What is depth of field?
1. Depth of field (DOF), refers to the relatively clear imaging range of the camera before and after the focus.
2. In optics, especially video or photography, it is a description of the range of distances that can be clearly imaged in space.
3. Although the lens can only gather the light to a fixed distance, and away from this point it will gradually blur. But in a certain distance, the degree of image blurring is invisible to the naked eye, and this distance is called depth of field.
4. When the focus is set at the hyperfocal length, the depth of field extends from half of the hyperfocal length to infinity, which is the maximum depth of field for a fixed aperture value.
Calculation of depth of field:
The depth of field is usually determined by the length of the object, the focal length of the lens, and the aperture value of the lens (relative to the aperture size of the focal length). Except at close range, the depth of field is generally determined by the magnification of the object and the aperture value of the lens.
1. When the aperture value is fixed, increasing the magnification, whether through getting closer to the camera or using a long focal length lens, will reduce the depth of field; when the magnification is reduced, the depth of field will be increased.
2. If the magnification is fixed, increasing the aperture value (reducing the aperture) increases the depth of field; reducing the aperture value (increasing the aperture) reduces the depth of field.
For some images such as landscape, it is more suitable to use a larger depth of field; however, in portrait photography, small depth of field is often used to make up the image, resulting in the so-called background virtual effect.
Because of the progress of digital image, the sharpness of image can be changed by computer, so the depth of field can also be changed by post-system.