What is depth of field (DOF)? Here are some definitions. People seem to have formed some customary notions about this term but may not really understand it. Examples of them are:
- Lens with shorter focal length (wide angle lens) has more depth of field (or less background blur) than a lens with longer focal length (telephoto lens)
- Camera with larger sensor has less depth of field compared to camera with a smaller sensor
- Depth of field can be calculated precisely from a formula and it won’t change from person to person
While these are true to some degrees, or in certain circumstances, it is not the case for all situations. If you are still confused by this subject or just want to refresh your understanding, please read the excellent article by Paul van Walree.
As Paul pointed out, the depth of field has a lot to do with human perception. Viewing conditions, distances, visual acuity, etc have significant impact on depth of field. When comparing depth of fields, it is very important to establish a comparison framework, otherwise the comparison will be meaningless. For example, wide angle lens has the same depth of field as telephoto lens when the subject is framed the same (with different perspective due to different subject-camera distance). It is also quite eye-opening to know that the lens design also affect the depth of field: some lenses with longer focal length may yield more depth of field than a lens with shorter focal length.
I hope you enjoy the reading. For more information on depth of field: