Relationship between aperture and depth of field

First of all, the basic function of the aperture is to adjust the amount of light entering the camera. By changing the aperture size, the amount of light entering the camera per unit time is controlled, that is, the exposure of the photo is controlled, so as to control the brightness of the photo. Therefore, the larger the aperture, the more light per unit time, the greater the exposure and the brighter the photo. Conversely, the smaller the aperture, the darker the photo.

Depth of field refers to the clear range of the scene before and after focusing. Large depth of field is called large depth of field, and small depth of field is called small (shallow) depth of field. Generally, there are three main factors affecting the depth of field, namely, the distance between the subject and the lens, the focal length and aperture of the lens.

As can be seen from the above three comparison pictures, the smaller the aperture (f/8, small aperture), the clearer the face behind; The larger the aperture (f/2.8, large aperture), the more blurred the face behind. Another point is that the position of focus will also affect the position of depth of field. If the focus of the f/2.8 picture is the second face, then the faces of 1, 3,4 will become blurred, and the faces in focus will remain clear.

So we can also draw a conclusion: the larger the aperture, the smaller the depth of field (shallow); The smaller the aperture, the greater the depth of field (depth). Of course, the relationship between depth of field and distance can be well understood; The closer the distance, the smaller the depth of field; The farther the distance, the greater the depth of field. Small depth of field means that the clear range of the scene before and after focusing is relatively small, and large depth of field means that the scene in a large range before and after focusing is very clear and visible.

When and what aperture/depth of field should I use? It can be said that this is not absolute, and it depends entirely on personal needs, but usually landscape notes use deep depth of field (because they want the whole landscape to be clear and sharp) and portrait photos use shallow depth of field (because they want people to stand out in phase), but it should be noted that landscape photos can also be created with shallow depth of field, and portrait photos can also use deep depth of field, so which depth of field to use depends entirely on the needs.