Screen tearing

Screen tearing is a visual artifact in video display where a display device shows information from multiple frames in a single screen draw. The artifact occurs when the video feed to the device is not synchronized with the display's refresh rate. That can be caused by non-matching refresh rates, and the tear line then moves as the phase difference changes (with speed proportional to the difference of frame rates). It can also occur simply from a lack of synchronization between two equal frame rates, and the tear line is then at a fixed location that corresponds to the phase difference. During video motion, screen tearing creates a torn look as the edges of objects (such as a wall or a tree) fail to line up. Tearing can occur with most common display technologies and video cards and is most noticeable in horizontally-moving visuals, such as in slow camera pans in a movie or classic side-scrolling video games. Screen tearing is less noticeable when more than two frames finish rendering during the same refresh interval since that means the screen has several narrower tears, instead of a single wider one.