Depth of field in terms of Optics

Depth of field is the distance between the nearest and farthest objects that are in acceptably sharp focus in an image captured with a camera. Depth of field is influenced by several factors, including the aperture size, focal length, and distance between the camera and the subject.

The physics behind depth of field can be attributed to the fundamental concept of the Circle of Confusion. It describes a point of light directed onto a camera's focal plane by the lens. The diameter of this dot of light might be extremely narrow when it hits the camera sensor, or it might be wider.