What is the depth of field of photography and what does the depth of field of SLR camera mean?

When we focus on a certain point in the scene, the image taken by this scene as a scene in a certain range before and after the focus point is relatively clear. This kind of "clear range before and after the scene image" is called depth of field. In other words, the depth of field is the clear range of the depth of the scene image, or the distance between the "clear scene" before the focus and the "clear scene" after the focus is the depth of field. The clear range (distance) of the depth of field is large, which is called "large depth of field"; This small range (distance) is called "small depth of field". The depth of field in photography practice plays a very important role in the artistic effect of a photo, so it is very important and necessary to master the technology of controlling the depth of field.

There are usually several methods to control the depth of field:

Aperture control

The aperture is inversely proportional to the depth of field. Large aperture and small depth of field; Small aperture and wide depth of field. Therefore, in a work, if you want to make the scene image clear and wide, choose a small aperture in the exposure combination; If you want the middle scene in the photo to be clear and the foreground and background to be blurred, choose a large aperture.

remote control

The shooting distance is proportional to the depth of field. Large (far) distance and large depth of field. Small (near) distance and small depth of field. However, the relationship between focal length and depth of field is conditional, that is, the focal length is within the "hyperfocal distance", otherwise, the relationship between them will become inversely proportional. About "hyperfocal distance" ("hyperfocal distance" for short), we will talk about it in detail below, so I won't say much here.

Choose different focal lengths for lens control.

Lenses with different focal lengths control the depth of field, which is inversely proportional. The lens has long focal length and small depth of field; Short focal length and large depth of field.

It must be clear here that the three conditions that control the depth of field, such as aperture, camera distance and lens focal length, are influenced by these three conditions at the same time for a shooting scene, and they interact with each other. Either way, the other two are prerequisites. Therefore, in shooting practice, the conception and requirements of depth of field must consider these three factors that affect depth of field and use them comprehensively. However, it is common and convenient to control the depth of field by using the aperture size.