the nearest and the farthest objects that are in acceptably sharp focus in an image captured with a camera. See also the closely related depth of focus.
A macro photograph showing the defocused effect of a shallow depth of field on a tilted page of text
This photo was taken with an aperture of f/22, creating a mostly in-focus background.
The same scene as above with an aperture of f/1.8. Notice how much blurrier the background appears in this photo.
Aperture = f/1.4. DOF = 0.8 cm
Circle of confusion
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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
Depth of field
…the nearest and the farthest objects that are in acceptably sharp focus in the image. "Acceptably sharp focus" is defined using a property called the "circle of confusion". The depth of field can be determined by focal length, distance to subject (object to be imaged), the acceptable circle of confusion size, and aperture…
An early calculation of CoC diameter ("indistinctness") by "T.H." in 1866.