How does a SLR camera take photos with the following effects? Blurred background and prominent characters? How to set it?

This effect is called depth of field effect. Adjusting the aperture and focal length with a SLR camera can change the depth of field. The following factors are used to adjust the depth of field:

There are three main factors that determine the depth of field:

1, aperture

When the focal length of the lens is the same and the shooting distance is the same, the smaller the aperture, the larger the depth of field range; The larger the aperture, the smaller the depth of field. This is because the smaller the aperture, the thinner the beam entering the lens, the more obvious the paraxial effect and the smaller the angle of light convergence. In this way, the converging light in front of the imaging plane will leave a smaller spot on the imaging plane, so that the scenery that was not clear from the lens has acceptable clarity.

2. Focal length

When the aperture coefficient and shooting distance are the same, the shorter the focal length of the lens, the larger the depth of field range; The longer the lens focuses, the smaller the depth of field range. This is because the focal zone (focal depth) formed by the lens with short focal length is much narrower than that of the lens with long focal length, so more light spots will enter the acceptable definition area.

3. Object distance

When the focal length and aperture coefficient of the lens are equal, the farther the object distance is, the wider the depth of field is. The closer the object distance, the smaller the depth of field range. This is because the scenery far from the lens can be clearly focused with a little adjustment, and the focus of the front and rear scenes is closely gathered. This will allow more light spots to enter the acceptable definition area, so the depth of field will increase. On the contrary, when focusing on a scene close to the lens, the distance between the front and rear focal points increases, that is, the focal depth range increases, so that the number of spots entering the acceptable definition area decreases and the depth of field decreases. For this reason, the foreground depth of a lens is always smaller than the depth of field behind it.

Extended data

Depth of field refers to the range of the front-back distance of an object measured by imaging in front of a camera lens or other imagers. Aperture, lens and object distance are important factors affecting depth of field. After focusing, the range before and after focusing, that is, the clear image presented in the range of front and rear distance, is called depth of field.