Rendering menu > Effects > Environment and Effects dialog > Effects panel > Add > Add Effect dialog > Film Grain
Film Grain is used to recreate the look of film grain in your rendered scene. Film Grain also allows you to match film grain from source material used as a background, such as an AVI, to the rendered scene created in the software. When applied, Film Grain automatically randomizes to create the look of moving frames.
The Film Grain Parameters rollout contains the following controls.
Grain—Sets the amount of grain added to your image. Range=0 to 1.0.
Ignore Background—Masks the background so that grain is applied only to geometry and effects in the scene. Choose this option when you use film (which already contains grain) as the background image.