The Wonderful Journey of Depth of Field (DOF) from Lens to Imaging

When photographing an object, the lens used often adopts the form of a lens group to eliminate aberrations and optimize the imaging effect.

In the optical path model, it can be approximated as a single lens. In the imaging process, according to the properties of the lens, the relationship between the object distance and the image distance satisfies the thin lens formula.

When the object distance increases, the distance will decrease accordingly. In the camera, since the position of the detector is fixed, when the lens is determined, the optimal object distance, that is, the working distance of the camera, is often obtained.

When the subject moves forward and backward at the optimal working distance, the imaging point will also move forward and backward of the detector, and it cannot be clearly focused on the detector, so the image is blurred.

The circular spot formed is called the circle of confusion, and the distance that can still ensure that the image can be resolved after moving forward and backward is called the depth of field. The depth of field is composed of the front depth of field and the back depth of field.

When the subject is at the depth of field limit, the size of the circle formed on the detector is the maximum allowable circle of confusion.