Depth of field (DoF) is a term used in photography to describe the distance between the nearest and farthest objects in a photo that appear acceptably sharp. It is one of the most important tools a photographer can use to create striking images. DoF is influenced by several factors, including:

• Aperture: The aperture is the setting that beginners typically use to control depth of field. The wider the aperture (smaller f-number f/1.4 to f/4), the shallower the depth of field will be.

• Focal length: Increasing the focal length reduces the depth of field.

• Distance to subject: As distance or the size of the acceptable circle of confusion increases, the depth of field increases.

• Sensor size: Sensor size affects DoF in counterintuitive ways. Decreasing the size of the sensor while holding the other variables constant increases the depth of field.

The transition from sharp to unsharp is gradual, and the term ‘acceptably sharp’ is a loose one. The acceptable circle of confusion size, which is defined using a property called the "circle of confusion," is used to determine what is acceptably sharp. The depth of field changes linearly with F-number and circle of confusion, but changes in proportion to the square of the focal length and the distance to the subject.

In summary, depth of field is an important concept in photography that can be controlled by adjusting the aperture, focal length, distance to subject, and sensor size. It is the distance between the nearest and farthest objects in a photo that appear acceptably sharp.