Rendering menu > Effects > Environment and Effects dialog > Effects panel > Add > Add Effect dialog > Motion Blur
Motion Blur applies an image motion blur to your rendered scene by blurring moving objects or the entire scene. Motion blur can enhance the realism of a rendered animation by simulating the way a real-world camera works. A camera has a shutter speed, and if significant movement of objects in the scene, or of the camera itself, occurs during the time the shutter is open, the image on film is blurred.
Note: In addition, you must set motion-blur characteristics for objects to be blurred using the Object Properties dialog.
The Motion Blur Parameters rollout contains the following controls.
Work with transparency—When on, motion blur is applied to objects behind transparent objects. When off, objects behind transparent objects receive no motion blur. Turning off this toggle can improve rendering speed. Default=on.
Duration—Specifies how long the "virtual shutter" is open. When this is set to 1.0, the virtual shutter is open for the entire duration between one frame and the next. The higher the value, the greater the motion blur effect. Default=1.0.