What is depth of field and focal length?

When the lens focuses on a certain point of the object, the object at that point can be clearly imaged on the TV screen. Scenery in a certain range before and after this point can also be recorded more clearly. Beyond this range, it is not clear. In other words, the clear range of the scene shot by the lens is limited. The depth range of an object recorded "clearly" by the lens is called the depth of field.

When the lens is aimed at the subject, the clearance range in front of the subject is called foreground depth of field, and the clearance range in the back is called back depth of field. The foreground depth of field and the background depth of field together, that is, the depth of the whole TV picture from the nearest clear point to the farthest clear point, is called Quan Jingshen.

The focal length is the range from the wide-angle segment to the telephoto end.

The focal length is different from the focal length:

1, the closest focal length when the focal length is a certain focal length.

2. The focal length is the range from the wide-angle segment to the telephoto end.