I took a few photos, some were normal, some had a vertical shadow in the middle of their faces, but there was no shadow on their faces. This is very strange. What happened?

If there is a vertical shadow in the middle of your photo, it may be caused by the following reasons: 1. Light and shadow problems caused by the position, angle and distance of people, things or lights in photos; 2. Some image sensors are blocked due to camera sensor failure or dust; 3. Damage or failure of camera parts, such as shutter. You can try to change the shooting position and angle, or adjust the lighting, time and other factors, or change the camera or repair it. In addition, sometimes converting photos into black and white images can make shadows appear clearer and help to judge their sources.