Motion blur is the visual streaking or smearing that appears in an image or video frame when a subject or camera moves during the exposure period. In photography and film, it is a natural optical phenomenon resulting from the subject or camera traveling across the sensor while the shutter is open, with the degree of blur corresponding to the speed of movement relative to the exposure duration.

In filmmaking, motion blur is not simply an artifact to be avoided but a key element of how motion feels natural on screen. The standard cinematic frame rate of 24 frames per second combined with a 180-degree shutter angle produces a specific amount of motion blur that audiences associate with the look of film. Too little blur, as seen in high-frame-rate footage, can make motion appear unnaturally sharp and stroboscopic, often described as the "soap opera effect." Too much blur makes motion illegible. In CG animation and visual effects, motion blur must be added artificially and is carefully controlled to match the look of live-action footage or achieve specific stylistic effects. Video game cinematics and real-time 3D rendering use approximation techniques to simulate motion blur efficiently.

AI video generation models learn from vast libraries of real and synthetic footage and have absorbed the visual conventions of natural motion blur. When generating action sequences, fast camera movements, or dynamic scenes, well-prompted AI video models typically render motion blur in ways consistent with cinematographic norms. Specifying "fast camera pan with natural motion blur" or "high-speed action with cinematic motion blur" in prompts can help reinforce this expectation when the generation calls for it.