When we hear the phrase depth of field, most of us instantly relate it to aperture. Yes, aperture plays an important role in controlling depth of field, but it’s not the only factor. Adorama‘s Mark Wallace explains that there are three main factors that control how much of an image is in focus:
The relationship between aperture and depth of field is something that most photographers learn during their early days with the camera. If you set your aperture wide open using values like f/1.4 or f/1.8, the lens can only focus within a very thin zone; it will have a very shallow depth of field. The foreground and background will be blurred out while the subject will be in focus.
But if you close down the aperture by using values like f/16 or f/22, the lens will have most of the scene in focus; it will have a greater depth of field. The resulting image will thus have less blur in the foreground and background.
2. Focal Length
If the camera-to-subject distance and the aperture are kept the same, a lens with a longer focal length has shallower depth of field than a lens with a shorter focal length (i.e., the longer focal length will have less of the area in focus and produce more blur than a lens with a shorter focal length). Compare the background blur in the images below:
3. Camera to Subject Distance
All lenses have minimum focusing distance. They produce greater blur when the subject-to-camera distance is close to the minimum focusing distance. If the aperture and focal length are kept the same, the same lens will produce more blur when the subject is close to it than when the subject is farther away. This is to say that a lens will have greater depth of field when the subject is farther away and a shallower depth of field when it is close to the subject.
Go ahead and try out the combination of these three factors to gain better control over depth of field.
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