Single lens reflex shooting characters, blurred background, how to set?

This phenomenon you are talking about is called shallow depth of field, which means that the depth of the scene is small, so the foreground is clear and the background is blurred. There are three main conditions to realize shallow depth of field: 1 and aperture. The larger the aperture, the smaller the aperture value and the smaller the depth of field. The effect is not obvious. 2. focal length. The greater the focal length, the smaller the depth of field. The effect is obvious. 3. Object distance. The closer the camera is to the subject, the smaller the depth of field. The effect is very obvious. Therefore, according to the above rules, when shooting, you should use the largest aperture and the longest focal length, and then try to get close to the subject under the premise of both, and then try to keep the subject away from the background. This effect must be what you want. Besides, the photo of car optical flow you mentioned is very simple. As long as the ISO is set to 100, the aperture can receive about F8, and then put it on a tripod for a long time exposure. The exposure time can generally be about 4~8 seconds, depending on the actual light conditions.