Aperture, depth of field, focal length, the relationship among them?

1. Relationship between depth of field and aperture

Depth of field is closely related to aperture. When we open the aperture of the camera, we are actually narrowing the depth of field, and vice versa-this is an inviolable "iron law": the larger the aperture, the smaller the depth of field; The smaller the aperture, the greater the depth of field.

2. Relationship between depth of field and focal length

Depth of field is also closely related to the focal length of camera lens. For example, compared with a 1mm fixed-focus lens, a 5mm fixed-focus lens must have a larger depth of field than a 1mm fixed-focus lens-this is also an irrefutable "iron law": that is, the longer the focal length, the smaller the depth of field; The shorter the focal length, the greater the depth of field.

Extended data

Chinese expression of the formula of depth of field:

Depth of field = (2× diameter of dispersion circle× square of lens focal length× square of aperture value× square of focusing distance)/(4th power of lens focal length-square of diameter of dispersion circle× square of aperture value× square of focusing distance)

Back depth of field = (diameter of dispersion circle× aperture value× focusing distance)